Alternator bypass & engine preheater mod
 

I have a 2002 VW Golf 1.9 TDi estate, and I'm planning to get some mpg gains by not using the alternator to generate electrical power but using an onboard leisure battery to do the same job.

This would involve plugging the car into the mains every night to charge up the leisure battery, so I thought it would make sense to also pre-heat the engine every night/morning using the same electric hook-up. This will reduce the strain and wear on the engine at start-up and improve the mpg I get in the first few miles. Cold engines also pollute more. The engine pre-heat is of more benefit in the winter of course but will save fuel and reduce wear all year round. An added benefit is that I get to start the day in a WARM car with frost-free windows!

I'm hoping for about 10% improvement in mpg following this combined mod. But whatever improvement I get (and I will certainly get some) the added benefits of reduced engine wear and increased comfort convince me it is worthwhile in any case.


The possible downsides of the plan are...

1. Increased weight. Maybe 30kg. (Battery, etc. fits below rear load floor.)
2. Cost. This mod may not pay for itself, ...and batteries are consumables.
3. Added complexity.


Upsides summarised are...

1. Improved mpg.
2. Lower pollution at start-up
3. Greatly improved comfort, safety and time-saving on winter mornings.
4. Reduced engine wear.
5. Insurance against main starter battery failure or alternator failure (battery backup!)
6. Main starter battery is also charged fully every day.


The basic plan is to leave the normal starter battery as it is and to use a second, auxilliary battery of the deep-discharge type (i.e. a 'leisure battery') to replace the function of the alternator. The 12 volt leisure battery will charge the main battery via a dc/dc converter set to somewhere between 13.8 and 14.4 volts output (to be decided.) That way, the voltage the car's components see will be the normal 14.x volts and not the 12 volts or lower that it might see using just one partially-discharged battery. Also, the starter battery will remain fully charged at all times. To keep things simple to start with I'm planning to have a simple on/off switch for the alternator and a simple on/off switch for the dc/dc converter. Later on I might automate the system so at certain voltage levels in the auxilliary (donor) battery the dc/dc converter switches off and the alternator simultaneously switches on.

(At some point in the future I may consider permanently bonding one of those flexible solar panels on the roof of the car to increase the alternator-free driving range, but that's expensive and won't help for for daily short journies. It can easily be added to any planned system that incorporates a storage battery so I'll ignore solar power for now.)

So anyway I decided to document the process, and post some of that process up here, in the hope that someone might be able to point out my errors before I make them!

OK, so apart from research, all I've done so far is to identify the field wire to the alternator, cut into it and put a pair of bullet connectors in line so I can disconnect for testing and then connect in a switch to turn the alternator on and off from inside the car. Identifying the wires wasn't so straightforward (for me!) and involved a good bit of reading up on how alternators work. In my car, there are three wires (disregarding the -ve ground connection) connected to the alternator:

1. A big fat wire that routes to the battery via the starter motor. This carries the charging current.

2a. There are two smaller wires that terminate in a two-pin plug to a socket on the alternator body. One of these will be the +ve battery voltage 'reference' wire, which the alternator uses to monitor battery voltage.

2b. The other small wire in the two-pin connector will be the field wire, which is live when the ignition switch is on, and is used to 'kick-start' the alternator by energising the rotor's magnetic field.

The field wire is also in series with the dash warning 'no charge' light (battery symbol) and that's how I identified it. I disconnected the two-pin plug and grounded each of the two pins in turn, both with the ignition on and with the ignition off. I didn't want to risk grounding it 100% so I put a multimeter in series on the amps scale as that has a fuse (of which I have plenty of spares!) I think you could just use a test light bulb, but I didn't have one. The field wire is the one which lights up the 'no charge' warning light when it is grounded.

After cutting the field wire and putting the bullet connectors on, I reconnected the two-pin plug and checked with a volt meter plugged into the cigarette lighter socket. Sure enough, the alternator was not charging when that field wire was disconnected, as volts remained down at about 12.5v even when the engine was running. Success! That's the only alteration of the car's electrical system I need to make.

So the next step is to MEASURE the electrical current my car actually uses in various states: how much it uses just to keep the engine going, how much the lights use, the heater blower, the radio, everything. I need that data in order to determine what size auxilliary battery to fit, what size mains charger, what size dc/dc converter, etc.

I could have used my multimeter to measure the current used but it would have been tricky, involving disconnecting and reconnecting cables while the engine is running, and of course the risk of blowing fuses in the meter. (http://ecomodder.com/forum/showthrea...olts-8908.html) So I went out and bought a small DC clamp meter that will measure down to 1mA and up to 80A. That cost £82 but I will certainly use it for other things. Measuring current is always a pain if you have to disconnect things every time.

In the next post I will list the current draw for all the equipment on my car including the engine...

I can't speak for motorists in other locales, but here in the Rust Belt the engines and transmissions are typically the last things to fail. Everything on the undercarriage succumbs to rust and falls apart and the drivetrain is still going strong. I've had cylinder heads off engines with nearly 200,000 miles on them that had virtually no ridge and still had clearly visible cross-hatching- easily good for another 200,000. Just sayin', engine longevity doesn't seem to be much of an issue anymore.

P.S. Unless it's a VW.

Good point Frank. It's pretty damp and salty around here too. I'm currently sorting out some rust on the underbody because I am planning on keeping this car for as long as possible. Encouragingly, the only rust I've found so far has been where accidental damage has taken place, such as previous owners dropping the sills on kerbs or jacking up on the wrong places. Elsewhere, it all looks 100% rust free, which is not bad after 11 years on Britain's salty roads. I also took off one of the front wheel arch plastic liners and found half a kilo dry weight (more than a pound) of compacted mud filling the lower rear section of the wheel arch. It was full to a depth of about six inches. That mud will have been almost constantly damp and soaked with road salt for years. No rust whatsoever underneath.

And I'm not having to start at -30 degrees C, so engine wear is probably not a huge issue, as you say. Still, eliminating any possible wear from cold starts is a kind of 'free benefit' of doing this mod and it cheers me up to count the benefits!

The mpg benefit of starting the day with an already-warm engine is my main motivation for fitting the pre-heater. In the summer, the car's mpg meter will show about 70mpg on my five mile run into town, and on the way back it will show about 90mpg (imperial) even if the car has been sitting an hour or two in between. (In the winter I would expect this difference to be even greater.) With an already warm engine it should be showing close to 90mpg both ways. (The car's mpg meter is about 7% optimistic, but consistently so.)

Yes, absolutely, I should have noted before that all the other aspects are well worthwhile... and the engine wear thing is nice too, even if it doesn't really matter.

I'm doing something similar, but with a different strategy:
http://ecomodder.com/forum/showthrea...tml#post384677

I haven't looked, but I am sure a 12V DC-DC converter capable of car level amperage is going to be rather expensive. You really have to know what demands your car has, and make sure your DC-DC converter can supply more. Also, DC-DC step up conversions increase voltage but you loose some current in the process. Be sure to know exactly how much current is reduced at the output. It will factor in your calculations to figure out how long the deep cycle can charge and run your system.

The only reason (that I can think of) to stay at 14 volts is headlight dimming. The cars electronics will run fine on 12V. Deep cycle batteries often have sufficient CCA ratings to start our little engines, so that isn't a concern unless your under extreme demands on starting. You'll have to decide if the dimmer headlights are still acceptable safety wise. For my car 14V vs 12V is a noticeable difference, but just because you notice the dimming doesn't mean its unsafe. Faded lenses and old bulbs are more of a safety risk than running headlights on 12V in my opinion.

There is also problems with running multiple batteries in the car. For your system it's a bit different so it may not apply. If I were to simply connect a deep cycle in parallel with my starter battery I run the risk of damaging the starter battery. Those batteries are not designed to discharge much at all. If I run them in parallel they share a voltage and combine capacity, but I am still discharging it more than I would want to everyday. This could cause it to go bad earlier, further making my system inefficient and costing me more in batteries. Having a single deep cycle, or multiple deep cycles in parallel provides a more flexible setup with discharging.

Overall I think cutting out the alternator could yield good MPG results, but it probably won't be economical overall. When you factor in the cost of batteries, the cost of the extra components, and then the cost to charge the battery from your house, there is very little room for any actual savings. But for me it's not all about actual savings. Some of it is just seeing how high my MPG number can go, regardless of what it costs. If that is you too, then go for it.

Thanks cbaber,

Absolutely. So I'll be measuring my amps usage in the next couple of days, and then I can decide on size of battery/size of dc/dc converter, etc. So far I have found one UK company who makes suitable dc/dc converters designed for charging one battery from another. They make them modularly at 12amps; 24amps; 36amps; 48amps, and so on. From memory about £70/module. They will put out a predetermined voltage and shut off with an audible alarm at a predetermined donor battery voltage. Because they make them locally they can set those voltage levels to whatever I want, within limits.

Another possibility is these dc/dc boost units available from Hong Kong on e-Bay. 10 amp units, sold as a bare circuit board on a heatsink with no case. They have adjustment screws for regulated output voltage and I believe they have a contact for remote switch on/off. Up to 95% efficient, so they claim, and any number of these 10A units can be run in parallel. They look good to me and cost £12 each delivered to the UK. Three of those units would cost £36 and put out 30A. I'm sure that would be more than adequate. (I am, after all, only having to provide the average power needs through the converter, as any peaks will be taken from the starter battery.)

I'll probably go with the UK firm though because a guy in the tech support department there is an mpg nut himself and would be keen to help me get this working well. He was giving me advice about LED lighting. I also like the idea of the automatic shut-off alarm at low donor battery voltage. I'm told it can extend battery life significantly if you don't go down below 50% charge. Also I can use that shut-off signal to poke the alternator back into life automatically.

But this all depends on the data. I was playing with the clamp meter tonight. It hooks nicely over the battery's earth cable and seems to work well. Maybe not quite as accurate as a multimeter in series, but they say it's accurate within 3% or so, and that's good enough for my purposes.

...PS - I just read your thread. So you removed the alternator/power steering belt completely, eh? Power steering delete (or fitting an electric p/s pump) is also on my list to do, but one thing at a time... I like the battery relocation you've done but I'm wanting to go down the two-battery route. I was nervous about having a long cable run to the starter in a diesel. At 300A cranking current you'd need a monster cable for such a long run. As it is, I think I can safely use the existing cable to the 12v power outlet socket in the load area as that is fused at 35A and I doubt my dc/dc converters will be rated higher than that. I'll just plug the converter in there to start with.

My 2nd battery is going to be located down in the spare wheel well and the spare wheel is going to stay at home. I thought about the 'no spare wheel' issue a long time and it does make me slightly nervous as I did lose a wheel in an accident a year or so ago in the snow. Tyreweld would not have helped in that situation. But it's rare these days. That was the first time I'd had to change a wheel by the roadside in 20 years. In that time I've had quite a few breakdowns due to faulty batteries and alternators, as well as other breakdowns for other reasons. Tyres are tough. If they're in good condition and you drive carefully I reckon they're no more likely to let you down unexpectedly than any other component. With two batteries (and all the voltage and current monitoring guages I'm going to have on the dash!) I'm far less likely to find myself with a dead battery or be caught out by a failing alternator.

On my engine the accessories are driven by their own belt. So I can remove just the power steering belt and not worry about effecting or modifying the other systems. The cable I used was 2 gauge welding cable, which can handle my Honda's starting amps. For 300A I would have used 0 gauge welding cable. Yes it's a pretty big wire, but the safety component is the inline fuse mounted just next to the battery. If anything were to short out on the long cable run that fuse would protect the car from a fire.

I'm willing to bet that during normal operation your car uses more than 35 amps. Especially at night with the headlights on. I could be wrong though, as I have not measured my own current draw. But it does pose a problem if you plan on using the existing 35 amp outlet. Your DC-DC converter has to provide the current to run the car systems, but also a little more to make sure the starting battery stays topped off.

It is true that how much you discharge the battery is related to how many cycles it can perform and how long it lasts. Even deep cycle batteries, which are designed to be deeply discharged, will last longer if you discharge down to 50% capacity rather than down to 20% capacity. That is one of my concerns as well. My deep cycle battery may not even last 2 years if I go through 300+ charging cycles a year. So I may end up spending 2-3 times more on batteries than I would without deleting the alternator.

Well one option is to buy a leisure battery with a 4 or 5 year warranty. Most leisure batteries get used just a few times in a year so manufacturers can afford to offer long warranties like that, even though they only expect them to last for 500 full charging cycles.

Well, I now have some data for how much electrical power my 2002 1.9 TDi PD VW Golf uses.

I parked up today, disconnected the alternator field wire and started measuring. I used my recently-acquired DC clamp meter, which I later checked against my two digital volt/amp meters and found to be reasonably accurate. If my DVM's are accurate (they both agree) then the clamp meter over-reports DC current by 2% at about 2A and by 3% at about 7A. That's within specification and accurate enough for my purposes.

With the alternator disconnected, the battery voltage was about 12.3v. At higher voltages (e.g. 14.4v) the current draw will be correspondingly higher. E.g. If a test shows 12A at 12v then at 14v the current draw would be 12A / 12v x 14v = 14A. A 24A draw at 12v would become 28A at 14v and so on. This is assuming the loads are simple resistive loads like light bulbs kind of are.

(By the way, just two bulbs have already been swapped out for LED's: the two 5w rear number plate bulbs. All other bulbs are standard incandescant filament bulbs. One of the four 5w rear tail light bulbs is blown and needs to be replaced. I am assuming the two LED's use 20% of the power of the 5w filament bulbs, so that's 8w saved, plus the 5w of the blown bulb makes 13w. So I have added 13w (call it 1.0A) to any test results where the lights are switched on. I intend to replace all the bulbs I can with LED's but I want to start with a baseline current requirement assuming the use of standard bulbs. Later I can calculate how much lower the requirement will be using LED's.)

So, with all the doors closed, the bonnet ('hood') up and the meter clamped around the battery's ground wire I got these results. The bonnet has no electrical connections to it as far as I know so the car is not 'aware' it is up and its being up does not affect the car's current draw in any way.



Ignition off...

Key out of ignition, car unlocked ...... 0.025A
Key out of ignition, car locked ........ 0.020A
Key in; ignition off; sidelights on .... 3.7A


Ignition on...

Ignition on; everything else off ....... 1.7A


Ignition on, plus...

Sidelights on .......................... 5.2A (- 1.7 = 3.5A)
Sidelights on; dash illumination high .. 5.3A (- 1.7 = 3.4A)
Sidelights on; dash illumination low ... 4.9A (- 1.7 = 3.2A)
Headlights on (dipped) ................ 13.2A (- 1.7 = 11.5A)
Headlights on (high+dipped) ........... 21.5A (- 1.7 = 19.8A)
Front wipers on low speed (approx) ..... 5.0A (- 1.7 = 3.3A)
Front wipers on high speed (approx) .... 7.0A (- 1.7 = 5.3A)
Rear wiper on - 20% duty x 4.5A ........ 4.5A (- 1.7 x 20% = 0.56A)
Blower on (speed 1) .................... 6.0A (- 1.7 = 4.3A)
Blower on (speed 2) .................... 8.5A (- 1.7 = 6.8A)
Blower on (speed 3) ................... 12.4A (- 1.7 = 10.7A)
Blower on (speed 4) ................... 17.5A (- 1.7 = 15.8A)
Radio on (volume = 0) .................. 2.7A (- 1.7 = 1.0A)
Radio on (volume = low) ................ 2.7A (- 1.7 = 1.0A)
Radio on (volume = medium) ............. 2.8A (- 1.7 = 1.1A)
Radio on (volume = high) ............... 3.5A (- 1.7 = 1.8A)
Radio on (volume = max) ................ 4.0A (- 1.7 = 2.3A)
Front interior lights on ............... 3.2A (- 1.7 = 1.5A)
All interior lights on ................. 3.7A (- 1.7 = 2.0A)
Engine OFF; reversing lights on ........ 5.2A (- 1.7 = 3.5A)


Engine on...

Engine on at idle (850RPM) ............. 6.4A (- 1.7 = 4.7A)
Engine on at all other engine speeds ... 6.4A (- 1.7 = 4.7A)

Engine idling; sidelights on ........... 9.6A (- 6.4 = 3.2A)
Engine idling; headlights on dipped ... 17.1A (- 6.4 = 10.7A)
Engine idling; headlights on high ..... 26.0A (- 6.4 = 19.6A)
Engine idling; blower on (speed 2) .... 22.6A (- 6.4 = 16.2A)
Engine idling; rear demister on ....... 24.1A (- 6.4 = 17.7A)


And finally...

Ignition on; field wire reconnected .... 2.1A (- 1.7 = 0.4A)



So there we have it. A few minor anomalies where results were slightly different on different occasions, but it's basically sound data I think. Sound enough for the purpose at hand anyway. Some predictable results - such as lights, where nominal wattages are already known - and some surprises.

I was pleasantly surprised that it only takes 4.7A to keep the engine going, irrespective of RPM. 1.7A is needed just to have the ignition switch on, so the minimum requirement for daytime driving is just 6.4A. Much lower than I was expecting. (I'm SURE other diesel cars I've had didn't run very long at all when I've driven them on a faulty alternator.)

The heater blower motor, even at its lowest speed, uses almost as much electrical power as the engine! (4.3A) And at its highest speed it uses a massive 17.5A! I normally drive with the blower at speed 2, which uses 6.8A, but that more than doubles the minimum day-time driving requirement. Wow! I might need to re-think that habit!

Then the wipers use about 4A (50w?) which must contribute to the higher fuel use in the rain. The rear wiper doesn't use a lot (0.56A). The rear demister uses a massive 17.7A, but I guess it's normally only on for a very short period, and when you need it, you need it.

The lights use a huge amount of power. The sidelight bulbs can all be replaced with LED's which could bring the use of sidelights down from about 3.5A (measured once at 3.2A and once at 3.7A - not sure why) to about 20% of that, which would be a mere 0.7A. That would save a useful 2.8A for all night-time driving, and at 0.7A total that would make it feasible to use daylight running lights too. (Not currently a legal requirement in the UK.)

I don't use high beam all that often but it is a shame that VW decided to keep the dipped lights on when the high beam lights are switched on. There might be a software adaptation that switches off the dipped lights when high beam lights are being used. That would save 7.5A every time the high beam lights were being used and (this might be useful for me when I'm deciding how large a DC/DC converter to use) it would reduce the maximum current draw of the car by 7.5A. At some point I'll look into what software adaptations are possible in that regard, but as I say, I don't use high beam much so I think I can probably ignore that extra current draw for now.

So, the maximum likely sustained current draw of this car is likely to be when the engine is running, radio is on, blower is on speed 2, wipers are all on low speed and lights are on dipped. Lets look at that...


Engine on ............... 6.4A
Radio on high ........... 1.8A
Blower on speed 2/4...... 6.8A
Headlights dipped ...... 10.7A
Wipers on low speed ..... 3.9A

Total max sustained .... 29.6A


I can reduce that by 1.8A by not using the radio (but I like the radio!) and I can reduce it by 2.8A by using LED bulbs in the side lights, the number plate lights and the tail lights. So with LED's installed that's 26.8A at 12.3 volts. At 14.4 volts it would be 31.4A.

The suitable DC/DC converters I have come across are either ready-made and built-for-the-purpose modular units of 12A; 24A; 36A, etc. (from a really helpful and knowledgeable local manufacturer, at a cost of about £70/module) or else impressively sophisticated and great-value-for-money bare-circuitboard-and-heatsink units of 10A each (on e-Bay, sent from Hong Kong at £12 each delivered to my door.) It looks like a 24A unit from the UK manufacturer would do the job (£140 approx) or else I could use three of the Honk Kong units (£36 plus all the other bits and pieces required to make them into useable units.)

There will always be a useful amount of buffering, or peak current supplementation provided by the starter battery, and since the alternator-free range of the car will be limited anyway, a certain amount of discharge of the starter battery would be quite acceptable at times of high current demand. By the time the auxilliary (donor) battery has got down to its 50% cut-off level, it is very unlikely that the starter battery would have lost more than 20% of its charge, and at that point, the alternator would be fired up anyway. So a 24A DC/DC converter would be adequate, and a 30A converter would be more than adequate. This simplifies the wiring somewhat as I can safely feed the current from the DC/DC converters to the main starter battery via the existing cable that feeds the 12v power outlet socket in the load area, which is fused at 35A. Indeed, as a temporary measure I can simply plug the converter output into that socket.

OK, so a 24A or 30A converter will be fine. (12A will not be enough unless I also plan to use a deep discharge battery as a starter battery and plan to partially discharge both batteries regularly.)

Now for battery capacity. For this I need to know the typical current draw on a typical day. (Over-specifying will lead to unnecessary battery weight being carried in the vehicle, although it may possibly lead to increased battery life.) Lets assume a typical (working) day is not dark and is not rainy.


Engine on ............... 6.4A
Radio on high ........... 1.8A
Total minimum current ... 8.2A


I don't have a regular commute; I drive out to various local customer addresses during the day, and then to suppliers to pick up parts. I should really have monitored my typical daily driving patterns, but for now I will assume that I spend less than 3 hours driving per day. (Electrical power is consumed purely on a per-hour basis. Mileage is irrelevant in this context.) 3 hours at 8.2A is 24.6Ah. Assuming I will be limiting the donor battery discharge to 50% of its total rated capacity, I would only need a 50Ah battery.

My inuition tells me that 50Ah is not enough, and sure enough I have not taken into account losses through the converter, and then there's all the other little power usages, such as indicators, brake lights, charging mobile phone, use of interior lights, and so on. (All interior lights should be changed for LED's if at all possible!) So what then? 70Ah? 80Ah...?

Arrgh...! But somehow I struggle to accept the use of anything less than 100Ah, despite what I said about adding unnecessary weight. I actually found a source of 110Ah leisure batteries which are low-profile and will not only fit in my spare wheel well, but will also - at a pinch, and with a little battery-tray modification - fit in the engine bay as a starter battery when my current one gives up. They are big enough that, although they are deep discharge batteries with thicker plates, thay actually have a greater CCA rating than my current starter battery. They cost £75 each delivered, and are guaranteed for four years. There is no way one of those will last for four years being 50% discharged every day but that's not my problem and a guarantee is a guarantee. ;) (I guess they reckon that most leisure batteries are only used a few times a year.)

OK, so that's interesting. I was wondering if the 110Ah battery (26kg) would be enough, but it seems it would be more than enough. If I could find a pair of slightly smaller batteries that are of the deep-discharge type and yet are still big enough to start the engine, then that would extend the alternator-free driving time with minimal weight penalty, as I can then safely discharge both batteries to a useful extent. I only need enough power left in the starter battery to start a WARM engine at the end of a day, and on a longer run, when the lights start to dim I just switch on the alternator while driving and all will be well.

I know I said mileage is irrelevent, but just as an exercise, if I drive at my normal 50mph cruising speed, a 110Ah battery should give me 55Ah of power at 50% discharge, which - if I have done the maths right, should give me a dry-road daytime range of six hours or 300 miles before the alternator needs to be switched on. And that's without discharging the starter battery at all. (That doesn't sound quite plausible. I might have to go over those figures again when I'm less tired.)

On a dark, rainy, winter day I might have less than two hours driving time out of this system before the converter cuts out and the main battery starts to discharge.

So, a really long post, and a long testing/calculating session, but I feel the basic specification is done, and it's all looking very feasible.

The next step is to measure actual fuel consumption at various speeds with the alternator switched off. I'll also plug a laptop in with VagCom and see how much fuel is being used at idle with the alternator off.

Then I'll double-check all those my figures, and if they all still add up I'll cost the various options and make some decisions...


[Edit...] Ah, I've just seen a mistake. I think it is probably necessary to have the blower on at least at low speed to prevent the windscreens misting up. I'll experiment with other methods of ventilation but assuming I do need the fan on at speed 1 or speed 2 then that is going to double the current requirement, so a 110Ah battery is NOT an overspecification; it's about right, ...and the maximum alternator-off range is actually looking more like 150 miles, not 300 miles! 150 miles sounds more plausible, and sounds more like the kind of range that others have reported. Still, for daily driving - and most of my driving is daily local driving - I shouldn't need to use the alternator at all with this set-up.

I did a little testing today. With the alternator connected I drove over a 30mph test route of a few miles, both with a 'minimum' current load and with a 'maximum' current load. I noticed quite a marked difference in mpg at 30mph between the two current loads.

At 17.1A (engine and headlights only) I got an average of 93.2mpg (as shown on dash)
At 44.4A (as above + fan at max speed and rear demister) I averaged 79.9mpg.

At a constant 30mph that gives approx 0.5mpg improvement for each amp I can reduce my consumption by, so reducing the current draw from 17.1A to 0.0A should result in a further improvemment of 8.3mpg at a steady 30mph on that route, giving a maximum of 101.5mpg (as shown on the dash display, which is about 7% optimistic.)

Assuming an average current draw of 22A, I calculate that I should expect to save 10.7% on fuel (at 30mph!) by 'deleting' the alternator. Obviously that does not apply to long journies, and also the faster the speed the less impact electrical loads will have per mile, ...though most of my journies are in fact short local journies at low speed.

Soon I shall test with the alternator off. I'm a little nervous of doing much alternator-off testing with my current battery, as athough it appears to be fine, I don't know it's age or its history and I don't want to get stuck somewhere with a dead battery. I'll rig up an alternator ON/OFF switch on the dash so I can switch it back on with the engine running if the battery voltage starts to look low on the meter during a test.

I was thinking today that if I were to get the biggest leisure battery I can fit in my standard battery tray and use that as my starter battery (this happens to be that same 110Ah leisure battery I was going to use in the spare wheel well as an auxilliary battery) then I might be able to use 50% of that battery's capacity (55Ah) before it becomes difficult to start the engine with it. I was thinking that for my normal daily driving pattern that might be enough, and I wouldn't need to use a 2nd battery at all, as long as I was a bit frugal with the amps used. (Once I have the engine pre-heater installed my (winter) days won't be starting with idling on the driveway while scraping off frost, followed by 20 minutes of heavy blower, demister and windscreen wiper use, so amps used will be lower.)

With this 'plan B' one-battery solution I would save all the weight of a 2nd battery, I would save a LOT of complication and I would save a lot of expense too. And if it turns out I need more juice then I can go back to 'plan A' with nothing lost, and with nothing purchased that I wouldn't have purchased for plan A anyway. I can't think of a reason for not 'starting off small' like that, so that's what I'll do. While I'm testing things to see how low I can take the new battery and still start the engine on it I shall carry my current battery in the passenger foot well as a spare.

One downside to the one-battery solution is that I'll be running the car at a lower voltage (Down to 12v instead of 14.5v) and my headlights will be dimmer. I'll try and get some better, brighter, more efficient and possibly slightly 'whiter' headlight bulbs and see if that helps at all. I kind of like seeing where I'm going though. But we'll see...

...Ahh! I've just been reading up on what to do about dim headlights. It seems on the Mk4 Golf all the power to the dipped headlight bulbs goes through the headlight switch, round the houses, back down through the dingly dell and finally on to the headlight bulbs when it's all tired out and a few volts down on what it starts out from the alternator at. I'll try upgrading the circuit with relays close to the headlights and see if that brightens them up enough for me to feel comfortable about running on the lower battery voltage with no alternator and no alternative charging voltage from a DC/DC converter present.

Headlight mod?
 

Having discovered that my mpg rises by almost half a mile per gallon for each amp I reduce my electrical consumption by, I just thought of another mod to reduce electrical consumption.

In most cars I have owned, when the headlight main beam comes on the dipped beam goes off. It's only when pulling on the light control stalk that both come on together momentarily - for signalling.

In my present VW Golf Mk4 TDi (PD) estate car, the dipped headlights stay on all the time the headlight switch is on, even when the high beam (HiD) lights are being used. This uses 110w (or nearly ten amps) that I don't think needs to be used at all. It would be a simple matter to fit a relay in line with the dipped headlight bulbs so that when the high beam is on (2x35=70w) the dipped beam goes off.

Admittedly, I more often use dipped beam than main beam, but it's such a simple and cheap mod, and when I do use main beam it will make about 4mpg improvement to f/e.

Whilst in this vein (and right now this is about extending my driving range without an alternator) I have just ordered some low energy bulbs. So I'll be fitting LED's in place of the regular front side lights and tail lights, as well as rear number plate lights. These are all nominally 5w bulbs at an 80% saving in energy so will save me 40w. (There are two pairs of tail light bulbs.) I also ordered a pair of energy saving H7 headlight bulbs (Phillips Eco Vision) which claim a 20% saving on energy, as well as a doubled lifespan. A guy on t'interweb somewhere has tested the current draw of these and sure enough they put out as much or more light than standard bulbs but use 44w as opposed to the standard 55w. So those should save me another 20w, making a total of 60w saved. I also think it's worth changing all the interior bulbs for LED's, but I'll do that another time.

Frankly, this is small potatoes as far as fuel saved per pound spent goes, but there is the added benefit of vastly improved reliability (and therefore safety) of these low energy bulbs over conventional ones. In the context of designing an alternator-free system, I can expect to save about five amps using these new bulbs, and even more by turning off the dipped beams while the main beams are lit, and that should extend my night-time driving range by about 20%.

I'm so glad I did all that current measurement though as I can now improve fuel efficiency by about 3mpg simply by not using the blower. I was in the habit of using it on speed 2 all the time, which I realise now was using a massive 6.8A. There'll be times I have to use it of course but I've been experimenting with not using it and so far it's been fine almost all the time.

Nearly found my engine pre-heater...
 

Engine pre-heaters are as rare as hen's teeth here in the UK. You can get them but they're really expensive, and there is approximately one manufacturer and one model of heater to choose from. I can get them from the US but they are mostly 110v, and also there can be import tax problems when buying stuff from the US.

But today I found a company in Germany...

AutoteileOst (look for 'motorvorwärmer')

...who sell a range of cheap engine pre-heaters. There is a bit of a language barrier but I think I have found my supplier. UK cars almost never have engine pre-heaters fitted, but I guess winters in Eastern Germany are a bit colder.

Has anyone had any experience with Autoteile Ost?

Subscribed.

Nice thread. I'd point out that Brucepick did something similar--as far as the charging system and "leisure battery"--with his Civic HX before the engine blew. He called it an "externally powered electrical system."
http://ecomodder.com/forum/showthrea...tml#post287705

Subscribed!

I can only recommend replacing the low beams with HIDs. That should save you about 3 Amp on their use (assuming 35W HIDs versus 55W Halogens). And as the HIDs have their own power regulators, a drop in voltage to 12V will have no effect on their brightness.

You would need to use the high beam less often when you have HIDs too. They are about 3 times as bright despite their lower power consumption. You can see the road about 50% further ahead in the dark.

The ecovisions are about 35% more effective than standard. Nice and well.
HIDs are about 400% more effective though. They beat anything, even LEDs and CFLs.

Need to add that my Insight has low beam lenses with produce very little stray light, so at night other road users seemed to overlook it coming from aside (no running lights in European Insights too...!).
My cheap aftermarket HIDs solved that problem, helped by the now very brightly lit area on the road ahead of my car of course.

A good plan RedDevil.

I did look into getting after-market HiD's for the dipped beam lights but balked at the cost. How much did yours cost? If I could get them cheapish then yes, that should negate the need to bump up the voltage to the standard H7 headlight bulbs.

I measured the voltage at the H7 terminals today. At 12.2v battery voltage the headlights were getting 11.0v. With the engine on (and alternator on) the battery voltage was 14.5v and the headlights were getting 13.2v. So upgrading the wiring and fitting a relay would bring the headlight voltage up by at least a volt. With alternator off, the headlights would be getting at least 12v, which should help a lot. And a couple of relays will only cost a couple of quid. But, as you say, HiD's have therir own voltage regulators so they would be much better.

Maybe I should look again at the aftermarket HiD's, but it's costing quite a bit to get the engine pre-heater system and the new battery/charger system sorted out, so the HiD's might have to wait.

...

Hmmm... Just been reading about aftermarket HiD's. It seems they sometimes don't work well in a reflector designed for halogens. It also seems it's an illegal modification in the UK, unless you also have self-levelling headlights or self-levelling suspension, ...which I don't. (Well, LED's as tail lights and side lights - anything except interior lights in fact - are technically illegal too, but they're not as obvious, so you would be very unlucky to be challenged on them. Dipped headlights can potentially dazzle other drivers so will attract more legal attention if they're not standard.

I'm not too keen on spending a lot of money on something that may get me into trouble, and may have to be taken off the vehicle anyway to pass an MoT test. HiD's make perfect sense technically, and congratulations on fitting them successfully on your car, but I think I'll file that under 'to be done later, maybe'. More light, that's true, but only an 18w total power saving over the Phillips Eco Vision (35w per bulb rather than 44w per bulb). If I can't see where I'm going, I do have the HiD main beam lights at my disposal.

Oh, and I just read something about UK law saying that HiD's must be configured so that the dipped beams stay on when the HiD's are on, so it looks like my 'main beam on: dipped beam off' mod would be illegal too. Ah well, like I say, I don't use the main beam that much. (An advantage of driving everywhere slowly!)

Hi Paul.

Google is your friend. I've seen complete HID sets for less that $25 on alibaba.com, yet shied away from that because of delivery time and customs and shipping issues.
Also I do not use PayPal (yet, maybe later).

Several shops over here sell those kits for < 50€; I got me one of those.
It had the wrong plugs, after a hassle with the shop I got the right plugs with a free set of lamps.
They were the wrong color, but still nice as spares. If I ever need them; HIDs typically last for 6000 to 8000 hrs burning time.

Yes, HIDs take a few seconds to get as bright as the halogens they replaced and a few more to get near their full strength. Also you need to clear the lamp units more often; condense does not evaporate and snow does not melt because it hardly emits any heat at all, bright as it may be.

The HIDs draw less power so the voltage drop in the wiring should be less. and the regulating units that come with the set will do the rest. There is no drop in intensity when I key off, despite a 2V drop in voltage.

Over here cars sold with HIDs need beam heigth auto-adjust and automated lamp unit spray cleaners and typically have a double sized window spray tank because of that.
Aftermarket HIDs are exempt from that ruling, as it is almost impossible to retrofit those extra measures on cars that were not designed for it while HIDs do increase visibility.
You need to check your law on that, what makes sense over here might well do so in the UK too.
It might even be one of those European laws bestowed on us.

With HIDs you can choose the color 'temperature'. I chose 5000K which appears chalk white. I already had LEDs for running lights that were 6000K (slightly blueish) that were a big color mismatch with the halogens, but the HIDs look almost right.
I thought the color difference would not matter much, but once you see it it itches.
If I had to do it again I would buy both HIDs and LEDs with a lower temp color (4300K, sunlike white)

Cheers, Bart

Update...

Work has been super-busy lately and I haven't had a chance to do much on this. I've researched various options, and made a few preparatory purchases, but not actually done much. Also, nights are getting longer and I've not had much daylight for working on the car.

I have managed to replace all interior bulbs with LED's. Small potatoes, but just about worthwhile I guess. That cost £25. Well, frankly, if I'd known how much hassle it was going to be I probably wouldn't have bothered. But now it's done I guess it's kind of worthwhile.

I replaced the two front sidelight bulbs with Osram LED's and fitted those Phillips EcoVision H7 dipped headlight bulbs. That saves me 20w. I'll get some LED's for the tail and brake lights, which will save me another 15w. It doesn't sound much but that's probably adding at least 1mpg.

These little electrical savings will save me fuel now and will extend my alternator-free range once I start plugging the car in every night.

I did get a battery to replace my standard starter battery. In the end I went with a 90Ahr AGM battery which was slightly smaller than the 110Ah flooded leisure battery I was originally looking at. The 90Ah AGM is heavier than the original but fits straight into the existing battery box without modification, and it seems AGM batteries are a good choice for this 50% daily discharge regime. It cost £90 delivered and has a four-year warranty. They claim it will be good for 1000 discharge cycles to 50%.

I've just ordered a 10A charger to install in the engine bay and a remote (keyfob activated) relay switch to turn on the engine heater from indoors in the mornings. So the battery charger (and possibly a small, 100w sump heater?) will be active all the time the 230VAC lead is plugged into the car's inlet socket, and the coolant pre-heater (3kw?) will be switched on a half hour before drive-time.


Two further thoughts...

1. Having discovered how much electrical power the heater blower motor uses, I've been experimenting with using windows instead. Once the car is warm I can just about keep the screen clear using the windows, but as the weather has got colder I'm finding I can't heat the car properly without the blower.

I've done some calculations and realised that the blower at lower speeds is incredibly inefficient due to the use of resistors to slow it down (That's Stone Age technology VW!) If I could fit a Pulse Width Modulation speed controller in place of those pesky resistors (resistance is useless!) then I'd save a HUGE amount of power...

At present, the blower motor uses...

Full speed... 217w (including 0w wasted in resistor)
Speed 3/4... 154w (including 46w wasted in resistor)
Speed 2/4... 106w (including 53w wasted in resistor)
Speed 1/4... 75w (including 50w wasted in resistor)

...so on the lowest speed I could cut the power consumption from 76w to about 25w using a PWM controller. In fact, on any speed but the maximum speed (which I almost never use) I would save a similar amount of power: about 50w. That's 4A (!) and will improve gas mileage by almost 2mpg in my car. Given that in the winter I really do need that blower motor, and tend to also use it all year round, this would be a real saving. I can't believe that no one is making after-market PWM modules to replace the resistor pack modules in these cars. (Maybe no one realises just how much fuel is being wasted by these stupid resistors?!) The resistor packs are pretty unreliable too, as they rely for cooling on the motor blowing cold air over them.

(Perhaps an easy, though slightly inelegant solution is to leave the existing set-up as it is and add the PWM in between the blower motor and the max speed contact of the blower speed selector switch, mounting the potentiometer knob of the PWM on the dash somewhere. I can then leave the original switch on the max setting and control the speed with the new potentiometer knob.)

I can't believe VW are forcing me to make this blower motor mod by their continued use of 19th Century technology, but I stand to make more gains by doing this than by all the lightbulb LED replacements combined. A blower motor PWM controller should save me about 50w under nearly all driving conditions, whereas the LED's will only be saving me fuel when it's dark.


2. Now what was that other thought...? Oh yes, a slight problem. If I drive with the alternator field wire (IGnition wire) disconnected from the alternator, then after about ten minutes a warning light comes on. It's actually the 'ESP' warning light (yellow triangle) that normally indicates that I have switched off traction control, but reading up on it reveals that it will also come on if there is a break in the field wire from the ignition switch.

I haven't tried yet but I think I can stop that warning light coming on if I connect a 12v +ve supply to the disconnected Ignition wire so the ECU sees a proper voltage on that wire and 'assumes' the alternator is working and is supplying '12v' to its own rotor field. I'll experiment, but I don't like having warning lights on the dash, even if I know they don't mean anything. I guess if the experiment 'works' then my alternator ON/OFF switch will have to be a changeover switch that disconnects the IGnition wire from the alternator field and connects it to a 12v +ve supply.

(I'd thought about including an 'alternator kill switch' which drains the field current down to ground in an already excited alternator, but it's also very easy to momentarily stop the engine if I ever need to kill the alternator while driving, so I won't bother with that one.)

So that's the update. Mostly thoughts rather than actions, but it's all coming together gradually.

how did you calculate the watts wasted at the resistor? because my car also use a resistor to control the speed of the blower motor.

echofrancis, I had already measured the current used by the blower motor at different speeds. (There's a post in this thread with all that data laid out.) I then simply applied Ohm's Law to work out the rest.

In my case (VW Mk4 Golf) that works out like this...

Current draw of blower motor...

Speed 4/4... 17.5A
Speed 3/4... 12.4A
Speed 2/4.... 8.5A
Speed 1/4.... 6.0A

At full speed (4/4) there is no resistor in series so I can calculate the equivalent resistance of the blower motor from Ohm's Law (R=V/I) 12.4V / 17.5A = 0.7ohms.

So then for a 6.0A current passing, there would be a 4.2v drop across that 0.7ohm 'resistor' (Ohm's Law again: V=IR). Therefore the remainder (8.4v) of the total 12.4v is seen across the resistor, and at 6.0A that is 6.0A x 8.4v = 53.76w dissipated (wasted) by the resistor and only 25.2w used by the blower.

There are other ways of calculating but it's basically Ohm's Law.

I find it quite shocking how much energy I'm wasting by having the blower on all the time, and yet, in the winter especially, I can't do without it, so that's a constant 50w being totally wasted whether at night or in daylight.

Now I'm trying to maximise mpg and I've measured the difference in mpg (at 30mpg) at different levels of electrical load. At that speed I'm getting around 90mpg (Imperial) and the difference made by using an extra 1A of electrical power is just under 0.5mpg at 30mph. So that 50w, being equivalent to roughly 4A, is robbing me of just under 2mpg. Your mileage may vary, but the absolute amount of fuel wasted by having 4A of unnecessary electrical load is going to be about the same no matter what vehicle you have. (Well, an efficient diesel will waste about the same as mine and a less effiecient petrol engine will waste much more to produce those 4A.)

(I can't believe car manufacturers still use this old technology. Well, I guess it took them long enough to start using LED's. I well remember cursing them for using tiny incandescant light bulbs in the dash illumination when I had to take the whole dash apart to change a blown bulb (!) This was years ago but LED illumination was already well-established technology for low level lighting. LED's would have been so so easy to incorporate onto the instrument circuit board and would have lasted for the life of the vehicle.)

So, the short answer is, I just used standard Ohm's Law. But I would never have known how much was being wasted there if I hadn't measured the actual current being used on my car. I really recommend doing that. Borrow a DC clamp meter if you haven't got one. That makes it really easy, and you only have to do the measurement once. Once you know what each item of equipment is using you can refer to the list and you'll know how many amps you're using depending on what equipment you have on at any one time.

Oh, and by the way, I've been calculating and measuring based on 12.5v, because I'm planning to drive around without the alternator, but if your alternator is running and producing 14.5v then the power being wasted will be even higher.

And just for the record, I know I measured the effect on mpg of electrical load with the alternator running (of course!) so the voltage will have been 14.4v and not 12.4v. That will skew the figures a bit.

I just did the calculation and my resistor dissipate about 25-26w of power:(
does a PWM controller look like this HOSSEN® NEW 6V-90V 15A DC Motor Pump Speed Controller: Amazon.com: Industrial & Scientific ?

26w wastage isn't too bad. That's less than half of what mine wastes. What wattage is your motor at full speed?

At 12.4v mine wastes around 50w (50w, 53w or 46w) at all speeds apart from full speed. (At 14.4v it wastes 66w, 74w or 62w at speeds 1, 2 and 3 respectively.)

To be honest, I don't really know what these PWM's look like. I only know what I've read online myself. I think the one you linked to is probably the kind of thing to use. PWM motor controllers I've seen online look similar and cost a similar amount. However, a 15A rating would not be enough for my blower motor, and even if yours is significantly smaller I still don't think a 15A rating would be enough. Motors can sometimes take a surge of power when they first start which is much higher than their sustained current draw. This isn't normally an issue with simple resistors, as they would take a while to overheat anyway, but I think you'd need to over-specify an electronic controller by quite a wide margin to avoid problems. In theory, a nice big capacitor across the windings of the motor would supply the start-up current boost required but it's better to get a controller you are sure is big enough to start with. But I don't really know any of this from first hand experience. Maybe these controllers have large enough output capacitors built in to them anyway. Doesn't look like, but maybe.

One thing (as far as I have read) that you need to be aware of is the frequency at which the PWM switches. If that frequency is within the audio range then the motor can end up audibly humming. 20+KHz should apparently be OK unless you've got ears like a bat. ;-)

But do your own research and don't rely on what I say. I've only recently looked into these things since I realised how much power those resistors are wasting.

If you fit a PWM before I do let us know how well it works.

my blower motor use
1, 39w
2, 55.5w
3, 98w
4, 146w 11.7a
I like the PWM idea because I allways use my heater at speed 1 or 2
and at those speeds 50%or more of the watts are wasted.

I'm looking at this one...

12V 30A 360W DC Motor Speed Controller with Enclosure | eBay

...more expensive but it ticks all the right boxes for me. Right current rating, right frequency (ultrasonic), comes with a case and can be controlled using a simple 0-5v signal, which can be fed directly from the existing speed selector switch (with judicious addition of a few voltage-dropping diodes) without running any new wiring or requiring the addition of an extra control knob on the dash. Also, the listing shows that the seller understands what he's selling.

But your blower motor is almost exactly half the power of mine so maybe you don't need such a high-rated controller. The lower-powered ones are MUCH easier to get hold of. Also, if you wire it up clever then for the highest speed the current doesn't have to go through the controller at all but can bypass it. That way, the maximum current you put through the controller is going to be for your second-highest blower speed, whatever you decide that will be.

It is entirely permissible to rig it so that the three controlled speeds are slower than the existing three controlled speeds and then there's a jump up to the maximum, uncontrolled speed. That way, the maximum current you ever put through the controller need only be about 5A. (Or for me, 10A.) I myself very rarely use speed 3/4. I sometimes use speed 1/4 but mostly use speed 2/4 for everyday use, ...and then very occasionally, when I need all the power I can get for a brief period, I'll use speed 4/4. I'd probably be happy with just two speeds but that would make the speed selector a bit weird. Just thinking aloud here but in fact I could use a much lower-rated controller (say 15A, which is readily available in the UK) and have in effect, speed 1, 1.5, 2.5 and 4.

...

Aha...!

http://www.amazon.co.uk/6V-90V-Pulse...pr_product_top

...only 15kHz, so not strictly ultrasonic, but I personally can no longer hear 15kHz at all (snif) so it should be OK. One of the Amazon reviewers there had good luck using this unit to control the blower motor on his Landrover so I have a good chance of success with it. I do like the fact I can control the output with a 0-5v signal rather than having to use a potentiometer.

By the way echo-francis, I just noticed what mpg you're getting there. Impressive. In theory you should be able to squeeze a couple more mpg out with the blower motor PWM mod.

Another test I can recommend is to measure mpg at various electrical load levels. (Do you have a real-time mpg meter of some kind in the car?) That will give an idea of the mpg gains you get by reducing the load on the alternator. I would imagine that a small, petrol-driven car (?) which already gets high mpg would get the most mpg gains from reducing electrical load because the alternator is using a higher proportion of the engine's output. Also because petrol engines tend to be less efficient than diesels in absolute terms of power produced per gramme of fuel burned, so all that electrical power is going to cost more fuel than in a diesel.

...

Ha ha - i just found your thread. Loads of good stuff there. I'll be back for a good long read soon. Also I just realised the 'perfect' PWM I just found is the exact same one you found. Looks good to me.

Quick update. Workload has prevented me from doing much. I've replaced the last few light bulbs with LED's, but not much else... (I had trouble with the combined stop/tail bulbs and had to modify them to get them to work.)

...but I have finally at least purchased all the kit I need for this alternator delete mod. A 2KW Kenlowe engine coolant pre-heater kit and a CTEK 10A temperature compensated battery charger. Now i just have to find the time - and a gap in the weather! - to install it all. I might crack and get my mechanic to do it for me, ...at least to install the heater and pump into the coolant system. That part will probably have to be done from below, and I'm not keen on crawling around under cars outdoors in this cold wet weather.

I also bought a PWM motor speed controller to fit to the blower motor, but it looks like that's not as straightforward as I thought it would be. It turns out the first controller I bought (from China) does not use a common negative for input and output (it uses a common positive) so I can't just ground the negatives of the input and the output. It can still be done, but it will need a bit more thought. I have bought another one which might be easier to install. Anyway, I think I'll put that one on hold and concentrate on the alternator delete and pre-heater for now...

But yeah, looking forward to having a slightly hybridised car in a little while! And one that starts each morning at 80 degrees Celcius!

One comment on the blower motor speed control. While the OEM uses discrete speeds for the blower motor, with a PWM controller there's little reason to keep that. The fan speed can be varied continuously if you contrive a variable input.

Agreed Occasionally6, ...in fact these PWM's come with potentiometers and control knobs, so that's probably the easiest way to use them: just mount the supplied control knob and pot' on the dash, extending the wires if necessary. I would want to be careful not to run so low a voltage to the motor that it won't turn though - in case that damages the motor. I'd probably want a 'bypass' resistor for the lowest speed.

Actually I prefer, when driving, to have a tactile indication of what level I've set things to. I kind of know, under given driving conditions and at a given vehicle speed, that blower speed 1 will be enough, or that I'll need blower speed 3 for a while and then can drop down to blower speed 2 once the windscreen is clear for example. I also quite like the idea of not having an extra control knob on the dash if it's not needed. Ideally, I'd have four trimmer potentiometers back in the guts of the wiring connected to the PWM and switch between them using the stock VW control switch on the dash. That way I could infinitely adjust each blower speed to my own requirements and then when I have them right, leave them alone and use the stock control switch.

But I'm not clear about how these things work. (E.g. why do potentiometers need three wires?) I know some of these PWM's can have a 'control voltage' input between two contacts (0v - 5v for some PWM's) to control the output power voltage, but I don't know if the one I bought can accept that. (I guess I should ask the guy in China I bought it from.) That would make life really easy as I could then simply solder resistors between the output terminals of the stock VW speed selector switch.

But that's for another time. I've been puzzling over the installation instructions of this Kenlowe coolant pre-heater, trying to decide where it will fit best in my engine bay. The unit looks well designed and well made.

Update: (it's been a while...)
 

It's been a busy winter so far - and a really, really, record-breakingly wet winter. The wettest January in the UK since records began 250 years ago. It has rained virtually every day and I have not felt like working under a car on my driveway, so all this was put on hold. Also, during one of the many storms we have had a tile fell off my roof onto my driveway so have not felt too comfortable about parking my car there by the house where I can plug it in to the mains power supply, in case another tile falls on it.

However, I did manage to fit a waterproof outdoor power socket on the wall of my house by my driveway, and also, crucially, I got around to getting rid of an old van that had been permanently parked on that driveway for the past 5 years and had been used as a storage shed. So now I have a space to park the car and a means of plugging it in to the mains overnight.

I still haven't got that engine pre-heater installed, but today I did fit the battery charger in the engine bay and sorted out a temporary way of plugging it in overnight. I disconnected the alternator field wire, so from tomorrow onwards I shall be running without the alternator for all normal daily driving, only switching the alternator back on for longer trips of more than about 150 miles.

I'm kind of regretting buying that expensive and rather complicated coolant heater. Monitoring more closely the mpg meter in the car, it seems the mpg is only significantly higher for the first few minutes of driving, and yet it takes nearly 30 minutes to get the engine up to full temperature in the winter. After 5 minutes the engine temperature is probably less than 50 degrees. My guess is that a simple, cheap, silent and reliable oil sump contact heater, of the self-adhesive type, and of perhaps 125 watts power, would be enough to warm the engine to a point where the fuel economy is reasonable from the time the engine is started. I would need to switch it on a few hours before drive-time, but at only 125w I could probably justify leaving it on all night along with the battery charger. I have a 100% grille block and a good engine undertray, so the engine would probably stay fairly warm even with a mild breeze blowing. I could also insulate the oil sump with PU spray-on foam, which would increase the effectiveness of the heater, and would also help to keep the oil warm for longer when the car is parked up away from home during the day.

So, I'm not sure what, if anything, I shall be doing about the pre-heater in the short-term, but I am looking forward to seeing what gains I get now with the alternator switched off.

..and the pre-heater...
 

OK, so I'm in the process of installing an engine preheater which I bought back in October/November when the MET Office were predicting a long, cold winter. In fact we've had a rather warm and extremely wet winter and i haven't got around to installing the heater unit until now.

It's a 2Kw Kenlowe coolant heater and pump that is supposed to heat the engine to 85 degrees Centigrade.

I've got as far as plumbing the thing in to the heater hose and now I'm struggling with the electrics. Currently struggling to install the mains connector on the front grille without it sticking out forwards in a potentially pedestrian-injuring way.

It has taken MANY HOURS to install this heater thing but I'm getting there. And I am enjoying the process.

By the way, my initial impressions on running without using the alternator are encouraging. So far on my daily driving routes for work and social use, I have had no cause to worry about the voltage getting too low. It starts about 12.5 under load and it seems I can take it down to 11.5 under load with no problem at all. That represents about 4 or 5 hours driving with no lights or windscreen wipers, etc, or about 2 hours with all that stuff on. My overall running mpg average seems to be up by about 10% and the test runs I've done show that indicated mpg at 30mph is up from about 87mpg to 99.9mpg. (The gauge only goes up to 99.9mpg). 50mph test runs show a somewhat smaller inprovement of about 5%.

I have a CTEK waterproof, temperature compensated 10A intelligent charger sitting in the engine bay, connected up to the 90Ahr AGM battery, and I plug that in to the mains when I park up on my driveway. I have a 4-digit illuminated volt meter mounted on the dash that I can also read through the rear window if I'm not in the car, so I can get an idea of the state of charge while it's plugged in. The 10A charger seems to fully charge the battery overnight with no problem at all, although I haven't got in there with a current meter to confirm that.

More later...

I would be interested in seeing a pic or two of how you have it all arranged in the engine bay... charger & battery & coolant heater with pump.

Would you be able to do a timer on the coolant heater, so that it switches on automatically 2 hours (or whatever) before you have to leave?

Just read the whole thread, you sure type a lot of words paul ;-)

I'm basically doing the same thing myself, except I'm working with a van with a roof covered in solar panels. 400w of panels cost about $1000 on ebay. So far I have a 30A MPPT controller, but only a single 40w panel for testing purposes.

For the headlights, why not add the voltage regulator just before the headlights? That way you can run a single battery but still have 14.5 to the headlights at all times.

As to PWM vs resistor fan controller, OEM's have been using PWM since the late 80's but you have to buy a model with Climate Control to get it. I just bought a 10A unit to experiment with. It will run my DRL's, but I'll try it on the fan first. I plan on adapting the potentiometer to take place of the OEM switch. The adjustable preset speeds idea is a good one though, but I figure there'll always be a point where the desired speed is in between two settings.

Great work on taking measurements and sharing your results!

I'm still a fan of the HID retrofit. Sure, it can cost a bit to buy a quality kit that includes a proper projector or reflector, but it will consume significantly less power and resolve the voltage sag issue. If you buy something in the 4000K range, the color should be subtle enough to not draw attention of motorists or the police.

The kits are not permanent, so you can return the car to stock form and move the HID kit to your next car when the time comes.

Nachritter, yes, I will take some photos soon. This weekend I should have time during daylight hours. I notice you have a 2000 VW Jetta. Is that what VW Golf's are called in the States? Yes, sure, watch this space: pictures will be forthcoming. I should complete the installation this weekend, if not before.

The battery charger part was dead easy. The charger is a CTEK MXS 10.

CTEK MXS 10 Car Battery Charger - the smartest battery chargers in the world!

I got the most powerful charger available that was reasonably waterproof (and that means without a fan of course!) so only 10A. It seems to work well. Also this charger has a temperature sensor, and a specific AGM setting, so no risk of undercharging in winter or overcharging in the summer if I park in the sun.

As for the timer, well a timer would be great if I had a 9-5 job and drove off at the same time every day. But I don't, so I got a little radio-controlled relay and key fob remote activator. The plan is to fit that inline with the coolant heater, so when the mains lead is plugged in the battery is always on charge and I can activate the coolant heater from my bed ;-) or a half-hour or so before driving off.

If you have more regular daily habits than I do then a timer would be ideal, but if I were doing this again I would look at getting an even simpler self adhesive oil sump heater pad (from Wolverine or similar?) and wiring that up together with the battery charger so it is on all the time. Much, MUCH easier to install and less to go wrong. 100w or 125w should be about right, depending on your local climate.

Thanks Redpoint. Using after-market HiD's for the dipped headlights WOULD solve a few problems at once - you're right - and it is an elegant solution in that regard. (No headlight dimming without the alternator, and less power consumed.) However when I looked into it I found it wasn't that straightforward for my car, ...mostly for legal reasons but also for technical/cost reasons. But I will look at it again another time.

[EDIT: I think I decided to try first upping the headlight voltage by running power to them direct from the battery via a pair of relays. The stock wiring is rather thin and goes the long way round via the headlight switch on the dash. Fitting those relays would be cheap (£10?), easy, legal, and would increase voltage by at least a volt, so when my battery is low (11.5v) the lights will be as bright as they are now when the battery is fully charged (12.5v). At 12.5v the lights are definitely bright enough, at 11.5v they are only just OK, but when the battery gets really low (11v?) the headlights do dim alarmingly and that's what compels me to stop and reconnect the alternator. The engine will still start at 11v, and everything else seems to work fine, so fitting the relays should increase my night-time alternator-free driving range by a margin. I'll do that first and see how it goes.]

I tend to use headlights only when necessary, and having good, strong, LED sidelights means I often can get away with just using those. Around town at night I will typically use sidelights only (all LED's on my car) and only switch headlights on when approaching a junction. (Sidelights-only-running is legal in street-lit areas at night in UK.)

Photos would be great; thank you.

Generally, the Golf is also known as the Golf here in the U.S. However, the Jetta estate that we received in the U.S. is essentially the same as your Golf estate; only the body cladding is different. We did not get the Golf estate. The Jetta I have is a saloon/sedan.

Of course, the engine compartment is identical, so being able to see how you installed the various components would be interesting.

I get what you mean about the timer; it would not be very useful for me for the same reason you state. The remote is a nice idea.

Oldtamiyaphile, thanks for the idea of putting a step-up voltage regulator unit before the headlights to keep the voltage constant there. I hadn't thought of that. It wouldn't even need to be a sophisticated unit. I could even use one (or two?) of those cheap in-car laptop chargers that output 15v.

[EDIT: ...but I'll try the simple and cheap option of fitting a pair of relays first so I can feed the headlights from a pair of short, thick cables with inline fuses direct from the battery. That will give the headlights an extra volt, which may be all I need.]

As for the PWM controller idea, that 10A PWM unit should be suitable for the heater blower but you might need to bypass it with a switch for the highest speed. At 12.5v my blower motor takes about 16A at full speed, 8A at speed 3, 4A at speed 2 and 2A at speed 1, and at 14.5v those motor loads will be proportionately higher of course, so 19A at full speed and 9.5A at speed 3. I got a 15A PWM so I would have to do the same thing and bypass it for speed 4.

(Frustratingly, I also bought a 30A PWM from China but then discovered it has a common positive rather than a common negative, so not good for use in a car with negative earth! My mistake: I should have asked before buying it. The 15A one should be fine.)

...but why are you using a PWM for controlling DRL's? Are the DRL's on your car just the headlights fed via a resistor?

Engine pre-heater is up and running!
 

I completed the installation of my 2kw coolant heater/pump today, and tried it out this evening. (Woo-hoo!)

I had not driven the car all day so it was stone cold. Ambient temperature was about 9 degrees. (All temperatures mentioned here will be in Centigrade!)

The coolant heater took 20 minutes to heat the coolant to 50 degrees, and a further 50 minutes to heat it to 88 degrees, at which point the thermostat shut off the element and the pump continued to run on its own until the temperature dropped to 78 degrees, then the element switched back on and temperature rose to 88 again. At that (rather high) ambient temperature the 1.8kw heating element was on for about 30% of the time to maintain the 78-88 degree coolant temperature..

I left it to cycle a few times as I was busy doing something else indoors. I finally got in and did a test drive after the heater had been on for about two hours.

I should say that most of my daily driving is on short, local journies of less than 10 miles at low speed, although I may drive 50 or 80 miles total in a day on my way to customers' houses or to suppliers, or to social events etc. in the evening. The engine barely has time to warm up on short drives like that. I live about 5 miles from Oxford and I've often noticed that if I drive into town (with a cold engine) the in-dash mpg display will show an average of maybe 85mpg, but on the way back home - even if the car has been parked up and cooling down for an hour or so - I'll get closer to 100mpg displayed. (The dash average mpg display only shows up to 99.9mpg in fact.) I was never quite sure whether this difference was to do with temperature, or whether it was more that on my way into town I am sometimes in a rush but on my way home I may be driving more sedately. It may be a bit of both, but still 'n' all, I have NEVER got better than about 85mpg on that run into town on a cold engine (much less than that before I stopped using the alternator!) and tonight I got a solid 99.9mpg displayed on the dash both ways.

So, a success I think!

It probably helps a lot that I am not doing all that reversing and manouvering to get off my driveway on a stone cold engine.

I've deliberately not yet tried to install the radio controlled switch for switching the pre-heater on from inside the house. I fitted a manual switch under the bonnet for the time being, just to test out the heater unit before introducing any potentially confusing radio-related variables. Assuming the heater continues to work as expected, I'll try fitting the remote switch thing in a week or so.

One other thing I noticed this evening while the coolant heater was running is that if I try to use the blower to heat the cabin (I would want to use it to defrost the windscreens if it were colder) then the coolant temperature is dragged right down to 58 degrees. That's only 50 degrees above ambient, so at -10 ambient, if I were trying to use the blower to defrost the screens, the coolant temperature could be dragged down to 38 degrees! It turns out that 2kw is not that much after all!

However, I realised that it would be quite easy to fit a power socket and a 230v fan heater in the front passenger foot well. The socket would become live when the coolant heater/pump is switched on. A 1kw heater would be about right, and I happen to have just such a heater lying around somewhere. (Well, it's a 2kw heater but it also has a 1kw setting and I can easily rewire it so the higher setting is disabled. I am limited to about 3kw, or 13A@230v, as that's the most you can run off a normal UK mains plug and socket.) I would only need to use the fan heater if the temperature were below zero (Centigrade!) but using that instead of the car's blower motor would allow the coolant heater to do its job properly and get the engine up to full heat.

So yes, a success I think!

Oh, and I was concerned that the pump might be noisy, but it isn't. It can be heard as a humming inside the car, but from outside it can't be heard with the bonnet closed.

But now I have a problem. My car's dash display only shows a trip average of up to 99.9mpg. I'm regularly exceeding that since I stopped using the alternator, and as the weather warms up that will go even higher. I think I can change my car's display (using VAGCOM on a laptop?) to show litres/100km instead of mpg, and I can't see there would be any such display limit in that case, as the figure would be going down with better efficiency rather than up. I may have to do that soon!

Been following your progress for a while and have thaught about doing the coolant heater mod but decided agains for a few reasons, one being the cost of mains electricity. Have you done the maths and factored this in?

Hi fearone,

To be honest, no I haven't done the maths on the coolant heater re cost of mains electricity used vs cost of diesel saved. My guess is that there's not much money saving available there. Also, I don't yet know how much fuel I'm saving by starting off with a pre-heated engine. (10% over the first ten miles?) I suspect that there is a 'sweet spot' whereby if I heat the engine quickly to a medium temperature like 50 degrees, I will avoid the really bad fuel economy of a stone cold engine without using too much electricity.

I also haven't costed out the battery charger vs alternator thing, but I am totally convinced that the mains electricity used to charge the battery is a lot cheaper than charging it using diesel. I'm saving about 10% overall on diesel through the overnight battery charger mod, and over a year that's at least £150 for me. Recharging the battery uses only about half a kwHr overnight, or less than 200 KwHr per year. At a generous 20p/kwHr, that would cost just £40 a year, or 10p a day. (And that's an absolute maximum cost, assuming I take the battery down to 50% charge every single day, which I don't by any means.)

[It's also possible to put the charger circuit on a timer so it uses only cheap, night-time electricity. (I'm on an Economy 7 tariff.) In my case that would just mean a timer that doesn't allow power through to the external socket before 11pm, as by morning the charger will have cut its output right down to a trickle anyway.]

Once the battery is fully charged, leaving it plugged in on trickle charge uses almost no power, whereas a warm engine is constantly cooling down, and the warmer the engine, the faster it will cool down, so a short, sharp burst of heat just before drive-off time is the thing to aim for as far as economy goes. I found yesterday that 20 minutes at 1.8kw heated my engine by 40 degrees from 10 degrees (Centigrade) to 50 degrees, but it took a further 50 minutes at 1.8kw to raise the temperature by the next 38 degrees to 88 degrees. It's really difficult to know, as engine temperatures keep rising as I drive, but my feeling is that the really bad mpg happens below 50 degrees C. 20 minutes at 1.8kw costs about 6p, but heating the engine fully would cost an additional 15p.) 6p buys about 30g of diesel or 0.04 litres. Hmmm... I reckon it's roughly 'cost neutral' in terms of fuel as long as I don't keep the heater on for more than 30 minutes or so. But in a vehicle which is less fuel efficient than mine, the saving would be that much greater.

The coolant heater mod was a brave experiment for me. It does improve mpg, but it was expensive and complicated to fit. I could not have justified it to myself on fuel-saving grounds alone, but it will also contribute to safety, save wear on the engine, save me time and trouble on icy mornings, reduce the polution the car produces and will mean I don't have to idle the engine on my driveway, annoying the neighbours and poisoning their children.

I would definitely, definitely recommend the alternator delete mod though. Real cash money to be saved there.

Photos...
 

OK, photos. Lets hope this works.

(Sorry about the large photo files. Next time I do this I'll resize them to save bandwidth.)

Overview...

http://www.gato.co.uk/private/car_ph...8_18.10.44.jpg