Alternator bypass & engine preheater mod

[oldtamiyaphile]

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.

[redpoint5]

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.

[paulgato]

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.

[paulgato]

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.)

[NachtRitter]

Originally Posted by paulgato

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.

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.

[paulgato]

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?

[paulgato]

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!

[fearone]

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?

[paulgato]

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.

[paulgato]

OK, photos. Lets hope this works.

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

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