Alternator modifications
 

I found a paper on improving alternator efficiency. With out a whole lot of work one could bump there car alternator efficiency by 4%.

http://itee.uq.edu.au/~aupec/aupec04.../PaperID82.pdf

I'm also wondering about replacing the diodes in the alternator with ones that have a lower voltage drop.

Downloaded for reading. Looks interesting.

Save time; Disconnect Alternator And Run On Battery
 

Some of you may remember me, I have always been a supporter of the idea of just disconnecting your alternator to increase MPG.

I did this on:
2004 4.7L Dodge Dakota
2004 Jeep TJ
2009 Honda Accord

I had no problems and was able to drive 75 miles before reaching 12.1 volts on the stock battery.

Today, I have a Group 24 Gel Cel in the trunk of my Honda and a quick alternator disconnect that can be used to turn off the alternator and go for about 50 miles in the summer heat without any worries.:thumbup:

...or you could slow down by 1 MPH and probably get just as much benefit!

Hyundai i10 "Blue" model in the UK has an "Alternator Management System" which seems to monitor when the engine is under load (e.g. climbing hills, accelerating hard) and reduces the demand from the Alternator from the engine. It also increases it when it can such as in gear downhill coasting etc.

Linky

Here is a pic from the brochure

http://ecomodder.com/forum/member-ar...alternator.jpg

The "Blue" (named after the VW/Merc "Blue" eco technology - well they don't want to give the Green Party any credit do they ?) failed for me because it's too expensive for what it is.

The engine being under higher load can demand more from the electrical system -- but I could be thinking in terms of points and condensor ignition. Changes in voltage can result in a weaker spark, which is the last thing you'd want.

Another mod that could be worthwhile (for those of us who love our forced-air HVAC) would be to replace the blower motor with something more efficient, or to lighten the fan blade assembly to reduce the torque needed to turn it. Maybe even to add an ultra-low speed to the blower motor so the A/C can be run with minimum blower electrical load. Most A/C will not engage the compressor if the fan isn't running, so to have a fractional amperage fan setting, or even an override if you're in the "Fresh" mode so that the A/C will run with the fan off, can save some electrical demand.

Tie the fan speed automatically dropping under high engine load with the alternator cutting out under the same conditions, so that you're not burdening the battery so much up those hills, and downhill, the battery recharges just that much faster.

What about one of those "flexable" solar panels on the roof to keep the battery charged?

Another interesting paper showing typical losses for each part of the alternator as well as potential savings of improving alternator efficiency.

http://www.delcoremy.com/Documents/H...ite-Paper.aspx

In it they say that the two leading losses of efficiency of an alternator are the Ohmic loss of the wire and the diode voltage drop.

On the Honda do you really gain much as Honda uses a 2 stage load alternator , ELD (runs at low outputs with low loads to increase mpg ) ?

An alternative (no pun intended) is to carry a battery with slightly higher nominal voltage than the car:

http://ecomodder.com/forum/attachmen...1&d=1303633944

I'm getting a 5A boost at the beginning of a trip and then it goes down towards 2A in an hour.

At least you have more than 2 distinctly different parties :/

___

I really want to try this mod on Teggy -- I have a switch for the transmission/TC, why not for the alternator as well?

My biggest concern is the extended time the vehicle remains parked up to a week or 2 outdoors -- is there a minimum recommended voltage on a stock batt? I'm sure after time, it can really wear on an average battery -- any thoughts there???

-RH77

We have at least 4 large ones in Scotland - be careful what you wish for, the choice and variety is no better...

I have been "planning" on this idea for a while. My 98 Civic has a roof large enough for a 120w panel that would generate 18v at peak (I'm still learning). I want to install an alternator kill switch and LED lights as well. I think I could run the car possibly all day with the alternator off, and then turn it on as the sun weakens. One thing would be great... my extended EOC usage would not kill my battery because the panel would still be recharging even though the engine was off.

@rgathright: those batteries are heavier than stock, no? I was hoping for a lighter deep cycle battery to contribute to my weight-reduction program too.

What % of total engine load is alternator?
 

rgathright,
What percentage increase in mileage do you get with the alternator off?
Do you re-engage the alternator when braking or coasting down a hill?
Did you replace your starter battery with a deep cycle battery which is built to not expect immediate recharge?
If you replaced you battery, how has it effected your cold weather starting?

CatbusMike

...connecting the brakelights to electronically "re-engage" the alternator field would cause charging only when decelerating.

...simply replace the "hot" (+12VDC) line going to the regulator device/module with a wire connected to the brakelights = field engergized only during breaking.

My idea for an alternator modification is to replace the shaft pulley with an Air Con-type clutch/pulley. With a circuit sensing batter voltage, while the voltage is adequate, the clutch would allow the pulley on the alternator to spin freely. When the voltage reaches a pre-determined low, the clutch would kick in, turn the alternator and recharge the battery. You'd only spin the alternator when you needed to on long trips, and could top the battery at home via a trickle charger between trips.

This could work on stop-start urban trips, but would be problematic on long journeys with little stopping.

another paper

Automotive Power Generation and Control

The alternator on my car will continue to charge, once the field is energized, until the engine stops and power is removed from the field. As I don't know if this is damageing in some way, I leave the switch on until my next EO(ff)C. I monitor my battery voltage and tend to leave the alternator on when in stop and go traffic. If on a longish trip, I engage the alternator when my battery voltage gets to 12.0vdc at rest( seems to stay around 12.2 for quite a while). I do charge my battery at night, except when thunder showers are going on). I also turn the alternator on (and injectors off) when engine braking.

JethroBodine,

Deep discharging a battery like that for prolonged periods will shorten its life. Keeping your battery voltage up near 14V will help keep the plates from sulfating.

Old battery, came with the car. Using it a test subject for use and abuse. I am going to get a deep cycle before winter. I carry jump pacs with me for emergencies.

I propose to move the discussion about alternator killing to one of the many related threads (for example: Automatic alternator cut out/regen braking), and use this thread only to post relevant info on increasing an alt's efficiency, as was the OP's intention.

Second the proposal. Same should apply to solar augmentation too.

My sense of this alternator mod is that it might not add much because an alternator that is not "on" spins fairly freely anyway, no?

I really like that modified bridge (figure 8.e). I played around extensively with controlling DC motors using PWM in college, but I never gave any thought to doing the same for an alternator.

Then how could someone who deletes an alternator see up to 10% mpg gain, as reported here?
A battery in normal use would be charged to replace the investment made in starting the car in a few minutes. You wouldn't see 10% mileage gain from that.

Brian

Yup. That's a good question. I think the folks with the 10% gains were running the batteries down and then charging them through plugins, trickle chargers, and solar panels. The gain then might not be so much from taking the belt off as from not putting it back on to charge the battery and thus add that load to the engine. Take another look at MetroMPG's test: http://ecomodder.com/forum/showthrea...8.html#post958. He tested with a disconnected belt without including recharging load. If somebody with an alternator kill switch wanted to test the difference between belt on (alternator off) and belt off and report the results, that would be one way to answer this, maybe. Or maybe someone can answer what sort of load an "off" alternator is really putting on an engine. I don't know.

I think this "10%" improvement is kind of misleading, given that MetroMPG started off with a FE of 71.2 MPG (or 3.3 L/100km).

I ran the numbers, and found that he saw a reduction in fuel consumption of 0.3 L/100km. Given his starting consumption of 3.3 L/100km, that is indeed a 10% improvement.

However, if I were to apply this same fuel consumption decrease to my own FE (last tankful was 20.5 MPG or 11.5 L/100km), I would find that I would only see a 3% improvement in fuel consumption.

Alternators do not take that much energy to spin. Noticeable, yes. However, will somebody currently seeing 25-30 MPG see a 10% improvement if they disconnected their alternator? Nope.

It's not to say that one should not look at improving the efficiency of the alternator (or removing it in favor of some other form of battery charging). For instance, if I again use my truck's performance as an example, I would find that I would pay roughly $2.65 per fillup for using my alternator. I would love to cut that figure down.

I'm only saying that one should not expect vast improvements from alternator modifications/deletions. Probably not a really good idea to utilize percentages when talking about FE improvements, either (at least if one is considering modifications that do not change the dimensionless coefficient C(d) ) . Heck, for that matter, it'd probably be better to talk about FE in terms of L/100km rather than MPG.

t vago,

I agree. I think we could quantify a percentage in the power required to spin the alternator to generate a given amount of electricity that the engine must produce. I have seen figures of 1HP per every 30A assuming a 55% efficiency of the alternator.

Watts / 745.7 (one HP) = Electrical HP Produced by the Alternator

30A X 14.0 = 420 W

420/ 745.7 = 0.563 HP electrical power

HP electrical power/ efficiency = HP mechanical


0.563 / 0.55 = 1.0236 HP mechanical

In the paper you listed, they showed a 4%increase in efficiency(at 14vdc output) by using a constant 4amp field excitation voltage. They did not generate the excitation voltage from the alternator, but from a seperate power source
. How much power does it take to generate a constant 4amps? The standard alternator set up in their test used up to 50 watts of its own output(variable draw). If it were 50watts, just to make things equal between the two modes, wouldn't that draw a higher percentage of the alternators output at lower engine speeds and/or alternator outputs?

Why not just downsize ?

This may have already been covered or maybe is irrelevant so apologies in advance, I work in IT so I haven't followed the discussion on papers, watts etc. :D

I notice on my new "ride" (1 Litre, 3 cyl Petrol) that the battery is, well, tiny. I mean really tiny. I have an old style MGB which was designed with 2x 6 volt batteries of which I have 2 new ones, but the one in my new car is about the same size, if not smaller, than one of those.

Assume my Aygo also has a small alternator as it only has 3 cylinders and 998cc then surely there is scope for a reduction in size rather than a full elimination in other vehicles ?

My though line is this - take a typical car which has been stripped for hypermiling - e.g. a Civic or something else. If you have reduced the electrical load (removing AC, extra lights, etc.) then you can live with a smaller (Aygo, but also Chevrolet Matiz) sized battery which also saves weight, and also a smaller alternator because anything bigger is a waste of energy as the battery is so small.

That way you get the benefits of saving on the alternator load vs what the engine had rated originally, less weight in a smaller battery but also get the convenience of a constantly charged battery whenever you use your car - like a conventional car.

EDIT - PS - plus this is nuts and bolts mods which are the simplest.

The problem is many parts of the load you can't really do much ,at least on modern vehicle .
sure you can not use the Ac/heat, heated seats, rear defroster etc .
The things that eat up amps are things like fans , then you have the whole powertrain (ECU/ABS/VSA etc) so only thing you can do is not put any accessories but still the load will probably go over 15-30amp if cooling fans go on . Thats not counting headlights , I guess you could not drive at night but ...

Alternator already adjust output according to load so you would really have to strip/not use anything and still have a load .

Has any one with a V-belt setup tried to build a belt quick release?
A 10% gain is amaizing, but the drive ability aspect leaves a few holes to be filled in.

56W = 4A × 14V

...or, about 1/13th of one HP (746W)

I have seen people talking about it here, but I don't think it has been built. Unless I missed it in search this site. Use the search function. Have you considered an alternator kill switch? My understanding is that, "off," an alternator is not a significant drag. It produces drag when it starts generating--for small or large loads. What if you turned it off and only charged your deep cycle battery when your voltage gauge told you it was needed--and then only while coasting?

Since I have a work truck that does more than move my butt around I was already planning on installing Marine starting and deep cycle batteries at some point (stock configuration is for 2 large batteries). I have a small 700 watt power inverter installed now and will likely get a much larger pure sine wave installed in the near future for running tools with out a generator, also have a flood light and will likely install a spot light and i am ready to install a 50 amp 12v air compressor when I have the time. I have also converted over to electric fans, electric cooling pump and electric fuel pumps.
This is why I have to keep an alternator for night time and PTO use.
I searched around and found:
"Electricly unhooking" the alternator seemed to net about a 5% gain.
Deleting or unhooking the belt seemed to be the real money maker, +10%MPG.

Just running off battery power alone isn't that appealing since each large marine starting battery I have been eyeing will run nearly $180 each.

I had already been considering a small solar panel to keep the batteries topped off in winter, now I am thinking about scaling that up.

I have been playing around with trying to design a circuit to replace/augment the rectification diodes with MOSFETs. I keep running into singularities at the moment but I will try and publish the results and circuit I come up with later.

I might be able to drop load on the engine by 1/4th a HP for every 30 Amps drawn.

So possibly half the gain is from disconnecting the belt? That would put the lie to what I was told about the big gain being in preventing the alternator from generating power.

For a solar panel, you might consider this company: 100w Solar Panel battery charger f boat,car.waterproof | eBay
They are the folks I have considered. The panel is thin and flexible, and I can fit a panel large enough for 120w on my Civic roof.

I think it depends a lot on alternator speed and load.
You car guys are running your alternators on the highway at high speed with lowish draw (5 to 15) amps from an alt spinning at least 6,000 up to about 9,000.
I am sure I would see more than a 5% gain if I put enough solar on top of the suburban to run the electrical system since the alt runs at 100%+ at lower speeds.
I run my alternator at about 3,600RPM on the highway drawing up to 20 to 25 amps.
Using solar to cover coolant pump, fuel pump and fan losses sounds nice.

To sum it up I think I have more to gain by removing the electrical load only and you have more to gain by deleting the alt or removing the belt.