Alternator modifications

[ConnClark]

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.

[JethroBodine]

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.

[Piwoslaw]

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.

[ConnClark]

Originally Posted by Piwoslaw

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

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

[California98Civic]

Originally Posted by brianjone5

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.

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?

[t vago]

Originally Posted by ConnClark

another paper

Automotive Power Generation and Control

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.

[brianjone5]

Originally Posted by California98Civic

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?

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

[California98Civic]

Originally Posted by brianjone5

Then how could someone who deletes an alternator see up to 10% mpg gain, as reported here?

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.

[t vago]

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.

[ConnClark]

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