trickle charge to reduce fuel?

[k-vette]

All of this talk about removing the alternator is other threads has got me wondering, what is the gain keeping the battery charged?

I already have a trickle charger. With no changes to the alternator or battery, will using my trickle charger each night increase mpg? Or is the benefit little to none? I'm sure it was answered somewhere, but couldn't find it.

[Piwoslaw]

1. There will be a gain, but hardly noticeable. The alternator is always striving to keep the battery charged, so the fuller the battery, the sooner the alt's load will be reduced. More and more cars have "inteligent" charging, ie the alternator only online when engine braking, unless the battery gets drained below a certain level.
2. The battery will live a longer, healthier life if it is kept topped off. Also, trickle charging is healthier than forcing energy in with a higher current.

[redpoint5]

Yes, but not worth the hassle.

If you want to actually see the fruits of your labor (fiddling with a charger), you will need to do an alternator delete or disable.

[Ryland]

I agree to a point, if you are driving a lot of short trips or shutting your engine off and coasting a lot then a trickle charger is a great idea because your battery needs an absorption charge to stay healthy otherwise it's voltage is always going to be low and the alternator is always going to be working extra to try to top it off but to fully charge and equalize it needs a longer slow charge.
About this time of year when I'm driving more and using my head lights more I'll top my battery off with a 2amp charge over night once every month or so, I thought my battery was on it's last legs 3 years ago but it's still healthy! saving $70 on not replacing the battery has been worth it.

[ksa8907]

i don't think it'll help much at all, unless you have a weak battery. alternators are run by the pcm adjusting how much charge it needs to create, after you start the car the alternator starts recharging the battery then puts out very low current until you turn the lights on, plug your phone charger in, turn the ventilation on, run the stereo, etc. even then, complete alternator deletes only net you about 10% IIRC.

[Cobb]

I cant speak for other cars, but Honda turns the alternator off and on by the ELD, so its on for the first 2 minutes or so of running, then when the battery voltage falls below 12.5 volts. Swapping out to a deep cycle battery and trickle charging should net the best results on any Honda. As an Insight owner and a slightly larger lead acid starter battery the results for improved mpg was for 15 for 7 miles or so, then it started to go down.

[Firestarter]

Kind of need DC power for spark. On a mechanical diesel sure.

What about using a wired ground so the load of the alternator is minimal until you use the brakes which then let's the alternator charge the battery

[brucepick]

Originally Posted by Firestarter

Kind of need DC power for spark. On a mechanical diesel sure.

What about using a wired ground so the load of the alternator is minimal until you use the brakes which then let's the alternator charge the battery

Using the alt to charge the system puts a load on the engine. The more amps it provides or puts out, the bigger the load the engine "sees". So you can charge the battery now or charge it later, same difference. If you want gains, use deep cycle(s) and charge them off the grid as suggested earlier. Grid=low cost.

UNLESS you are going down enough of a hill that even with transmission engaged to drive the alternator, you will arrive at end of your coast with same speed as if you had done EOC. In that case, you may as well charge off the alternator, driven by gravity. Admit it, usually anything that slows your coast will shorten it and reduce your overall mpg.

[Firestarter]

Originally Posted by brucepick

Using the alt to charge the system puts a load on the engine. The more amps it provides or puts out, the bigger the load the engine "sees". So you can charge the battery now or charge it later, same difference. If you want gains, use deep cycle(s) and charge them off the grid as suggested earlier. Grid=low cost.

UNLESS you are going down enough of a hill that even with transmission engaged to drive the alternator, you will arrive at end of your coast with same speed as if you had done EOC. In that case, you may as well charge off the alternator, driven by gravity. Admit it, usually anything that slows your coast will shorten it and reduce your overall mpg.

I meant... only charging the battery during braking. Using the higher amp draw to aid conventional braking so your sending kinetic body energy into a lithium ion polymer battery capable of taking a Huge charge instead of bleeding it off with brakes.

Would require a lipo battery. And ESC as well as modifying the brake pedal to use first few millimeters of travel souly for regenerative brake charging.

As for lowering mpg going downhill. I disagree. I live in the mountains and you can't just coast down the mountain without using the brakes so... using the alternator to keep speed in check over the brakes wouldn't hurt mpg.

[PaleMelanesian]

I EOC so much, the alternator has no chance of keeping the battery topped up. A few cents of electricity is cheaper than the dollars of gas consumed by leaving the engine running.