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dutchboy 07-06-2009 12:51 AM

Non-hybrid Generative Braking
Has anyone explored the possibility of removing the alternator from an ICE vehicle and implementing Generative Braking to charge the batteries by hooking up the alternator (or a beefier alternator/other electric motor) in order to generate electricity for charging the battery?

I think I've seen something where someone tried to run a belt off a half-shaft... I am thinking more along the lines of using the non-drive wheels to spin an alternator for braking/energy recovery purposes.

I'm thinking an alternator wouldn't really be able to provide the electomagnetic resistance needed to slow the vehicle down much and that a larger electric motor would be needed.

At that point, the difference between going fully hybrid would be a bank of batteries and a motor controller (no small cost to be sure).

Bicycle Bob 07-06-2009 03:15 AM

See Do-it-yourself regenerative braking? - Fuel Economy, Hypermiling ...
among many other threads on the topic here.

Ryland 07-06-2009 09:26 AM

Not a new idea, nor a new topic on this forum.
Most common way to do this is to replace the alternator with larger one that is switched on when the engine is under very low loads but still connected to the drive wheel, a 60amp alternator can put out 750 watts or more, around 1hp worth of power trying to slow the car down.

Daox 07-06-2009 10:17 AM

You don't really want to charge a 12V battery much higher than 60A I don't think. Short bursts would be fine, but sustained charging @ 60A would heat that thing up quick fast. The downside here is 1hp of braking is next to nothing if you need to slow down fast at all.

chuckm 07-06-2009 02:30 PM

I'd be curious if you could charge at higher amps by connecting to a ultracapacitor... maybe use it buffer the battery.

Daox 07-06-2009 02:57 PM

Thats a pretty good idea Chuck. I'm sure you could, but you'd need to find a way of controlling the amperage from the cap to the battery.

chuckm 07-06-2009 07:28 PM

Hmm.... What if you set ultracap to have a voltage of 13.7V (lower than the normal rest voltage of the battery)? Could you use the battery's internal resistance to regulate amperage from the ultracap (which would only discharge when the electrical system is loaded enough to cause voltage sag or when the battery is discharged that much)? Put a diode between the ultracap and the battery to ensure that current only flows to the battery, not the other way.

Ryland 07-07-2009 11:52 AM

Lead acid batteries can handle a very high charge rate for a short amount of time, this has been proven in electric vehicle racing and tested by battery companies, but you don't want to do more then a 50% charge in 3 minutes and even that kind of charge shortens the battery life a great deal, you have to have good connections tho or you will melt battery posts.
If you want to recapture that energy you are going to need a bigger battery of course, so this conversation about over charging is pointless as the starting battery in my civic holds enough energy for about a mile of range, so figure at best a mile and a half of braking energy, shorten that by half or more if it's a steep hill, so to give good battery life you shouldn't work the batteries that hard, so I would say put 4 of them in for a mile of braking.
I think that getting a regenerative controller, an Etek motor and a modest size bank of batteries would be the way to go if you want to do this, just replace your alternator with the Etek motor.

Bicycle Bob 07-07-2009 12:07 PM

Ni-Cads are very good for taking a fast charge. The generator can be sized for very intermittent duty, like a starter motor, and made light rather than particularly efficient. However, even pure electric cars need mechanical brakes for the peak loads. With a reasonable size dedicated electric brake, you'd still spend a lot of time slowing down. I don't know if it would pay off.

stevey_frac 07-07-2009 01:09 PM

With a decent size enough motor, could you put say, 5 HP back onto the road through the alternator belt? If you could, that would seriously improve your city mileage.

Not worth the cost though likely.

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