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Old 11-20-2007, 06:43 AM   #1
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Regenerative braking?

I was thinking... In order to lessen the load on the alternator, or even make it easier to eliminate the alternator altogether...

Could you retrofit a regenerative braking system onto a non-hybrid car? Like find a junked insight or prius and pull the brake systems off them.

If you could, then braking would be far less of a worry for the hypermiler, and the alternator wouldn't have to work nearly as hard to keep the battery charged.

Or is it something far too complicated to fuss with?
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Old 11-20-2007, 08:02 AM   #2
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I would be interested in this as well, but I'm uncertain of the viability of doing it.

Then again, I can't weld. I'm sure if I could it would bea much easier project.
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Old 11-20-2007, 08:10 AM   #3
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The regen braking in the Prius is in the electric motor that moves the car not the wheels. It really is regen engine braking regulated by the gas pedal and brake pedal. There is no easy way to do it without some sort of transmission connection and maybe a clutch so you don't keep spinning the rotor of the alternator all the time.
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Old 11-20-2007, 08:28 AM   #4
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I've toyed with the idea of an AC clutch on an alternator that is coupled to a driveshaft.

Problem is that regen is only like 18% efficient when reused for traction, but it would be more efficient than having the alternator spinning with the engine as you could reclaim SOME energy lost in braking. There can be good mpg gains in no alternator (like up to ~%10), and if it is only used in braking then even better. But you would want to gear it such that it actually recharges when you brake, and would have to cycle it on hiway trips.
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Old 11-20-2007, 09:33 AM   #5
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How about some clutch activated device that winds up a spring or some elastic stuff. This would only be good for about one stop and one go but that should be enough. (A stop is always followed by acceleration.). The conversion efficiency should be pretty good.

Another idea would be to use some analogy to the "bottle rocket" with water and compressed gas to store and release a powerful burst of impulse. Air tools are very simple, robust and compact and have a high power to weight ratio. Efficiency is bad but maybe it could be improved a lot by using a fluid in the system. I wonder if the compressed gas can be taken directly from the exhaust system?
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Old 11-20-2007, 05:00 PM   #6
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Quote:
Originally Posted by Biffmeistro View Post
I was thinking... In order to lessen the load on the alternator, or even make it easier to eliminate the alternator altogether...

Could you retrofit a regenerative braking system onto a non-hybrid car? Like find a junked insight or prius and pull the brake systems off them.
Other projects (including getting my solar panel wired into my car's battery) are still a higher priority. However, considering my successes with lowering electrical usage (but keeping the alternator hooked up), and the reported successes of others disconnecting their alternator, I have toyed with the idea of having a three position switch put on the dash:

Position 1) Normal alternator, just as I have now.

Position 2) Alternator is electrically (although probably not mechanically) turned OFF. By simply turning off the alternator electrically, I'll still suffer the "static losses" for spinning the belts/etc. But by electrically disconnecting the alternator, all actual "electrical drag" would be eliminated. And if the alternator is one of the many on the market that has an on/off "control wire/signal" with it, I could probably get away without even needing to use a relay to disconnect the alternator (and instead just play with the wiring to the alternator control signal on the alternator itself).

Position 3) This is the key "pseudo-regen" position. In this switch position, the actual alternator control signal comes from the same car circuit that the brake lights are wired up to! By doing it this way, the alternator is off normally, but turns on the instant your brake lights come on. While the brake lights might not be the best "regen braking" control out there, they are easy to wire up to, and they do at least signify that you intended to slow down (so they aren't a totally unreasonable control either)!

NOTE: I would suspect that such an arrangement would give you more "regen braking" than you get normally with the alternator connected all the time. The reason I suspect this, is that alternators do put more drag on the engine when more electrical power is needed. And more electrical power is clearly needed (to charge the battery, if nothing else) if your battery is running a bit low (as it likely would be if/when you have otherwise been running with the alternator turned off). So such a wire setup may actually save wear on the brakes (by giving you more regen braking than normal), even more than it might help you go with "alternator off" for extended periods of time.

Again, this isn't a complete solution. It's just a thought for one cute way to retrofit a limited "regen braking" mode into an (optional) "alternator off" switch. And since I've not actually tried this myself, YMMV. But unless I'm missing something in my tentative design, this should be reasonably easy to wire up, as well as at least moderately effective. But I guess we will have to wait until someone tries it, to know for sure...
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Old 11-20-2007, 05:08 PM   #7
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Maybe a good idea to get into the alternator and drop the output voltage a bit normally then bump it up to full voltage when braking or down hill with your foot off the gas. Next step would be a bigger more efficient alternator that can put a bigger load on the engine when you need it to charge. Only problem is the battery takes a beating.
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Old 11-20-2007, 05:30 PM   #8
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I think BMW has some alternator smarts so that it works more for some regen. There's many little things they auto manufacturers could do if it got into a features war on less expensive cars: autostarts, electric water pumps, steering, AC etc...

I'd love for vehicles to come with a 110 volt plug and the option to set a timer for warming up the interior and a warmer engine. it could monitor when to start the block heater and then the interior preheat based on outdoor temperature. Smart outlets in malls would help.

Heck if you had those pay plugs in parking lots and had a fast charge short range EV or vehicle that can go EV for short trips it would be ideal if there is greener electric capacity. If uou could get the loads and distances low enough then the they could do another short hop 10 miles maybe, after maybe 45 minutes... dunno, but it would be interesting.
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Old 11-20-2007, 06:25 PM   #9
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Mechanically it may be feasible, but not as a practical application on a non-hybrid because there simply isn't enough of a voltage requirement in the first place.

I got to a point it's not so much about the mpg anymore, it's about how long a tank of fuel lasts. I can drive slightly more aggressive and don't have to hold up ten miles of traffic so long I leave the car home most of the time, so to me the biggest booster is not driving.

I was amazed, it consumes NO gas when the engine isn't running
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Old 11-20-2007, 11:22 PM   #10
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I'll contribute a few ideas:

- A turbo driven alternator
- Having an alternator being driven by fluid in an automatic transmission. Then you can charge a battery more and brake at the same time by downshifting.
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