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Old 07-12-2010, 11:34 PM   #1 (permalink)
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Is Regenerative Braking Real? Does it work as we thought?

Is Jack Rickard correct about there being zero gain -- or even a loss, when regenerative braking is used in an EV?

If you have an EV, can you try to duplicate his results? He is even seeing a 7% *loss* when regenerative braking is used.Like him, I am very surprised at these results -- they make no sense.

EVTV.ME: More Regenerative Braking Results. It gets worse...

He is already working with Illah Nourbakhsh (at Carnegie Mellon), so hopefully we can sort this out?

Regenerative braking in the Aptera - is it merely dogma? - ApteraForum.com - Unofficial Aptera Car Forum

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Old 07-12-2010, 11:41 PM   #2 (permalink)
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FYI, when looking at using a freewheel on my bicycle vs a fixed gear, the figure I saw was that the regen would return %18 of what you put into it, and the constant friction reduced the bikes ability to coast well beyond what you would get back from %18 of your braking energy. So most bike sized EVs opt for free-wheel.

Not an EV only problem though, hybrids have the same concern.
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Old 07-12-2010, 11:51 PM   #3 (permalink)
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The three modes that Jack Rickard tested (on the first car) included one where it could coast freely, and only had regen on the brake pedal. This still returned no better results than when *no* regen was used...

Something does not compute. And Jack is puzzled, too.
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Old 07-12-2010, 11:57 PM   #4 (permalink)
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Regen works on my (PH)EV. Evidently, when he replaced his DC motor and controller with AC, he selected less efficient components.

Also, he was talking about being constantly in regen or assist. If he doesn't have a neutral position in his transmission, then he needs a "zero amps glide" setting on his throttle. DWB and long coasts work better than regen.
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Old 07-13-2010, 06:11 AM   #5 (permalink)
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Didn't check the links but I'll say that a properly driven vehicle doesn't usually need much braking at all on the non-urban flatlands so regen maybe wouldn't be worth any cost/equipment penalty, but I've spent enough time in hilly areas to really, really wish I had regen there!
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Old 07-13-2010, 08:20 AM   #6 (permalink)
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What is he using a the regen element, the motor rotor? or and independent charge item like edy brakes?
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Old 07-13-2010, 09:20 AM   #7 (permalink)
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Yeah I'm not sure what systems hes using either, but if the regen setup is working correctly its going to recapture energy, period. Sounds like his system isn't properly designed, or his testing is flawed.
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Old 07-13-2010, 10:22 AM   #8 (permalink)
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Old 07-13-2010, 10:32 AM   #9 (permalink)
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I know regen works on my Prius. But it's set to about 10% of max with the the throttle off (to simulate engine braking on a conventional car). I usually apply just enough throttle to eliminate the regen when I want to coast - the Prius has a display that tells the driver when the regen is on and off so it's easy to modulate. Then when I approach a light or stop sign, I let off the throttle and let the regen resume and apply just enough brake (trying to stay within the regen zone so as not to engage the mechanical brakes) to get a smooth stop. I know the regen is working because I can see the battery charge level rise.

Possible reasons why the tester didn't see a benefit from regen:

A) Different conditions between tests.

B) Didn't do the math correctly.

C) Regen level set too high so that he was "hunting" between regen and applying power to maintain speed, wasting energy (due to system losses) along the way.
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Old 07-13-2010, 11:10 AM   #10 (permalink)
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I vote for C. Neutral coasting would be better in most cases.

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