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EVDRIVER
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Re: Regen and brake lights

Thu May 27, 2010 4:28 pm

johnr wrote:
LEAFer wrote:When the traction battery is "full" the energy from regen has nowhere to go (see discussion in another thread). And that causes an inconsistency, because the "go-faster" pedal behaves differently depending on current State-of-Charge :|
In the event the battery is full, the regen energy could be diverted to a resistive load. I have no idea if they will do that or not, though. And I really hope the go-slower pedal will feature variable regen, reserving the brakes to be applied *only* when it's impossible to stop fast enough with the regen alone.

Based on some new comments the regen is variable to more off accel but only in economy mode which limits acceleration which is irritating, also it sounds like the regen braking is a bit abrupt which means they don't have a great implementation.

Dav
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Re: Regen and brake lights

Fri May 28, 2010 2:02 pm

johnr wrote:In the event the battery is full, the regen energy could be diverted to a resistive load. I have no idea if they will do that or not, though.
<smiley mode>
That is one reason production has not actually started. What they plan to do in that case is have a big fan pop out the front of the car and help slow you down. They just haven't figured out how to get it to fit in the charge port door. :shock:
</smiley mode>

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Re: Regen and brake lights

Fri May 28, 2010 5:40 pm

planet4ever wrote:Well, the discussion I recall (don't remember which thread) concluded there were several places the energy could go, including having the regen work as usual but feed the current back to the engine's generator, which (acting as a motor) would spin the engine, just like in the bad old days. Naturally no fuel and no spark, but lots of compression and lots of heat for the radiator to dissipate.
What engine?????? The Leaf has no engine!!!! It's an electric car, remember? The energy from regen could be fed to a resistive load (as in train locomotives) but Nissan has not told us if the Leaf will do that or not.
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Re: Regen and brake lights

Sat May 29, 2010 1:19 am

DUH! Brain check. I've gotta stop looking at Volt forums.

[Truth is I'm only about 90% decided on the Leaf. With my low typical mileage requirements, either the Leaf or the Volt would work well for me. ... If only I could convince myself that GM is serious, and that they will provide any kind of price competition. I know, I know, the Volt is baroquely complex, but I do have a little problem that I confessed to over on "Wife Acceptance Factor".]
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Re: Regen and brake lights

Sat May 29, 2010 7:56 am

maybe an ultra Cap installed to take advantage of high regen situations. very small, light, so not a huge space consideration option to add. not sure of cost but guessing like any specialized application, someone will find a way to make it spendy
2011 SL; 44,598 mi, 87% SOH. 2013 S; 44,840 mi, 91% SOH. 2016 S30; 29,413 mi, 99% SOH. 2018 S; 25,185 mi, SOH 92.23%. 2019 S Plus; 412 mi, 99.72% SOH
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kballs
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Re: Regen and brake lights

Mon May 31, 2010 3:36 pm

I too prefer my pedal actions to be separated: foot on the accelerator pedal for acceleration, foot on the brake pedal for friction braking, no feet on any pedals for regen braking (like an internal combustion vehicle being in a low gear).

They will do this to some extent in eco mode, but also with neutered acceleration (it would make some sense to have an eco mode and an aggressive regen mode separately). If the traction control had trouble with really slippery conditions like snow and ice they could have a snow mode or just a control for how aggressive the regen is.

Tesla has done this part right, parallel hybrids have done it wrong (with their complicated jerky/uneven brake blending systems that are universally noted as an annoyance).

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garygid
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Re: Regen and brake lights

Mon May 31, 2010 5:31 pm

The 2010 Prius (a parallel hybrid) has very smooth blending of increasing Regen braking and then adding mechanical braking as the "go-slower" pedal is pressed.

It is a big mistake to have only one level of Regen braking.
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kballs
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Re: Regen and brake lights

Tue Jun 01, 2010 2:33 pm

It wouldn't be one level. You would modulate the regen power based on how far the accelerator pedal is lifted from the previous position... lift it a little and there is only a little regen, lift it a lot and there is a lot (then tapering off as the vehicle reaches the new target velocity indicated by the pedal position). The observed behavior from a driver's perspective is just like an ICE car in a low gear (except you don't rev the engine and guzzle gas when you press the pedal down and accelerate to 40+ MPH), it wouldn't be anything that weird from what many manual transmission drivers are already used to.

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Re: Regen and brake lights

Tue Jun 01, 2010 2:40 pm

kballs wrote:The observed behavior from a driver's perspective is just like an ICE car in a low gear (except you don't rev the engine and guzzle gas when you press the pedal down and accelerate to 40+ MPH), it wouldn't be anything that weird from what many manual transmission drivers are already used to.
But few people drive manual ... the customer user friendly behavior should imitate auto.
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garygid
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Re: Regen and brake lights

Tue Jun 01, 2010 9:32 pm

At high speed, one suddenly takes one's foot OFF the "go-faster", and ... what? ... sudden maximum regen-braking until zero mph is reached?

No, I do not think that strong, abrupt braking action would be acceptable!
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