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RegGuheert
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Brake lights with regen...

Mon May 28, 2012 4:36 pm

I generally have a concern that if I am slowing rapidly that those behind me should have some warning. Others here have expressed that they use D when in traffic so that they will have to use their brakes to slow down in traffic, thus warning drivers behind them.

Given this, perhaps it makes sense to also have the brake lights come on beyond a certain level of regenerative braking, even if the driver does not have their foot on the brake pedal. That seems to match the intent of the brake lights.

Perhaps it could come on beyond 25 kW of regeneration and go off below about 20, giving it a fair amount of hysteresis so that it does not flicker on and off to quickly.

I can imagine this might eventually become a requirement as future EVs may have significantly more regenerative braking power than the current crop.

Thoughts?
RegGuheert
2011 Leaf SL Demo vehicle
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surfingslovak
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Re: Brake lights with regen...

Mon May 28, 2012 4:44 pm

RegGuheert wrote:I can imagine this might eventually become a requirement as future EVs may have significantly more regenerative braking power than the current crop.

Thoughts?

The ActiveE does this. Not 100% sure about the Tesla Roadster, but I think it uses brake lights on regen as well. It's worth noting however, that when you let go of the accelerator pedal, both vehicles slow down much more aggressively than the Leaf in ECO mode. Check out a recent discussion on this topic in the ActiveE Facebook group

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abasile
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Re: Brake lights with regen...

Mon May 28, 2012 5:44 pm

For our purposes, I'm happy with the current behavior. In the mountains where we do most of our driving, having brake lights on ECO mode regen could be overkill and annoying, at least with the current level of regen. In ICE cars, drivers control speed on downgrades by downshifting, or in the case of the Prius, by using "B" mode, which does not turn on the brake lights.

On the other hand, a 20-25 kW brake light threshold might be helpful in more urban/suburban contexts, i.e., at signals and in traffic.

Adding a "B" mode, possibly with even stronger regen for downgrades, would be a reasonable way of making this selectable.
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surfingslovak
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Re: Brake lights with regen...

Mon May 28, 2012 5:56 pm

abasile wrote:Adding a "B" mode, possibly with even stronger regen for downgrades, would be a reasonable way of making this selectable.

Yes, I love that idea. While at it, they should also get rid of the creep or allow us to deactivate it. Leaf's brake lights are really high up, and I've noticed that they are shining directly into the faces of folks stopped behind me at a red light. I often put the handbrake on, so that I don't continue to blind them. In the ActiveE, I don't have to ride the brakes thanks to the strong regen. Not even at a full stop, since there is no creep. Yes, it takes some time getting used to, but you don't want to go back after that.
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Nubo
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Re: Brake lights with regen...

Mon May 28, 2012 7:56 pm

Logically, the brake lights should come on at some level of deceleration, regardless of the cause (brakes, regen, blended). Accelerometers are cheap and robust these days so it would seem reasonable to use them to trigger the brake lights.

On the other hand, the LEAF's regen is mild enough to where I don't think it presents a problem for following motorists. It's certainly no more intense than even a 4-cylinder manual transmission ICE using engine braking.
I noticed you're still working with polymers.

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Electric4Me
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Re: Brake lights with regen...

Mon May 28, 2012 10:50 pm

Nubo wrote:Logically, the brake lights should come on at some level of deceleration, regardless of the cause (brakes, regen, blended). Accelerometers are cheap and robust these days so it would seem reasonable to use them to trigger the brake lights.

On the other hand, the LEAF's regen is mild enough to where I don't think it presents a problem for following motorists. It's certainly no more intense than even a 4-cylinder manual transmission ICE using engine braking.

No need for an accelerometer. I think some previous car (AC Propulsion's T-Zero?) simply knew when the motor was slowing down since its RPM is constantly monitored and turned on the brake lights when some deceleration threshold was reached. I'm sure the Leaf is actively monitoring RPM too.
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Nubo
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Re: Brake lights with regen...

Mon May 28, 2012 11:20 pm

^^ good point :)
I noticed you're still working with polymers.

Herm
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Re: Brake lights with regen...

Tue May 29, 2012 4:51 am

I'm sure the Leaf has several accelerometers already, used by the air bags and ABS system... it would be nice if Enginier modded the regen out of the gas pedal and into the brake pedal where it belongs, then you would not have to worry about the brake lights.

jkirkebo
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Re: Brake lights with regen...

Tue May 29, 2012 6:03 am

Herm wrote:I'm sure the Leaf has several accelerometers already, used by the air bags and ABS system... it would be nice if Enginier modded the regen out of the gas pedal and into the brake pedal where it belongs, then you would not have to worry about the brake lights.


Funny, I'm waiting for him to mod the regen out of the brake pedal and put everything on the gas pedal where it belongs ;)

BTW, the cruise control uses what regen is available on the gas pedal, so less regen available for the CC in D than in eco. If you mod all the regen out from the gas pedal, CC won't be able to use any regen at all and thus rendering itself useless.

Herm
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Re: Brake lights with regen...

Tue May 29, 2012 6:38 am

jkirkebo wrote:Funny, I'm waiting for him to mod the regen out of the brake pedal and put everything on the gas pedal where it belongs ;)


I'm not going to criticize you for wearing out the battery prematurely or wasting power.. for all I know you may have a photovoltaic system :)

Good point on the cruise control.. perhaps Enginier can put a 3 way switch on his mod. I would like a momentary switch on the steering wheel to disable regen, or perhaps just drop the car into neutral, back to drive when the switch is released.

Some would say if you need to use the brakes you are driving too fast for the local conditions.

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