GRA
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Re: 3D GPS, Cruise Control

Sat Feb 18, 2012 3:05 pm

dgpcolorado wrote:
garygid wrote:I think, for better Safety, the EV should turn ON
the brake light at ANY Regen level.
That would mean brake lights on the whole way down a hill. Doesn't having brake lights on all the time lose the startle factor that warns the following driver of a speed decrease?

Using mild regen going down a hill is similar to descending a hill in a lower gear in an ICE car, the usual technique used by any competent driver on hills. (The rule-of-thumb is that one descends the hill in the same gear as is used to climb the same grade.) As it happens, the Eco regen slows the LEAF quite a bit less than third gear on my ICE cars; I wish it could be dialed up a bit so I can reduce my speed going down those grades without having to use brakes.

Descending a grade in a lower gear or using regen doesn't involve slowing if the grade is relatively constant, so there is no need to warn following drivers with brake lights. It is only the sudden change in speed that needs brake lights, IMHO.
Agreed, I see no need whatsoever for linking regen to brake lights, no matter how high the regen is (and the Leaf definitely needs a 'B' mode). When you get on the brakes it should be a relatively rapid but short-turn decel, which is different from descending a hill with a steep grade in a lower gear. In the latter, you use the brake pedal only when the speed has crept up faster than you want and you need to slow for a turn or what have you. I'm often amused, occasionally alarmed, to see someone riding their brakes all the way down a long hill instead of shifting to a lower gear and letting engine compression (in an ICE) slow them; even if their brakes aren't smoking at the bottom, you can usually smell them. As my dad (a truck driver) taught me, "use your brakes intermittently so they can stay cooler, and save them for emergencies; always use primarily engine braking for any long or steep descent. If your transmission fails, you can replace it. If your brakes fail, you can't replace you!"

If you need brake lights on to maintain a safe distance behind someone while descending a hill you shouldn't be driving a car in the first place, because your head isn't in the game.
Guy [I have lots of experience designing/selling off-grid AE systems, some using EVs but don't own one. Local trips are by foot, bike and/or rapid transit].

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DaveinOlyWA
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Re: 3D GPS, Cruise Control

Sat Feb 18, 2012 3:07 pm

not arguing that point but on flat ground, its a much different story
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; 11,333.1 mi, 93.73% SOH
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garygid
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Re: 3D GPS, Cruise Control

Sun Feb 19, 2012 10:31 am

1. Down-shifting and using engine-compression for braking ...
does not really apply to a LEAF.

One's head must be in the game called: "Regen or Brake".

And, when Regen is not available, the "game" has few options.

2. Any action that will "noticably" reduce the car's speed should turn on (or flash) the brake lights.

Perhaps just starting to reduce pressure on the "Go-Faster" (pedal) should flash the brake lights as an early warning of possible impending slowing.

I think that extra (roughly) half-second warning (of a sudden slowing) would save some lives, much inconvenience (having the rear end of your car repaired), and a lot of insurance dollars!
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TomT
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Re: 3D GPS, Cruise Control

Sun Feb 19, 2012 10:56 am

It's no different than selecting a lower gear in an ICE - something I often do - and that doesn't turn on the brake lights...
DaveinOlyWA wrote:not arguing that point but on flat ground, its a much different story
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garygid
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Re: 3D GPS, Cruise Control

Sun Feb 19, 2012 11:14 am

Such "unannounced slowing" is one of the defects of modern ICE vehicle design.

Possibly, some "Repair Shop Consortium" has a lobby against improved "slowing warnings"!
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Nubo
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Re: 3D GPS, Cruise Control

Sun Feb 19, 2012 11:32 am

jkirkebo wrote:
garygid wrote:3. The CC does slow the LEAF using Regen, I believe. Perhaps you need more Regen due to steep grades? Can one use ECO mode's greater Regen with CC?
Yep, sadly the regen available in CC mode is tied to driving mode. So shifting to eco will give the CC more regen to work with.

In my opinion, CC should be able to command all the regen possible, regardless of driving mode.
I can see a possible safety issue. The max regen is variable based on SOC and (iirc) temperature. If you were going down a steep descent and gotten comfortable with CC using strong regen for speed control... and the computer decided to greatly reduce regen, it could lead to a startling "runaway" situation. By forcing the driver to use the brake pedal to get strong regen, they are ready to react.
I noticed you're still working with polymers.

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dgpcolorado
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Re: 3D GPS, Cruise Control

Sun Feb 19, 2012 11:35 am

garygid wrote:1. Down-shifting and using engine-compression for braking ...
does not really apply to a LEAF. Not really true. Descending a hill on regen is analogous to engine braking on an ICE car, which is why we mention it.

One's head must be in the game called: "Regen or Brake". Although it was a bit unclear, I believe that GRA was referring to the driver of the following car, not the EV using regen.

And, when Regen is not available, the "game" has few options. In that case brakes are used, complete with brake lights.

2. Any action that will "noticably" reduce the car's speed should turn on (or flash) the brake lights. Agreed. What I was referring to was driving on regen at a relatively constant speed. Brake lights in such a situation don't make sense. I encounter this situation every time I leave my house, so it isn't some sort of "special case".

Perhaps just starting to reduce pressure on the "Go-Faster" (pedal) should flash the brake lights as an early warning of possible impending slowing.

I think that extra (roughly) half-second warning (of a sudden slowing) would save some lives, much inconvenience (having the rear end of your car repaired), and a lot of insurance dollars! What I would like to see is brake lights tied to deceleration. For example: lights come on at -0.2g and go off when deceleration is reduced to -0.1g. (Those numbers are just guesses on my part, I don't know what really good figures would be.)
The reason I mentioned all this is that my impression is that flatlanders are completely unaware of the use of regen to descend hills at constant speeds and that they assume that regen=braking=rapid slowing. This is not true when going down hills of significant grade; in that case regen is used to offset the acceleration of gravity. I do not want my brake lights to come on unless I am slowing at a significant enough rate to present a hazard to the following driver.
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GRA
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Re: 3D GPS, Cruise Control

Sun Feb 19, 2012 4:22 pm

dgpcolorado wrote:
garygid wrote:1. Down-shifting and using engine-compression for braking ...
does not really apply to a LEAF. Not really true. Descending a hill on regen is analogous to engine braking on an ICE car, which is why we mention it.

One's head must be in the game called: "Regen or Brake". Although it was a bit unclear, I believe that GRA was referring to the driver of the following car, not the EV using regen.

And, when Regen is not available, the "game" has few options. In that case brakes are used, complete with brake lights.

2. Any action that will "noticably" reduce the car's speed should turn on (or flash) the brake lights. Agreed. What I was referring to was driving on regen at a relatively constant speed. Brake lights in such a situation don't make sense. I encounter this situation every time I leave my house, so it isn't some sort of "special case".

Perhaps just starting to reduce pressure on the "Go-Faster" (pedal) should flash the brake lights as an early warning of possible impending slowing.

I think that extra (roughly) half-second warning (of a sudden slowing) would save some lives, much inconvenience (having the rear end of your car repaired), and a lot of insurance dollars! What I would like to see is brake lights tied to deceleration. For example: lights come on at -0.2g and go off when deceleration is reduced to -0.1g. (Those numbers are just guesses on my part, I don't know what really good figures would be.)
The reason I mentioned all this is that my impression is that flatlanders are completely unaware of the use of regen to descend hills at constant speeds and that they assume that regen=braking=rapid slowing. This is not true when going down hills of significant grade; in that case regen is used to offset the acceleration of gravity. I do not want my brake lights to come on unless I am slowing at a significant enough rate to present a hazard to the following driver.
Yes, In the situation described, if you tied brake light activation to decel rate I could see it. I think that's what Dave was referring to, a situation of rapid decel in a car with high regen and doing single-pedal driving, such as stop-and-go traffic. The question is whether this is worth the extra cost and complexity of providing an extra circuit to the lights and some kind of decel sensor.

And yes, in my earlier post I was referring to the driver of the car following the one using regen.
Guy [I have lots of experience designing/selling off-grid AE systems, some using EVs but don't own one. Local trips are by foot, bike and/or rapid transit].

The 'best' is the enemy of 'good enough'. Copper shot, not Silver bullets.

DaveinOlyWA
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Re: 3D GPS, Cruise Control

Sun Feb 19, 2012 7:56 pm

i know a lot of drivers around here that will frequently hit the brakes hard enough to engage brake lights without actually engaging the brakes just as a courtesy just to let someone in the back there might be a need to slow down soon

in the Prius i have done it as well since i have a tendency to slow down way in advance if i see brakes lights up ahead.
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; 11,333.1 mi, 93.73% SOH
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GRA
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Re: 3D GPS, Cruise Control

Tue Feb 21, 2012 2:50 pm

DaveinOlyWA wrote:i know a lot of drivers around here that will frequently hit the brakes hard enough to engage brake lights without actually engaging the brakes just as a courtesy just to let someone in the back there might be a need to slow down soon

in the Prius i have done it as well since i have a tendency to slow down way in advance if i see brakes lights up ahead.
I'm the same (or I turn on the emergency flashers briefly, if I can see a rapid slow-down ahead), which is why I question the need for a special circuit. Ultimately, any need for one won't be settled until the IIHS has gathered enough data from cars with and without such a circuit, and the latter show a statistically significant increase in getting rear-ended.
Guy [I have lots of experience designing/selling off-grid AE systems, some using EVs but don't own one. Local trips are by foot, bike and/or rapid transit].

The 'best' is the enemy of 'good enough'. Copper shot, not Silver bullets.

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