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Power use at a stop light

Sat Oct 30, 2010 3:27 pm

Does Leaf power the traction motor while stopped for a light? Since the Leaf will roll on its own power (idle?) with the brake off I am curious if that power is provided to the traction motor with the brake peddle holding the car.

Can Leaf be power braked? Apply power to the motor at the same time as the brake holds the car?
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Re: Power use at a stop light

Sat Oct 30, 2010 3:33 pm

Hmmn.....good question. I'd like to try that, now it's been suggested!
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Re: Power use at a stop light

Sat Oct 30, 2010 6:37 pm

Most likely the LEAF will only power the motor when the brake is NOT pressed.

Take the foot off the brake, and a little power goes to the motor to simulate
the ICE car's now-familiar (to most) automatic transmission "creep".
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Re: Power use at a stop light

Sat Oct 30, 2010 6:40 pm

Anyone know - why the auto has creep ?
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Re: Power use at a stop light

Sat Oct 30, 2010 6:46 pm

even my Prius has "creep", it's all about "simulating" the experience of an automatic transmission on an ICE car. I think it's not really needed, but all of the mfrs
seem to do it...
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Re: Power use at a stop light

Sat Oct 30, 2010 6:52 pm

Could be for safety. If you creep on a hill it is less likely to roll back after releasing the brake. If they allow power with the brake applied then there is no safety measure to cut power in an unintended acceleration so they may not allow power plus brake at the same time, the creep helps solve the roll back issue. And there is no mechanical e-brake to rely on like in a manual. Drive a stick Audi with an electronic parking brake and on a steep hill and see how it differs..

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Re: Power use at a stop light

Sat Oct 30, 2010 7:58 pm

evnow wrote:Anyone know - why the auto has creep ?
It's a function of the torque converter, which is the auto-tranny version of the clutch and pressure plate in a manual. It is basically a hydraulic coupling device--the auto tranny is never completely disconnected from the engine (as a mechanical clutch does in a manual), it is still spinning even when the car is at idle and stopped, and generating some torque from the circulation of the fluid inside, which is transmitted through the gears to the wheels (if the car is not in neutral). Depending on its "stall speed" setting, this "residual torque" may be enough to hold the car in place on a slight hill, or creep forward on the level if no brake is applied.

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Re: Power use at a stop light

Mon Nov 01, 2010 7:11 am

If nothing else, this would be nice to know as the constant term in the power equation. But it would also depend on Environmental Control Settings a great deal. If you're heating the cabin in winter most of your idle energy is probably going into the coils.
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Re: Power use at a stop light

Wed Nov 10, 2010 3:02 pm

if the Leaf is sitting still at a stop light - assuming that the climate control is OFF - in READY MODE, the only power consumption is being drawn from the lead acid battery (low voltage). the traction motor requires no high voltage current in the idle state.

in other words, leaf sitting still (climate control OFF) is no different than any car sitting with ignition in ACC


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Re: Power use at a stop light

Wed Nov 10, 2010 3:05 pm

That doesn't explain the high Wattage shown at idle. (250W?)

What about the brake booster? The soft-start "tug" at the wheels to make it feel like an automatic?
Inverter leakage/losses?

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