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TomT
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Re: Wonder how the AC and brakes work while not moving????

Sat Jul 16, 2011 8:36 am

No, the brakes use an electromagnet actuator as a booster. There is no pump of any kind. There is a super capacitor in the back next to the charger to provide backup power for the brakes in case of a total electrical failure of the vehicle.

saywatt wrote:OK, so if we strip off all the semantics:
The brakes, which I mistakenly included in the original post, use a hydraulic pump with a kind of motor component.
Leaf SL 2011 to 2016, Volt Premier 2016 to 2019, and now:
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Herm
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Re: Wonder how the AC and brakes work while not moving????

Sat Jul 16, 2011 9:12 am

Its all semantics.. the impression I get is that brake motor helps you push down on the pedal, or does the foot pedal regulate (plus the brake computer) the amount of hydraulic pressure supplied to the calipers?. The pressure is generated by a rotating motor.. I believe the capacitor bank will supply emergency power to this motor if the main supply is not available but you can see where the brake pedal directly will provide a totally human powered failsafe.

It would be interesting to see if this system will be used in other cars, diesels and some fancy gasoline engines dont have lots of vacuum to power a vacuum brake booster.

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TomT
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Re: Wonder how the AC and brakes work while not moving????

Sat Jul 16, 2011 10:50 am

It's no different than any other power brake system where you have a hydraulic master cylinder that has some form of power assist. I doubt the vehicle codes would allow for any other form of brake system at this time...


Herm wrote:Its all semantics.. the impression I get is that brake motor helps you push down on the pedal, or does the foot pedal regulate (plus the brake computer) the amount of hydraulic pressure supplied to the calipers?. The pressure is generated by a rotating motor.. I believe the capacitor bank will supply emergency power to this motor if the main supply is not available but you can see where the brake pedal directly will provide a totally human powered failsafe.
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aqn
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Re: Wonder how the AC and brakes work while not moving????

Sat Jul 16, 2011 8:21 pm

mogur wrote:No, the brakes use an electromagnet actuator as a booster. There is no pump of any kind.
You will need to provide a reference for that assertion, because there is no mention of an "electromagnet actuator" in the LEAF service manual. Unless of course, by "electromagnet actuator" you were referring to the brake assist electric motor.

From the LEAF service manual, page BR-12:
• Based on the commands from the control module of the electrically-driven intelligent brake unit, the motor
inside the electrically-driven intelligent brake unit is operated and presses the master cylinder piston.
• Pressing the master cylinder piston, and brake fluid is sent to the ABS actuator and electric unit (control
unit).


saywatt wrote:OK, so if we strip off all the semantics:
The brakes, which I mistakenly included in the original post, use a hydraulic pump with a kind of motor component.
Herm wrote:Its all semantics..
Each of those components has a motor: brakes, steering and A/C.

mogur wrote:There is a super capacitor in the back next to the charger to provide backup power for the brakes in case of a total electrical failure of the vehicle.
Herm wrote:I believe the capacitor bank will supply emergency power to this motor [...]
Ingineerix apparently thinks that there is a single supercapacitor.
Anna Nguyen

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TomT
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Re: Wonder how the AC and brakes work while not moving????

Sun Jul 17, 2011 7:01 am

Look at the cutaway drawing in the service manual. It appears to look much more like a typical electromagnetic actuator (solenoid if you will) than an electric motor to me. I think the English translation lost a little of the context along the way...

The ABS system uses a hydraulic pump, of course, as do virtually all such systems on any kind of hydraulically braked vehicle.

aqn wrote:You will need to provide a reference for that assertion, because there is no mention of an "electromagnet actuator" in the LEAF service manual. Unless of course, by "electromagnet actuator" you were referring to the brake assist electric motor.
Last edited by TomT on Fri Jul 22, 2011 9:19 am, edited 1 time in total.
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Ingineer
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Re: Wonder how the AC and brakes work while not moving????

Wed Jul 20, 2011 11:32 pm

aqn wrote:Ingineerix apparently thinks that there is a single supercapacitor.
There is one capacitor assembly, but inside the box it's made up of numerous small supercapacitors soldered to a PCB.

Similar to this unit which is used on the Prius:
Image
(picture courtesy of Hobbit)

FYI: All 12v accessories on the LEAF are ultimately powered by the traction pack, so the nissan tech is right when he says the power steering is powered by the main pack. Also: there is a hydraulic pump on the ABS system.

-Phil
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EVDRIVER
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Re: Wonder how the AC and brakes work while not moving????

Wed Jul 20, 2011 11:38 pm

I thought it was a rat on a wheel. Now I need to find out the source of that noise.

Herm
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Re: Wonder how the AC and brakes work while not moving????

Thu Jul 21, 2011 4:06 am

probably the marbles you lost years ago are rolling around in the AC ducts :)

saywatt
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Re: Wonder how the AC and brakes work while not moving????

Thu Jul 21, 2011 10:56 pm

The important thing here, that we all must understand, is that the LEAF stops just fine with whatever technology it uses! :)

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Ingineer
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Re: Wonder how the AC and brakes work while not moving????

Fri Feb 17, 2012 8:48 am

The quick-and-simple answer is that if the average temperature is lower, it will take more energy. If the car gained no heat (insulated by a fictional perfect insulator) running the fan after the car was cool would actually use more power. Now, because of how we judge temperature, a 75 degree car with a fan blowing directly on you is going to feel a lot colder, so therefore you can make use of the fan and not cool the car as much to save electrons.

In the real world, if you cool the car down, (preferably on grid power from the EVSE) then it will not take as much to maintain it, but there definitely will still be heat load. This is made substantially worse if you have a darker colored car (paint and interior). This is one of the reasons I love white!

-Phil
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