# Hill starts, using motors to keep from rolling backwards



## drolsinatas (Jun 9, 2008)

I have a direct drive EV, so on hill starts, the car rolls back a little before I hit the throttle. Sometimes the car will cut out, and I have to re-start the car in order to get it to work again.

My girlfriend likes to keep her foot on the throttle a little, to keep the car from rolling back. This worries me, but I'm not sure if I should worry.

Is it bad to be drawing amps to use the motor as a way to keep the car from rolling back on hills? Then after a minute or so pump more amps to get it going?

Sounds like a bad idea, but I don't know.


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## DVR (Apr 10, 2008)

Agreed.
If you are using current to hold the car it is basically a stalled motor and it will generate heat. not good.


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## major (Apr 4, 2008)

drolsinatas said:


> Is it bad to be drawing amps to use the motor as a way to keep the car from rolling back on hills? Then after a minute or so pump more amps to get it going?
> 
> Sounds like a bad idea, but I don't know.


Hi drolsinatas,

Yeah, that should not be done. Drawing current in a stalled motor will heat up the commutator bars under the brushes. Too much heat will distort the copper bars and cause them to "lift". Which then causes a clicking sound and rapid brush wear and sparking. If this has in fact already happened, you will need to have the comm turned and undercut by a pro.

On hills, since you don't need a third foot for the clutch, just keep the brake on and press the throttle down when you launch. As your amps come up, release the brake and you should be off. This should give you only a second or two of current on the stalled motor.

Regards,

major

PS...I think I saw another post by drolsinatas saying he has an AC motor. In that case, forget the comm bar problem. The stalled motor (for AC) isn't nearly so bad. But why waste the energy. Still use the brake and launch as I suggest.


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## adric22 (Jan 17, 2008)

I'm not sure what difference it makes for direct drive. I have a transmission but I have the same problem. I have to go through a traffic jam every morning and the traffic jam climbs up this one steep hill. So I'm constantly stopping and starting. However, it has never been a problem as I just hold my foot on the brake until it is time to move. Sometimes the car rolls back 6 inches or so. I don't have a clutch in mine so it isn't like working a gas car where you have to constantly slip the clutch to take off. However, I never just sit there for long periods of time holding the car in place with the electric motor.


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