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I have a partially electric car, a 2016 Toyota RAV4 hybrid. I have noted there are two ways I can hold the car on a hill at standstill. I can either press the brake pedal (after releasing it, there's an automatic hill hold that will hold it for a few seconds), or alternatively I can press the accelerator slightly.

I however have worried about the potential implications of holding the car on a hill by the accelerator for extended periods of time. I know that the electric motors are providing the same torque they would be producing by driving the hill up, and thus the current through the windings shouldn't be too high. However, even given that, the electric motors are at standstill, so if their cooling happens by air circulation, they won't be cooled.

So, is it harmful to hold an electric car on a hill by pressing the accelerator slightly? Are there any electric motor cooling issues?

  • Hill holding is going to use battery power, and a decent amount of it, so I would avoid it wether its harmful or not. I think after several minutes cooling might be an issue, but that's just conjecture. – JPhi1618 Sep 6 '17 at 20:12
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it depends on the electric motor type and the design. If the electric motor is a PM machine, dc currents are needed to hold the vehicle static. Even it is the same magnitude (id,iq) that will result in the same torque. When your vehicle is moving, ideally what are flowing in your inverter switches are 3-phase balanced AC currents. This means that 200A peak current only shows up once in a while because the currents are 3-phase AC currents whose magnitude are 200A. However, if the motor is at static, 200A DC will be given. And it will stress your inverter switches more. Of course, I hope that Toyota, as a famous company, has taken this into account and you don't need to worry as a customer.

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