Decreasing large DC motor power usage by coasting I'm working on a class project - an electric bike competition. Part of the requirements for the final grade is having a "race advantage system" on your bike. Basically, just something unique that will give you an edge in a final competition where the winner is the bike that goes the furthest on motor power in half an hour. Speed doesn't matter. I was thinking of using an Arduino is some way to do this.

We're using 2 12 volt, 7 amp hour batteries which could be powered in series or parallel. The motors are pretty large, I didn't get any specifics on them though.

My idea was to let the motor coast when it reaches a certain speed, and to turn it on again once it goes under it. I would have to do this with a relay because of the high amounts of electricity we're working with (unless someone knows of a transistor that could handle that while being powered by an Arduino, but I couldn't find one).

My question is: Would repeatedly coasting and starting the motor based on the bike speed increase the "lifetime" of the motor on limited battery power?

The only concern I have is starting the motor again. I'm afraid that could be the point where the most power is consumed, and would make this idea useless. I've searched for similar things online, but I haven't found anything about it. I hope this fits in Arduino, I wasn't sure whether to post it here or electronics.
I suggest you also consider the load going up in inclines. if you turn off the engine going uphill based on speed, you're most likely to turn it on again soon because of the load. You might be able to get a hint of load from the current drawn by the motor. Combining speed and load might also optimize your bike going downhill.