[chansen]

Just finished my conversion and I was wondering, should I try to keep the RPMs low to achieve the best range? I suspect low RPMs in 3rd gear might draw higher current and loss of range vs just letting the warp9 motor spin faster in 2nd.

[Amberwolf]

Very basically:

Faster the motor spins, the higher the BEMF, so the less current it draws; letting the drivetrain do the speed-to-torque conversion to get similar power output to the wheels for less battery current used.

It could be explained a lot better by many others here, but as I understand, that's the gist of it. It certainly works on my CrazyBike2 that way.

[kek_63]

Search the Wiki and the forum - this comes up often.

Simplest answer - Low rpm = high amperage = low efficiency+heat

Keith

[tomofreno]

I think that's a good way to look at it. Power is the product of torque and angular velocity. Running in a lower gear means the motor has higher shaft angular velocity for a given wheel velocity. The motor power is then the product of a lower torque and higher shaft velocity and is equal to the power at the wheels which is the product of a lower angular velocity and higher torque due to the mechanical advantage of the overall gear ratio of the vehicle. Motor torque is pretty much proportional to current, so less current is required to produce the lower motor torque. So as you say, for better efficiency you want to use the mechanical advantage of the gearing to transform a lower motor torque to a higher torque at the wheels, so less current to the motor is required.

Tom

[chansen]

I'm doing some "field" tests on this by measuring the DOD on multiple daily commutes (20 miles) in which I either use 2nd or 3rd gear for the whole trip. It will take me a month or two to collect enough data that it becomes statistically significant. I will post the results when I am done.

Thanks for the tips.

[Bowser330]

Originally Posted by chansen

I'm doing some "field" tests on this by measuring the DOD on multiple daily commutes (20 miles) in which I either use 2nd or 3rd gear for the whole trip. It will take me a month or two to collect enough data that it becomes statistically significant. I will post the results when I am done.

Thanks for the tips.

awesome...thanks chansen!

[Astronomer]

Can't someone with a current meter on the dash just run a short course two times in two different gears and simply observe which requires more amps?

[roflwaffle]

What are the 2nd/3rd gear ratios, axle ratio, and tire size? You should be able figure out what's best for efficiency from the Warp 9 map. Generally speaking, 2000-4000rpm is where you want to be.

[Bowser330]

Originally Posted by roflwaffle

What are the 2nd/3rd gear ratios, axle ratio, and tire size? You should be able figure out what's best for efficiency from the Warp 9 map. Generally speaking, 2000-4000rpm is where you want to be.

I think his setup is for 120V. The graph you reference is for 72V.

Does the voltage make a difference what rpm range is most efficienct?

[E4mula]

Originally Posted by Astronomer

Can't someone with a current meter on the dash just run a short course two times in two different gears and simply observe which requires more amps?

I've run some tests like that. Constant speed over the same course through different gears. Average power consumption over the course increased when shifting into higher gears.