EV Transmissions and Reducing RPM's at Speed

by Mark
(San Jose, CA)




I have read a bit about the question about the need or non-need for a transmission. Maybe I am still stuck in the gasoline mode, however it would seem to me that if I were to re-gear the rear end of the vehicle I am converting, such that my 2nd gear is now a 1st gear and then the rest of the gears are "up'd" that it would, at speed reduce the load on the motor, thus reducing the drain on the batteries. Am I right or am I just blowing smoke?

Hi, Mark!
No, you're right. That's pretty much how it's done.

Except that in practice you really only need two gears to get to freeway speed; Take-off (yes, 2nd gear is generally the one used for this), and Fly.

A transmission is useful in principle, if it's doing the job it was designed to do.

It's just that in the real-life scenario of converting a car from gas to electric, the transmission that your car came with is not really compatible the most common electric car conversion motor, which is a series wound DC motor. They're all low-end torque and flat curve at the top, like a golf cart.

The rest of the story is that most folks want to do the least amount of work possible on their EV conversions, and learn the least amount of new stuff necessary to get the job done. (This only makes sense when you want to maximize the bang for your buck, I'm not knocking it.) So they leave the transmission right where it is - it eliminates having to pull it out and sell it or junk it or whatever - and fix a couple of gears in place, and voila!

Some of the hybrids are using a variable speed transmission or CVT - whatever it's called - and I get the feeling this is going to be the EV transmission of the future.

Regards,
Lynne

Click here to post comments

Return to Motor Q&A.