[ausev] Dual electric motor questions

[MLAB]

Chris Robison wrote:

> Through it's possible that one motor will draw slightly higher current
> than the other due to the small difference in back-EMF between the
> motors, I think the motors will share current pretty closely. I don't
> have direct experience with this situation exactly, and I don't know
> anyone who does ... but seriously think the
> difference in torque will be barely measurable.

While I don't exactly drive electric cars, I have used this dual motor 
design using e-bike parts on some large load-hauling work-trikes.

I have two vehicles that used paired rear wheel hub motors, and they 
balance out just fine with no evident pull to one side.  The pair of 
motors can also propel a vehicle through a very tight turn smoothly.  I 
suspect this is a good way to go, so long as the motors can be mounted 
firmly to the chassis.  If space near the old engine mount permits then 
a pair of reduction gears could be mounted up there as well, letting you 
increase the size of the chainring at the motor.

I might suggest using a separate controller for each motor, biasing the 
throttle input between them for differential control, if you wish.  I 
don't bother with this such biasing, but then my stuff all tops out 
around 20 mph.

> You may at least want a lower gear ratio than 3:1.  Assuming a 20" tire
> on a compact car, that gives you a 120mph top speed at 6000rpm...

As to the one-speededness of the vehicle, that may be a good thing in 
the big picture.  Why does anything really need to go faster than 
30-35mph anyway, aside from habits imposed by the bad old way of doing 
things?  While EVs are a great solution to the pollution being produced 
in cities, the underlying problem of energy consumption, as well as the 
oft-neglected matter of public safety, is mainly addressed by driving 
vehicles slower.

-- 
Mike Librik, LCI #929
Easy Street Recumbents
Austin, TX
(512) 453-0438
www.easystreetrecumbents.com