Re: 'Coming in on a Plate and Prayer'

["VanDerWal, Peter MSgt" <vanderwp@fhu.disa.mil>]

> > Being late at night (9 pm) does not mean there is less
> > traffic. But it was down hill most of the way. Instead of
> > starting in first and changing up to second at 15 mph, I
> > would start in second, and change up to third at 10 mph.
> > This shifting up early worked well for me.
>
> Now, that is very odd! In every DC EV I've driven, shifting early makes
> the motor draw ~more~ current from the batteries, not less.
>

It depends on if your controller limits motor current or not.  Shifting up
will make the motor draw more current but at a lower voltage.  If your
controller is in motor current limit, shifting up won't change the motor
current (controller limits it) but will lower the motor voltage which means
less power (and slower acceleration).

On the battery side of the controller less power equates to lower current.

The GE controller in my truck limits motor current to about 550 amps, when
the batteries are cold I shift up just as they hit 105V (120V pack).
Shifting up causes the motor to slow down and my pack voltage climbs to 110V
or so and then starts down again as motor voltage climbs and battery current
climbs with it.

Acceleration is slow but it's much easier than trying to modulate the
throttle to keep battery voltage right at 105V (that requires millimeter
precision on my truck)