Re: Batteries - EV Conversion

Bob La Londe <none@none.com99> wrote:

On 3/1/2025 5:52 PM, bp@www.zefox.net wrote:

EVs benefit from a shiftable transmission exactly the way IC vehicles
do. The transmission minimizes current draw when torque is needed and
minimizes voltage required when speed is needed. Their omission is a
matter of cost control, not design optimization. The only thing they
don't need is a clutch. The current minimzation is especially important,
because electrical efficiency is inversely proportional to the square
of the current draw.

 
You are right of course.  Maybe not exactly, but the principal is
certainly still true.  I would not be a fan of dropping an EV motor in
front of a Dodge automatic transmission.  I'm not even sure it would
operate without being hooked to the Dodge computer.
 

Somebody would have to cook up a "PCM simulator" to generate the
signals (likely digital) needed by the transmission. Not a trivial
project in itself. But, it would increase low-speed acceleration
by an amount roughly equal to the gear ratios for a given battery
power. IIRC older Dodge 46RH and RE used a 2.45:1 low gear, which
would certainly be a noticeable improvement off the line. The torque
converter could be kept locked at all times if desired, but it would
probably be simpler to let it unlock while shifting. 

As you observed elsewhere, batteries are a more fundamental problem.
At energy/power densities approaching hydrocarbon fuels they take on
the character of rocket propellants. There's no easy remedy for that
problem, which few people anticipated. I certainly didn't.

Thanks for a most entertaining discussion!

bob prohaska