Re: Batteries - EV Conversion

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

On 3/1/2025 2:23 PM, bp@www.zefox.net wrote:
 

I asked one of my drive suppliers if an industrial high voltage inverter
could be used for an EV controller.  Polyspede makes them rated upto
500HP and input voltage from 380-480.  A regenerative 200HP Polyspede
sells for about 4 grand.  For the bigger ones the price jumps quickly.
One rated at 400HP is almost 10 grand.

 
Those horsepower numbers seem exceedingly large. Is it really required?
I'm thinking in terms of 100hp peak, 20hp continuous at most. It
might require a multi-speed transmission, but that's key to efficiency
anyway. Am I overlooking something? A 12 kg LiFePO4 battery can deliver
about a kilowatt for a minute or so. Do you really want 250 of them?

 
Well, we are talking about a full size pickup truck in my case.  Like I
said if we were looking at a gen 1 Miata or a Chevy Luv we could get by
with the readily available 90HP 144 volt system.  Might even feel peppy
with the fact that electric motors start putting out near full torque
from a relatively low RPM.  When you look at working vehicles things
change a bit.  Even my S-10 pickup developed around 200HP (190ish if I
recall) with its 4.3L V6.  At even 120HP of the Sonoma I had before the
S-10 with its 4 banger it was a dog.  It would do freeway speed... down
hill with a tail wind.  LOL.
 
 
An extended cab Ram 1500 is going to be around 5000lbs.  Maybe heavier
with batteries. Motor is lighter with EV but batteries take that back.

Almost certainly much heavier. LiFePO4 commondity batteries that can
deliver 200 mechanical horsepower are going to weigh close to a ton.
Lithium-cobalt and variants will be considerably less massive but
more expensive, more fragile and more destructive if they fail badly.

Now I don't need highway speed, but there is no real torque benefit to
lots of gears.  Not much anyway.  Most EVs drive in 1 or 2 gears.  I
think most just have a single speed gear box.  They do not even have a
shiftable gear box since you don't need gears for reverse. 

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.

 
When you get into full size pickup trucks I am thinking 160-200HP is
about the minimum for hauling a load and accelerating at a reasonable
rate even if you never drive over 55.  I am aware that Chevy put the
4.3L out of the S-10 in a full size truck.  That was really pushing the
minimum limit for a full size truck in my opinion.  Still I think that
HP range is the minimum for a full size.  Electrics have "some" torque
advantages, but not enough to make up a severe lack of power.
 
For comparisons, all of my gas and diesel 3/4 ton trucks have developed
over 300HP, and my current one supposedly bumps over 400HP.  I don't
think 200ish is unreasonable for a full size half ton extended cab.  I
mentioned that industrial inverters are available in larger sizes for
reference, and because larger electric EV motors are readily available,
and not oversized for their applications.
 
My real insight though was, "What if we could use industrial motor
inverters instead of auto industry proprietary distribution inverters?"

Clearly you can, but now that I understand your performance desires
the project is going to be pricey indeed. It isn't unreasonable to
_want_ 200 horsepower in an EV, but as you've discovered it's expensive. 
The project isn't impossible, but it's cost ineffective and likely to
remain so for the foreseeable future. Silly styling aside, a Tesla
Cybertruck is close to the best-performing EV truck possible now.
I'd be curious to know how it compares to what you're looking for.
Or maybe the Ford F150 Lighting.

bob prohaska