It is not the motor asking for a certain amount of electricity,
the setup: battery - controller - motor
places the motor in the dependent position, how much that the
*controller* allows to flow from the battery.
So, the short of it is that if the battery cannot deliver as much as the
motor could be taking, then it is the task of the controller that limits
the current (or voltage) to the motor. This means - *you* need to
program the controller to limit the output to the motor to a safe level
for both
motor and batteries.
NOTE that if the batteries are capable of delivering more power than the

motor can handle, again it is the controller that regulates a safe
amount to be delivered, though the controller can be setup to deliver an
instantaneous large amount and throttle back to avoid overheating or
otherwise damaging the motor.

Direct Drive tends to "lug" the motor, meaning: low RPM and high torque.
Torque is produced from current through the motor.

NOTE that for high motor current, it is not required that the batteries
are capable of the same current, as the controller can "multiply"
current at lower output voltage, so the controller and motor must be
capable of handling high current for a direct drive setup, or else you
will be very disappointed by the result.

For example, if the motor is capable of "only" carrying a peak 1000A
while the voltage on the motor is always below 30V because it is running
at such low RPM, then there is no way to force the motor to deliver more
than 30kW
even though your battery pack may be 144V and 200kW!
Note that if you can put a 2:1 gearing between motor and shaft, your
current goes down 2x and voltage goes up 2x so that means 500A 60V, much
more reasonable!

If your motor allows a peak of 2000A and at the normal driving speeds
take aound 50V then you are already in the 100kW range, but now there
are very few controllers that can dish out 2000A, in fact I only know
one affordable version and it is the Zilla 2K which is a DC controller.
For direct drive it will likely need a pretty beefy DC motor, especially
the brush setup needs to survive the 2000A currents, but drag racers
have shown that it can be done. Forced cooling of the motor and brushes
is a must!

My previous EV was a US Electricar truck that was a factory converted
It retained the manual gearbox but there was no stick - the box was
permanently locked in 2nd gear as a fixed reduction, so that the entire
setup allowed the AC motor to spin faster, 1000 RPM for each 8 MPH.
The truck topped out at 72 MPH since the motor redline was 9k RPM.

I am guessing that the question is if you can place the electric motor
*before* the transmission?
Or find the highest reduction diff for your Mustang that you can find,
you need to keep the Revs up to keep the electric motor alive!

Another alternative would be to place the electric motor next to the
drive shaft with a sprocket on the motor axle pointing forward (next to
the output from the transmission) and a 4x larger sprocket on the
transmission output.
That 4x reduction from the motor will allow you to spin the motor at a
decent RPM because the drive shaft typically does around 1k RPM at
freeway speed, so your motor is then doing 4,000 RPM. If that reductoin
is built-in to the motor, all the better.


Cor van de Water
Chief Scientist
Proxim Wireless Corporation
Email: Private:
Skype: cor_van_de_water Tel: +1 408 383 7626

-----Original Message-----
From: Ben Goren [] 
Sent: Friday, July 25, 2014 4:21 PM
To: Cor van de Water; Electric Vehicle Discussion List
Subject: Re: [EVDL] Hybrid Mustang: batteries

On Jul 25, 2014, at 3:21 PM, Cor van de Water via EV <>

> Why on the world would you need over 200kW unless you are doing a race
> car?

Well, each AC-51 is rated for ~80 kW; I'm assuming a pair is ~160 kW --
which is about the same as the 260 motor in the car already. Seemed to
me that that it doesn't make sense to have the motor(s) wanting more
electricity than the batteries can deliver, so I've been trying to reach
at least 180 kW...but maybe that's not the way I should approach this?

Um...maybe I should back up again.

The only practical place to add an electric motor is along the
driveshaft, after the transmission and before the differential -- which
means a direct-drive setup. It's my understanding that that means lots
of electric motor to be able to live with the gear ratios, with a pair
of AC-51s or WarP 9s as the likely candidates. Based on that, I assumed
that the batteries would, in turn, have to supply as much electricity as
the motors could take -- else there wouldn't be a need for so much motor
in the first place.

> My suggestion: use half your pack size (are there 90 Ah cells that you
> can use instead of 3 strings of 60?) which gievs half the cost and
> capacity, as you indicated that is what you need.

See, this is why I'm bugging y'all. As many times I've been over the
various pages, I've often been looking for something different each
time, and I've apparently missed something yet again. <sigh />

No 90 Ah cells are leaping out at me with a quick search, but I now see
CALB 70 Ah 10C cells for $80.40 here:

Two strings of 45 gets 200 kW with 20 kWh at 500 pounds for $3900 --
something *much* more reasonable than anything I had calculated earlier.

So...maybe this isn't hopeless after all. Thanks!

...and now back to do yet still even more research....

For EV drag racing discussion, please use NEDRA 

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