[Oeva-list] newbie questions

Graunke, Gary gary.graunke at intel.com
Tue Apr 22 14:40:10 PDT 2008


So this is a bit complicated to explain on the list. I recommend Bob
Brandt's book: Build your own electric vehicle. 

Short answers: 
Distance is determined by the amount of energy and the rate at which you
use it up (slower uses less energy for the same distance). The energy is
in kilo-watt hours, and is the product of the battery capcity
(amp-hours) and voltage. 

Speed is only limited by much power (energy delivered per time) in
kilo-watts your motor, controller, and batteries can deliver. You can
keep going faster until the energy needed to maintain that speed matches
what you can deliver. 

Acceleration is also limited by power. Higher voltages can increase your
power, but the energy per pound of batteries is the same regardless of
voltage. You can go faster but run out sooner (see first answer).

Taking off limiters will let you go faster, but at the expense of
distance.

The energy needed grows with the cube of the air speed, and is the
dominant energy sink above 40 mph (the other factor being rolling
resistance). So your miles-per-KWH is reduced as the square of the air
speed at high speeds. This is true for gas cars as well... See Bob's
book.

Gary  

-----Original Message-----
From: oeva-list-bounces at oeva.org [mailto:oeva-list-bounces at oeva.org] On
Behalf Of Janet Redhawk
Sent: Tuesday, April 22, 2008 2:19 PM
To: OEVA
Subject: [Oeva-list] newbie questions

Hey,

I'm still waiting for box on conversion to arrive so
sorry if these are questions that would be covered
there.

I know this is a complicated questions but if someone
could give me the 10000 foot over view that would be
great.

How is distance and speed determined?  Is it a
combination of the engine and batteries?

I keep hearing owners of off the shelf EV's saying
they took off the "limiters" on their new vehicles so
they could go faster or longer.  Would it be possible
to do that and put more batts in to make it go
fast/longer?

thanks

J


 
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