[ausev] Fwd: Good sources to get started?

[Christopher Robison]

On Wed, 2007-11-28 at 09:34 -0600, Roy Holder wrote:
> another way to look at it:
> my car gets about 1 amp per mile per 1000 lbs at 120v in town.
> 2500 lb car, 150 ah batts(100 amps 1 hour rate) 120v = 40 niles
> 
> I have run the car at 96v, 108v and 120v for extended periods of time,
> kept a log of miles and amps, and calculated the energy use.

I hate to be pedantic, but I feel it's important to risk being a pest
especially for newcomers to understand the units we use.

Roy is referring to battery capacity and energy, and the units for these
respectively are amp-hours and watt-hours. Amps are a unit of electrical
current, and watts are a unit of power (flow of energy). 

"Amp-hours per mile" is one way to express this value, but you need the
pack voltage for it to be useful, as Roy has provided. In general it's
easier to quote watt-hours per mile instead which incorporates both
these values, and which is the standard in EV conversations. Assuming
100Ah and 120V, this gives a total of 12kWh in the pack. With a 40 mile
range this works out to 300Wh/mile, which is reasonable and in the
middle of the range you typically see (200-400). Of course it also
matches his first set of numbers, 2.5Ah/mile at 120V = 300Wh/mile.

I am curious about the stated 1-hour rate however. If accurate you're
definitely getting a lot more out of them than the usual calculation (20
hour advertised rate * .57) would suggest. Very cool if so; it may be
due to the non-continuous nature of driving...  (?)


-- 
Christopher Robison
chris at ohmbre.org
http://ohmbre.org          <-- 1999 Isuzu Hombre + Z2K + Warp13!