(ET) Batteries and range -- 8 volt vs. 6 volt

["David Roden (Akron OH USA)" <roden ald net>]

> My plan is to use 6 eight volt Trojan T-875 golf cart (special Club Car
> design) batteries for a 48v pack in my E20.  This will sacrifice some
> range - roughly proportional to the voltage change - for higher power to
> the main drive - roughly proportional to the voltage increase squared or
> around 70% more power.

Actually, the range loss is not that bad.  Unless you use that extra 
power routinely, you shouldn't see a 33% difference in range.  The reason 
is that there's not that much difference in watt-hours of energy in the 
pack.

Look at the numbers.

A T-105, which weighs 62 lb, is rated 115 minutes at 75 amps, or 143 amp
hours at 75 amps.  At 6 volts (average), this is 860 watt-hours.

A T-875, with about the same amount of lead at 63 lb, is rated 75 minutes
at 75 amps, or 94 amp hours at 75 amps.  At 8 volts, this is 750 watt
hours.  

The difference is less than 13%.

In general, an EV's range is roughly proportional to the amount of 
battery weight; the voltage is not so important.


David Roden - Akron, Ohio, USA
1991 Solectria Force 144vac
1991 Ford Escort Green/EV 128vdc
1979 General Engines ElectroPed 24vdc
1974 Honda Civic EV 96vdc
1970 GE Elec-trak E15 36vdc