Today's best lead acid batteries hold about 35 watt-hours (WH) per Kilogram (Kg) of battery weight. The current Metal Hydride (EV+) batteries hold about 70 WH per Kg (about twice as much). Thus we can calculate that our car, with about 26.2 total kilowatt-hours (KWH) of "fuel", has a battery pack that weighs 26,200 WH divided by 70 Kg, or 374 Kg, (843 pounds). Our car and its battery pack are experimental, so the numbers are approximations. Better batteries store more energy and weigh less.
Zinc-Air batteries (in use by Electric Fuel Corporation, at up to 150 KWH of energy) hold about 180-240 WH per Kg. Lithium Ion/polymer, under development by Valence Technology and many others, hold from 90 to 200 WH per Kg.
Thus, the Honda EV+ batteries hold about twice the energy as the EV1, pound-for-pound, and Electric Fuel's Zinc-air batteries have about two to three times the capacity of the Honda EV+ battery by weight.
| Battery type |
KWh per Kilogram |
Total KWh for a battery pack weighing 374 kilos, or 843 lbs. |
Distance our Honda EV+ would be able to travel if our 374 kilos of battery were of each type |
| Lead Acid | .035 | 13 | 59 miles (note that the EV1 lead battery-- 1,200 lbs--is heavier and holds more energy than this) |
| Metal Hydride | .070 | 26.2 | 120 miles, or 4.5 miles per KWh (estimated figure for "nominal" drving and full discharge) |
| Zinc-air | .21 | 80 | 360 miles (The Champ!) |
| Lithium Ion/Polymer | .15 | 56.1 | 252 miles (not yet available) |
(Numbers due to Resident Engineer, any errors are mine)
Of course, there are other considerations. Zinc air requires a battery exchange program, with the batteries regenerated at a central recharging station. This may be a big advantage since we would not have to wait for the battery to recharge at the exchange stations, and it could be recharged/rebuilt during off-peak hours. Zinc-air batteries would enable electric school busses to run 250 miles on a single charge, enough to run all week or for typical field trips. |
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