Batteries have been the weak link of electric vehicles for well over a century, so any development is of great interest. One bit of recent news was very exciting: Altair Nanomaterials announced a new anode material for lithium-ion (Li-ion) batteries which triples their current capacity and drastically shortens the necessary charging time. The implications for EV and HEV use is obvious: more power and better regenerative braking from the same battery pack.
According to certain authorities, the average commuter travels 22 miles a day or less; this means that a car which can travel 22 miles on electric power alone can eliminate these people's fuel requirements for work travel, and cut total fuel needs by as much as 80%. Longer all-electric range translates to less fuel use.
According to EPRI, a compact electric vehicle would require about 250 watt-hours per mile of range (it is not clear if this is measured at the charger input, the charger output, or between the batteries and the motor). Others differ; AC Propulsion claims 205 Wh/mile for their tzero (presumably as output from the batteries), while Commuter Cars says a Tango would need about 180 Wh/mile. For a slightly larger vehicle, the EPRI figure 250 Wh/mile seems to be reasonable for a BOTE analysis.
Range is the other figure. 30 miles is well over the average commute, and would certainly capture the 80% reduction in fuel requirements projected by analyses which find 22 miles is sufficient. To obtain 30 miles range at 250 Wh/mile and 80% discharge, a battery would require a capacity of 30 * 0.250 / .8 = 9.375 KWh; call it 10 KWh even, for simplicity's sake.
The last element is power. To meet consumer demands, a car will probably need at least 100 horsepower, perhaps 150 horsepower. This means that the battery must be able to supply 75 to 112 kilowatts of power for acceleration.
For batteries, I like to look at batteryspace.com. Their best Li-ion offering at the moment is a pack of 50 cells in the 18650 configuration (18 mm diameter by 65 mm long), which store 2000 milliamp-hours (2 amp-hours) at 3.6 volts nominal; for this they're asking roughly $5.00/cell. The 50-pack is specified at 81 ounces, or roughly 45.6 grams/cell. The specifications say that they are limited to a 2.5 C (5 amp) discharge rate. Suppose that Altair's electrode technology can triple this to 7.5 C; at that rate, a 10 kWh battery would be able to supply 75 kWpeak, nearly as much as a typical NiMH battery.
For NiMH, the cost leader is a 10-pack of C cells, 4500 mAH at 1.2
volts nominal for $3.30/cell. Assuming a 10 C discharge rate, a
10 kWh pack would be able to supply 100 kWpeak.
I chose to assume two different configurations: a commuter car with 75 kW (100 HP) of power, and a sport model with 112 kW (150 HP) of power, with 30 miles minimum all-electric range at 100% discharge. My calculations came out like this:
| Electric range, mi
||Commuter, 75 kW||7.5||126||$4583||30
|Sport, 112 kW||11.2||188||$6844
||Commuter, 75 kW||10||63.8||$6944
|Sport, 112 kW||14.93||94.3||$10370
What can we expect in the future?
Visits since 2006/05/11: