Your article "A new spin on electric-car batteries" (Developments to Watch, July 13) needs some clarification.
We project that AFS flywheel batteries, if installed in General Motors' two-passenger Impact electric car, would propel it between 300 to 600 miles per charge, depending on the fiber composite used in the flywheel rotors. Twenty AFS flywheel batteries would fit into the present battery channel of the Impact and could store 43.6 kilowatt hours of energy--enough to drive the Impact 400 miles, roughly four times the 80- to 120-mile range with the car's current 32 lead-acid batteries. If the Impact were reconfigured so that a total of 32 AFS flywheel batteries could be placed in the vehicle, it could go up to 600 miles on one charge. Or, instead of increasing the range, flywheel batteries could be added to increase the payload, so that, for example, it might be possible for GM to build a viable four-passenger Impact.
Edward W. Furia
American Flywheel Systems