Wheelchair batteries: driving cycles and testing.

The battery performance of electric wheelchairs was measured under indoor and outdoor conditions, and simulated driving cycles for these two environments were derived from these tests. Driving cycles were used to bench-test deep discharge wet cell and gel cell lead-acid batteries, nickel-cadmium batteries, and experimental nickel-zinc batteries. Results of this study support the conclusion that deep discharge wet cell lead-acid batteries satisfy wheelchair requirements and are the most economical choice. The effect of simulated wheelchair controller pulse width modulation on battery discharge compared to d.c. discharge was found to be negligible. A simple model analogous to Miner's Rule (3) plus results plotted on a Ragone chart of average power versus discharge time were found to correlate the effect of the highly variable actual power requirements of an electric wheelchair. Miner's Rule can predict battery performance for a given driving cycle.