We report a method of recovering degraded lead-acid batteries using an on–off constant current charge and short–large discharge pulse method. When the increases in inner impedance are within ∼20% of the initial impedance value, their system will permit discharge times to recover to a level approximately matching their initial time values. In one experiment, when the discharge time of a <5-year-old lead-acid battery used for engine starting had degraded to about 50% of its initial discharge capacity, the authors found that 80% of the initial state discharge time could be recovered and maintained via their method. In a separate experiment, a deep-cycle battery was forcibly degraded by 12 h of depletion at a constant current of 10 A discharged at a terminal voltage of 10.2 V. The results of that experiment show that use of their on–off constant current charge method for the deep-cycle battery (recovered at 80% initial discharge time) quadrupled the post-recovery discharge time in comparison with a battery recovered via constant voltage charge. Taken together, these results indicate that use of their proposed on–off constant current charge system can successfully recover both degraded engine start and deep-cycle lead-acid batteries.