Because a rechargeable battery has an increased number of uses (e.g., cycles), the battery's internal impedance can increase and the efficiency of the battery can become degraded. This internal resistance can cause cutoff voltage thresholds and cutoff current thresholds to prematurely stop a phase of battery charging, as these cutoff values can be based on low-cycle count batteries. New cutoff values can, instead, be based on battery impedance. Use of an adjusted cutoff current threshold during a constant voltage cycle can increase the capacity of high-cycle count batteries. Use of an adjusted cutoff voltage threshold in step charging can increase the charging speed of high-cycle count batteries. These increases in efficiency by using adjusted cutoff values can increase as the battery is further high-cycle count, in comparison with low-cycle count cutoff values used with high-cycle count batteries.