A charging energy control system includes an implantable medical device (IMD) and an external charger. The IMD receives charging energy to recharge a battery during a charging energy acceptance period and rejects the charging energy during an actual charging energy rejection period. The external charger transmits the charging energy to the IMD in order to recharge the battery. The external charger includes a charging controller configured to determine the actual charging energy rejection period, and regulate the charging energy during which the charging controller predicts a predicted charging energy rejection period of the IMD based on the actual recharging energy rejection period. The charging controller is configured to cease or reduce transmission of the charging energy during a charging energy conservation period that is at least a portion of the predicted charging energy rejection period.
