A battery system can provide backup power for information technology (IT) equipment. In response to a lithium ion based battery being inactive (not charging or discharging), a temperature of the battery can be maintained at or below an optimal storage temperature of the battery, using a primary cooling system. If the primary cooling system is insufficient, the temperature can be maintained at or below the optimal storage temperature with a secondary cooling system that runs in addition to the primary system. The optimal storage temperature of the battery is determined based on an effort to cool the battery and a degradation of the battery.