The only exceptions regarding the recommended charge level for long term storage are the lithium-ion based PowerUnit and LiveAmp batteries. Storing a lithium-ion battery is recommended at a 30 % – 80 % charge level. For longer storage periods without regular recharge, the battery should begin the storage at an 80 % charge level. For practical purposes, an 80 % charge level can be reached by first loading the battery to 100 % and then using it for a 2 hour (PowerUnit) / 1 hour (LiveAmp) recording before storing it.
To keep PowerUnit and LiveAmp batteries fresh and fit, they should run through a charging/discharging cycle at least once every 4 – 8 weeks. In an optimal cycle they should be discharged to approximately 30 % charge levels and charged again to 80 % and then stored again. For practical purposes, an approximate 30 % charge can be achieved by using a fully charged battery for 70 % of the maximum operating time. E.g., to drain a new battery from 100 % to 30 % you would need approximately 11 hours of recording for the PowerUnit and 3 hours for the LiveAmp. Please note, that this maximum operating time can diminish as the battery gets older, so the time to get to 30 % charge also diminishes.