The life-span of rechargeable batteries is affected by many parameters. Some of which are within our control, being mainly proper charging. Chargers that overcharge cause excessive heating and internal gassing that can shorten battery life. Chargers that undercharge leave the battery susceptible to cell imbalance and sulfating. Proper discharging is important to minimize voltage depression and maximize the cyclic use of the battery. Operation in elevated temperature environments is stressful on rechargeable batteries and will result in shortened cyclic and calendar life spans.
Storage – For best results all batteries should be stored in a cool dry place
Lead acid batteries should be stored fully charged and free of moisture and dirt between the terminals to help prevent self discharge and sulfating.
Lithium-ion batteries should be stored charged, or partially discharged (25-50%), in a cool dry area.
Nickel Cadmium and Nickel Metal Hydride batteries can be stored fully charged or discharged at temperatures of between -20 and 30 degrees Celsius for almost an indefinite period of time without suffering any loss in capacity. For safety reasons it might be better to store them discharged, but be sure to completely disconnect them from there load so there is no prolonged current drain. Even a small load will eventually bring the output voltage to zero and cause the cells to leak electrolyte. After long periods of storage the battery may resist charging at first, but a good charger or analyzer should be able to bring them back up to full capacity within a few cycles with no trouble.