Batteries like cool temperatures and exercise. Try to keep batteries below 86°F (30°C). Exercise batteries with frequent charging and discharging (by using the device).
It’s better to partially charge electronics frequently than to fully charge and discharge. Partially discharging Li-ion is fine; they don’t have the same “memory effect” as older battery technologies, and they don’t need full periodic discharge cycles. The only reason to fully discharge and charge a battery is to calibrate the battery gauge, if the device has one.
Don’t leave batteries plugged in constantly, but don’t leave them empty for long periods either. If possible, turn devices off while charging to reduce battery stress. Laptops are a special case. Most laptop chargers will stop charging once the battery is full, and only start charging again when the battery is low. So, it’s generally unnecessary to disconnect a laptop from AC power once it’s charged.
Batteries should be stored in a dark, cool place. If storing for more than a few weeks, charge batteries to 30 – 60% (neither empty nor full). Use batteries once a month to exercise them.