Lithium ion batteries (Li-ion) should not be stored for long periods of time, either uncharged or fully charged. The best storage method is to store them at a low temperature, not below 32°F, at 40-50% capacity. Storage at 41°F to 50°F is ideal. Since lithium batteries self-discharge, it is recommended that they must be recharged and used again until drained to 40-50%, every 6 months.