All Ultralife lithium batteries, regardless of type, must be stored in a cool, dry environment in as close as possible to room temperature. This is the best practice to assure battery charge retention and shelf-life. While in many cases the specified storage temperature range is wider than just close to room temperature, best practice is to stay between 15 and 25 centigrade (59 to 77 Fahrenheit). Storing lithium batteries at significantly hotter temperatures, especially above 65°C (149°F), has the unwanted effect of breaking down the solvent, dissolving cathode atoms into the electrolyte, and any moisture present in the cells begins to react with the lithium – all of which degrade both the shelf-life of the battery and, in the case of rechargeable batteries, their charge retention.
While storing the battery at significantly colder temperatures has the benefit of reducing the battery’s rate of self-discharge, it has the unintended effect of raising the relative humidity of the air increasing potential of condensation and possibly corrosion. While lithium metal batteries (primary) can be stored at any state-of-charge, lithium ion batteries (rechargeable) must be stored at a state-of-charge that is between 40 and 60%. This ensures that the battery will have enough charge to allow for an adequate amount of storage prior to becoming severely depleted and precludes any breakdown of electrolyte that begins to occur whenever a cell’s voltage is within its upper voltage range.
Lithium ion batteries should be recharged back to a 40-60% state-of-charge once every four to six months following the charging recommendations of the manufacturer.
