This information was obtained from the Panasonic Sealed Lead Acid Batteries Technical Handbook, 1998-1999 It applies to most sealed lead acid batteries.

Storage of batteries

(1) Store the battery in a stable position so as to keep the terminals of the battery away from any metallic or other conductive material (including items that may fall or drop onto the battery).

(2) Protect the battery from rain. If the terminals of the battery come into contact with water, they may be corroded.

(3) As a general rule, the battery should be stored in it's upright position, but it can be used in any position when placed in it's device. Do not apply abnormally strong vibrations or shocks to the battery. Transportation of the battery in an abnormal position or the application of abnormally strong vibrations or shocks to the battery may cause damage to the battery and the deterioration of characteristics.

(4) Batteries should be stored at room temperature and never exposed to extreme heat or cold conditions.

Recommendations

(1) During storage of the battery, it must be charged at least once every 60 days. If the battery has been stored for a long period in a discharged state, it may not be able to regain it's capacity even if it is recharged.

(2) If the battery is stored for 2 months or longer without being charged, its service life may be shortened or may completely fail.

(3) Store the battery after fully charging it, otherwise its service life may be shortened.

(4) Use the battery as soon as possible. The battery gradually deteriorates during storage and thus its decreased capacity may be irreversible even allowing for recharging.