Depending on the ambient temperature, batteries naturally self-discharge 1% to 25% per month while in storage, and lead sulphation will start occurring when the state-of-charge drops below 100%. If left in a vehicle, disconnecting the negative cable will reduce the level of discharge by eliminating the parasitic load. Cold will slow the self-discharge process down and heat will speed it up. Use the following six simple steps to store your batteries:

  1. Physically inspect for damaged cases, remove any corrosion, and clean and dry the battery tops.
  2. Fully charge and equalize, if required, using the procedures in Section 8.
  3. Check the electrolyte levels and add distilled water as required, but avoid overfilling.
  4. Store in a cool dry place, but not so that it will freeze. The freezing point of a battery is determined by the State-of-Charge and the higher it is, the lower the freezing temperature. Based on the battery type you are using, connect a "smart" microprocessor based three stage or four stage charger or a voltage regulated float charger to continuously "float" charge your battery. Do not use a cheap, unregulated "trickle" charger or a manual two stage charger which was not designed for float charging or you will over charge your battery.
  5. A less desirable alternative to float recharging would be to periodically test the State-of-Charge using the procedure in Section 3. When it is 80% or below, recharge using the procedures in Section 6. The frequency of testing and recharging will depend on the ambient storage temperature.
  6. When you remove the batteries from storage, equalize wet (flooded) or AGM batteries, if required, using the procedure in Section 6.