THE IMPORTANCE OF STORAGE CONDITIONS

The self-discharge rate of SLA batteries can be affected by the temperatures they are subjected to. Higher temperatures can expedite and cooler temperatures can decrease the self-discharge rate, but we recommend keeping our battery packs in an air-conditioned, 68-70˚F environment wherever possible.

In general, we discourage keeping battery packs in storage, but if you have to do so we recommend charging them every 3-6 months to maintain proper capacity, performance, and lifetime. Allowing an SLA battery pack to discharge below a certain voltage can damage it permanently.

Where necessary, we will be happy to work with you to manage delivery schedules to avoid possible self-discharge of the battery packs during your integration schedule.

BATTERY SHELF LIFE

In general, when lead acid batteries of any type are stored in a discharged condition for extended periods of time, lead sulfate is formed on the negative plates of the batteries.  This phenomenon s referred to as “sulfation”.

Since the lead sulfate acts as an insulator, it has a direct detrimental effect on charge acceptance.  The more advanced the sulfation, the lower the charge acceptance.

The table below shows the normal storage time or shelf life at various ambient temperatures.

Temperature Shelf Life
0°  C (  32° F) to 20° C (  68° F) 12 months
21° C (  70° F) to 30° C (  86° F) 9 months
31° C (  88° F) to 40° C ( 104° F) 5 months
41° C (106° F) to 50° C ( 122° F) 2.5 months

 

“Brief Usage”, ie., a few days, at temperatures higher than the ranges recommended, will have no adverse effect on storage time or service life.  However, if such use continues for more than one month, the storage time must be determined according to the new ambient temperature.

Top Charging

Since any battery loses capacity through self-discharge, it is recommended that a “top-charging” be applied to any battery which has been stored for a long period of time, prior to putting the battery into service.  Excepting conditions in which storage temperatures have been abnormally high, top charging is recommended within the following parameters:

Battery Age Top Charging Recommendations
Within 6 monthsafter manufacture 4 to 6 hours at constant current of 0.1CA, or 15 to 20 hours at constant voltage of 2.40 volts per cell.
Within 12 months after manufacture  8 to 10 hours at constant current of 0.1CA, or 20 to 24 hours at constant voltage of 2.40 volts per cell.

 

Recharging Stored Batteries

In general, to optimize performance and service life, it is recommended that NP batteries which are to be stored for extended periods of time be given a supplementary charge, commonly referred to as a “top charge”, periodically.

For additional questions, including more detailed explanations and information:

Additional, helpful information:

  • The MSDS for the batteries used in our popular SRNDT(I) Series UPS can be found here.
  • Navy Battery FAQ: A battery FAQ specifically written for UPS deployed shipboard in U.S. Navy and USCG applications