Stationary batteries are intended to be purchased, shipped, received, installed and commissioned in a reasonable amount of time; generally 4 to 6 months, depending on the specific type. They certainly can be stored if there is an installation delay, but for a finite period of time before problems will develop for the user.
Lead-acid batteries are shipped from the factory fully charged. That said, during storage, they lose some of their charge which is expected and acceptable within limits set by the battery manufacturer. When stored for extended periods of time, and when coupled with higher than recommended temperature, their state of charge can easily fall below that recommended by the manufacturer.
After extended periods and especially at higher than normal temperature, commissioning the new battery system will become problematic due to low state of charge. Typical commissioning charge processes and procedures outlined in user manuals may not be adequate to get the battery Increased storage temperature increases the rate of self-discharge, also known as local action or standing loss. If an acceptance test is part of system commissioning, demonstrated capacity may be well below expectations.
Extremely low state of charge is to be avoided as irreparable damage to the battery can occur to the point where it cannot be recovered. The warranty is voided as a result and a new battery is required. Congratulations, you have a gigantic set of paper weights.
So, how long can batteries be safely stored? Well, that depends; a reply you'll hear from even the most seasoned battery person. Time and temperature are the key criteria. The specific manufacturer user manual should be consulted for this information.
Today's blog will provide some basic guidelines. Vented lead-acid (VLA) batteries using calcium grids can be stored for about 6 months from date of shipment at a temperature ranging from 65-85 degrees, F. VLA lead-antimony batteries experience a higher rate of self discharge for the same temperature, so their storage limitation is typically 3 months from date of shipment. VLA selenium batteries can be typically stored for no longer than 3 months providing the storage temperature has not exceeded 95 degrees, F.
Valve regulated (VRLA) battery storage times are slightly different but a guideline for these is 6 months maximum from 50-77 degrees, F. and it is reduced to 3 months when storage temperature rises to 78-92 degrees, F.
In all cases, it is vitally important that a new battery system be given a commissioning or freshening charge before being placed into final service and when an acceptance capacity test is part of the sign-off process.