Dead or weak standby batteries are the single most common failed-inspection item we hear about. Here is what actually matters when it comes time to replace them.
What NFPA 72 requires
NFPA 72 requires standby and alarm capacity testing on every panel. This matters because a battery can read the right voltage sitting idle and still fail to carry the alarm load when the panel actually needs it. A quick voltage check is not the same as a capacity test.
The practical replacement interval
As a rule of thumb, most sealed lead-acid (SLA) standby batteries are replaced about every five years. Any battery past that age is a punch-list item waiting to happen — it is cheaper to replace it on your schedule than on the inspector’s. For more on why battery quality matters, see The Importance of Quality Batteries in Commercial Fire Alarm Systems.
Getting the size right
The battery has to cover the panel’s calculated standby load plus alarm load. Undersizing is a common cause of trouble signals and failed capacity tests. The three sizes that cover most commercial panels are 12V 7Ah, 12V 18Ah, and 12V 33Ah. When in doubt, match what is printed on the battery you are pulling out.
Need batteries before your inspection?
We stock 12V 7Ah, 18Ah, and 33Ah SLA batteries sized for the major panel brands. Shop fire alarm replacement batteries or contact us and we will make sure you have the right size before the inspector shows up. Not sure what else your inspection will flag? Read the most common fire alarm inspection failures.
