SDG #033 Service Your Security Alarm Batteries!

Sealed lead acid batteries in intruder alarm panels are one of the most commonly neglected maintenance items in a building, and this repair shows exactly why that neglect gets expensive. The original Elmdene 12V battery backed supply had failed, but the root cause was not the electronics: an aged, high resistance SLA cell was pulling far more charging current than the supply was designed to deliver continuously, and the PSU eventually gave up trying to hold it at float voltage.

The replacement chosen is the Elmdene G13801N, part of the G1380xN family of boxed 13.8V supplies intended for alarm panels, access control and CCTV. These units are popular in the security trade because they combine a regulated float output, battery charging and low voltage cut off in a single enclosure with mounting space for the standby battery, so a like for like swap is usually straightforward. The wiring is simple, but the important detail is that the new supply is only as reliable as the battery hanging off it.

The practical lesson for anyone maintaining their own system is that alarm batteries are consumables, typically good for around three to five years, and they should be replaced on a schedule rather than left until the panel reports a fault. Checking terminal voltage under load, watching for case swelling, and confirming the charging current settles to a low trickle are all quick sanity checks. Doing that regularly avoids the situation documented here, where a cheap battery failure ends up destroying a much more costly power supply and leaving the alarm without any standby capability at all.