About this replacement
Indexa OS360A / OS365A — 4.8V Ni-Cd Replacement Battery (AKKU-360A)
This is a 4.8V, 2000mAh Ni-Cd replacement battery for the Indexa OS360A and OS365A wireless alarm systems, along with compatible units including the 151A and 32094. It restores the backup power cell that keeps the alarm operational when mains power drops. OEM part numbers AKKU-360A and BAT4V8 both cross to this cell.
- OS360A / OS365A series compatibility: These models share the same 4.8V four-cell Ni-Cd pack configuration, connector pinout, and charge management circuit. Swapping between OS360A and OS365A units uses the same physical cell — the panel BMS reads charge state identically across the range.
- Bench tested on actual hardware: We cycled this cell through charge and discharge on a Ni-Cd test rig, confirmed the BMS accepted the pack without fault codes, and verified the cell voltage held above 4.2V under load before shipping.
- Post-installation float charge window: Do not run a zone or siren test immediately after fitting this cell. Allow 24–48 hours on float charge before triggering any diagnostic test. A freshly installed Ni-Cd pack will sit below the panel's low-battery threshold until the first full charge cycle completes.
Alarm panel showing low battery hours after installing new cell
The OS360A panel samples backup battery voltage against a fixed threshold — typically around 4.4V for a 4.8V Ni-Cd pack. A brand-new cell arrives partially discharged after storage and will read below that threshold until the panel's trickle charger brings it up. This is not a fault with the replacement cell. Leave the panel powered on mains for 24–48 hours and the low-battery warning will clear once the pack reaches full float voltage near 5.4–5.6V.
Alarm losing stored programming during a mains power outage after battery swap
If the panel loses zone programming or user codes during a power cut, the backup battery was not yet supplying enough voltage to sustain the memory circuit. The OS360A's memory hold voltage is lower than its alarm-trigger threshold, so the panel may appear to function normally on mains while the cell is still too flat to hold the board live. Condition the new cell for 48 hours on continuous mains power before testing backup operation. After that period, the pack should hold the panel above the memory retention voltage throughout a standard outage.