VOLVO Compact Car Siren GP320BVH6A6 7.2V Ni-MH Battery

VOLVO Compact Car Siren — 7.2V Ni-MH Replacement Battery (GP320BVH6A6)

This is a 7.2V, 150mAh Ni-MH replacement battery for the VOLVO Compact Car Siren alarm sounder. It fits OEM part numbers GP320BVH6A6, N2H280, GP320BVHX6, and 6N280BC, covering siren units 8637399, 8622268, and 9452709 among others. The battery supplies backup power so the siren sounds even when main vehicle power is cut during a theft attempt.

• Compact Car Siren platform fit: These VOLVO siren units share the same 7.2V cell stack, connector footprint, and BMS handshake across the listed part numbers. Swapping to this battery requires no wiring changes — the charge circuit on the alarm module recognises the Ni-MH cell chemistry and trickle-charges at the correct rate.
• Bench tested on actual hardware: We cycled this battery through charge and discharge on a siren module, confirming the BMS accepted the cells without triggering a fault code. The siren output current draw was sustained without a mid-activation cutoff.
• Cover latch check after install: After fitting this battery, close the siren housing fully and confirm the tamper switch is physically engaged before leaving the vehicle. Outdoor siren units on VOLVO alarm systems report a tamper fault back to the alarm panel if the lid is not fully latched — some panels log this as a battery error rather than a tamper event, which sends the diagnosis in the wrong direction.

Why the Compact Car Siren activates briefly then cuts out mid-alarm

The VOLVO Compact Car Siren draws a short but sharp current spike the moment it activates. If the backup battery is partially discharged, its internal resistance climbs enough that the voltage sags below the siren's minimum operating threshold within seconds of activation. The BMS then trips the output to protect the cells, cutting the siren short. A fully charged battery at 7.2V nominal holds the output rail stable through the full alarm cycle. If the siren is cutting out, charge the unit for a full 24 hours via the vehicle's alarm system before testing again.

Siren battery voltage reading 7.2V but siren won't sound during alarm test

A resting voltage of 7.2V on a Ni-MH pack does not confirm the cells have enough charge to deliver current under load. Ni-MH cells hold a relatively flat discharge curve and can show near-nominal voltage while having very little usable capacity remaining. When the siren module demands current, the voltage collapses immediately and the unit won't activate. After fitting a new battery, allow the alarm system to trickle-charge it for at least 24 hours before running a test — check the open-circuit voltage reads above 8.0V before triggering the alarm.