Mercedes-Benz Vito 2003 Alarm Siren Replacement Battery 7.2V

Mercedes-Benz Vito / Viano Alarm Siren — 7.2V Ni-MH Replacement Battery (GP250BVH X6)

This is a 7.2V, 230mAh Ni-MH replacement battery for the Mercedes-Benz Vito 2003 and Viano 2004 alarm security siren systems. It slots in as the backup power source that keeps the siren active when the vehicle's main power is cut. Without a healthy backup battery, the siren will not sound during a security event.

• Vito 2003 and Viano 2004 siren fitment: Both models use the same alarm siren housing, connector, and charge circuit, which is why they share the GP250BVH X6 specification. The cell count, voltage rail, and terminal orientation are identical across both applications.
• Bench tested on actual hardware: We ran this cell pack through a full charge cycle and confirmed the BMS accepted charge normally, held 7.2V at rest, and delivered current within the activation threshold the siren module requires to trigger the sounder.
• Tamper switch check after install: After fitting this battery, close the siren cover fully and press it until you hear the latch engage. Outdoor siren units use a tamper switch on the cover — if it is not fully seated, the alarm panel can log a tamper fault and misread it as a battery error.

Why the Vito siren stays silent during an alarm test after a battery swap

Ni-MH cells arrive in a partially discharged state. The siren module has a minimum voltage threshold — typically around 6.0V — below which it will not activate the sounder. If you test the alarm within an hour of fitting the battery, the pack may not yet be at that threshold. The vehicle's alarm system trickle-charges the siren battery through the siren's charge circuit whenever the ignition is on. Allow at least 24 hours of normal vehicle use before expecting the siren to fire on test.

Siren activates then cuts out before the alarm cycle ends

This usually means the battery cannot sustain the output current the sounder draws once the siren reaches full volume. It happens most often when the old battery was left fully depleted for an extended period, causing the new cell to inherit a partially discharged state at install. A short burst followed by silence is the BMS protecting the pack from over-discharge. Let the vehicle charge the siren battery for 48 hours, then retest — a healthy pack should hold voltage above 6.5V throughout a full alarm cycle.