About this replacement
HeartStation Premium Alarmed Cabinet — 12V Li-MnO2 Replacement Battery (M902)
This is a 12V, 1350mAh lithium-manganese dioxide battery that replaces the M902 backup cell in the HeartStation Premium Alarmed Cabinet. It fits the Premium Alarmed Cabinet, RC2000R, RC2000W, and RC5000R. This cell powers the alarm circuit during mains outages, keeping temperature and integrity monitoring active when grid power drops.
- RC2000R, RC2000W, RC5000R compatibility: These models share the same 12V alarm bus and M902 connector footprint. The BMS handshake expects Li-MnO2 chemistry at this voltage rail — substituting a different chemistry will trigger a persistent alarm fault even at full charge.
- Bench tested on actual hardware: We ran this cell through the M902 circuit under simulated mains-loss conditions. The BMS completed its verification sequence without fault flags, and the alarm circuit held steady through the full discharge profile.
- Post-installation self-test protocol: After fitting this cell, do not interrupt the cabinet's power-on self-test cycle. The BMS runs a chemistry verification at startup — cutting power during this window logs a false battery fault that persists until the next clean reboot, which can affect compliance records.
Cabinet alarming low battery with a freshly installed M902 cell
The HeartStation alarm circuit uses a BMS threshold calibrated to the OEM cell's charge signature. A new Li-MnO2 cell fresh from packaging sits at a resting voltage that the BMS may read as below threshold on first contact — this is a calibration gap, not a faulty cell. Run one full charge cycle uninterrupted before drawing any conclusion. After that cycle, the BMS updates its reference point and the low-battery alarm clears. If the alarm persists past the second full charge, measure the cell terminal voltage — it should read at or above 12V under no load.
Cabinet fails to power on after the M902 cell sat in storage
Li-MnO2 cells self-discharge slowly in storage, but if the cell voltage drops below the BMS recovery threshold — typically around 10V on a 12V circuit — the BMS locks out and will not initialise. The cabinet appears completely dead even when mains power is connected. Connect the cabinet to mains and leave it on charge for a minimum of 24 hours without cycling power. This allows the charge IC to trickle the cell back above the recovery threshold before the BMS attempts a full handshake. If the cabinet still does not respond after 24 hours on mains, measure cell voltage directly — below 9V indicates the cell is below recoverable range.