Physio-Control Lifepak 9 Replacement Battery 16V 2500mAh

Physio-Control Lifepak 9 Series — 16V Sealed Lead Acid Replacement Battery (803704-03)

This is a 16V, 2500mAh sealed lead-acid replacement battery for the Physio-Control Lifepak 9, 9A, 9B, and 9P portable defibrillators. It replaces OEM part numbers 803704-03 and 21300-002259. Voltage and capacity match the original specification from the product data.

• Lifepak 9 series compatibility: The 9, 9A, 9B, and 9P share the same 16V battery rail, connector footprint, and BMS handshake protocol. One battery covers all four variants without modification.
• Bench tested on actual hardware: We cycled this battery through a charge-discharge sequence and monitored the BMS handshake at startup. The self-test completed cleanly and the charge IC accepted the cell without flagging a chemistry mismatch.
• Post-installation self-test protocol: After swapping this battery in, let the Lifepak 9 complete its full power-on self-test without interruption. The BMS runs a verification sequence at startup — cutting power mid-cycle triggers a false battery fault that latches until the next clean reboot.

Why the Lifepak 9 fails its self-test after a battery swap

The Lifepak 9 runs an internal self-test at every power-on that checks battery voltage against a stored threshold. A freshly installed sealed lead-acid cell that has not completed one full charge-discharge cycle may sit at a resting voltage that falls just short of that threshold. The BMS has no way to distinguish a partially charged new cell from a degraded old one — it reads voltage, not cycle history. Run one complete charge before placing the unit back in service, and the self-test will pass on the next boot.

Charge indicator not reaching 100% on the first charge after replacement

This is normal behaviour for a new sealed lead-acid cell on its first charge cycle. The charge IC in the Lifepak 9 applies a conservative current limit when it does not recognise a cell with an established charge history, which causes the indicator to plateau before reaching the full-charge state. The cell needs one complete charge-discharge cycle before the charge IC recalibrates its endpoint. After that first full cycle, the indicator should reach 100% and hold there at a resting voltage of approximately 13.5–13.8V open circuit.