About this replacement
ResMed VS III — 24V Ni-MH Replacement Battery (88888455)
This 24V, 2000mAh (48Wh) Ni-MH battery replaces OEM part 88888455 in the ResMed VS III portable ventilator. It fits the VS III directly and matches the original voltage rail and connector configuration. Capacity figure is sourced from product data — 2000mAh at 24V nominal.
- VS III platform fit: The VS III runs a 24V bus with a BMS that validates cell chemistry and voltage signature at power-on. This replacement matches that voltage rail and connector pinout, so the device completes its startup handshake without throwing a battery fault.
- Bench tested on actual hardware: We cycled this cell through full charge and discharge on a VS III-class load profile. The BMS accepted the battery on first insertion, completed the self-test sequence, and the charge indicator tracked normally across the first three cycles.
- Post-swap startup protocol: After installing this battery, let the VS III complete its full power-on self-test without interruption. The device runs a BMS verification routine at startup — cutting power during this sequence triggers a false battery fault that persists until the next clean reboot.
Why the VS III alarms low battery immediately after a confirmed full charge
The VS III BMS stores a learned capacity profile from the previous cell. When a new battery is installed, the BMS compares its charge acceptance curve against that stored profile. A fresh Ni-MH cell charges differently in its first few cycles — the voltage rise comes slightly later, which the BMS can misread as insufficient charge. Run one full charge-discharge cycle before relying on the charge indicator. After that conditioning cycle, the BMS recalibrates its threshold to match the new cell's actual curve.
VS III will not power on after the replacement battery sat in storage
Ni-MH cells self-discharge during storage — this battery ships at a partial state of charge, not full. If the cell has dropped below the VS III's BMS recovery threshold (typically around 20V on a 24V Ni-MH pack), the device will not respond to the power button. Connect the VS III to mains power first and allow it to charge for at least two hours before attempting a cold start. Once the pack reaches the BMS recovery floor, the device will boot normally.