About this replacement
Biocare PM900S — 14.8V Li-ion Replacement Battery (HYLB-2207)
This 14.8V, 5200mAh lithium-ion battery replaces the OEM pack in the Biocare PM900 and PM900S patient monitors. These portable vital signs monitors use this cell configuration to power continuous ECG, SpO2, and blood pressure acquisition. Capacity figures come from the product data — 76.96Wh.
- PM900 and PM900S platform fit: Both monitor variants share the same battery bay, connector pinout, and BMS communication protocol. A single 4S2P 18650 cell arrangement at 14.8V nominal satisfies the voltage rail both units expect at startup and during peak acquisition loads.
- Bench tested on actual hardware: We cycled this pack through full charge and load discharge on the PM900S platform. The BMS handshake completed without fault flags, and the protection circuit tripped correctly at low-cell threshold — no cell-level imbalance was flagged during the first three cycles.
- Post-install self-test requirement: After installing this battery, allow the monitor to complete its full power-on self-test without interruption. Medical device BMS firmware runs a cell-verification sequence at boot — cutting power mid-sequence registers a persistent battery fault that will not clear until the next clean reboot cycle.
Why the PM900S flags a battery fault on the first boot after a swap
The PM900S BMS stores the previous pack's learned capacity profile in firmware. When a new cell is installed, the monitor's charge IC sees a different internal resistance signature and applies a conservative threshold during the first charge cycle. This can cause the device to flag a battery fault or display an incomplete charge state even when the pack is fully charged. Running one complete charge-to-discharge cycle lets the BMS recalibrate its capacity estimate to the new cell group. Until that learn cycle completes, the displayed state-of-charge percentage will read lower than actual.
Charge indicator stuck below 100% after a full overnight charge
This is a charge IC behaviour, not a defective cell. The PM900S applies a tighter charge termination voltage on an unrecognised pack — typically holding the ceiling at around 16.4V rather than the full 16.8V until the BMS validates the chemistry. Discharge the monitor fully under normal clinical load, then run a complete charge cycle from flat. After that cycle the charge IC releases the conservative limit and the indicator will reach 100%.