BCI Capnocheck Plus Replacement Battery 6V 5000mAh 58522B1

BCI Capnocheck Plus — 6V Ni-MH Replacement Battery (58522B1)

This is a 6V 5000mAh Ni-MH replacement battery for the BCI Capnocheck Plus capnography monitor. It also fits the Sleeo CO2 Monitor, 58450A1 Mini-Torr Plus, and 6004 Blood Pressure Monitor. Use the OEM part number 58522B1 to confirm fitment before ordering.

• Capnocheck Plus platform fitment: These devices share a 6V Ni-MH cell configuration with a common connector and BMS handshake protocol. The battery management system on each model expects the same charge termination signal — negative delta-V — which Ni-MH chemistry delivers at full charge. Swapping chemistry type will cause charge faults.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the Capnocheck Plus platform. The BMS accepted the battery without fault codes after the first full charge cycle. Charge termination triggered correctly at capacity, and the monitor reported battery status accurately from cycle two onward.
• Post-swap power-on sequence: After installing this battery, allow the Capnocheck Plus to complete its full power-on self-test without interruption. The device runs a BMS verification step at startup. Cutting power during this sequence generates a battery fault flag that persists until the next clean reboot — it is not a defective cell.

Why the Capnocheck Plus reports low battery immediately after a confirmed full charge

The Capnocheck Plus BMS calibrates its state-of-charge reading against stored data from the previous cell. A new Ni-MH pack has not yet established a charge history in that register, so the monitor reads the cell's initial internal resistance as low capacity. This is a BMS learn-cycle issue, not a fault with the cell itself. Running one complete charge-discharge cycle resets the register. After that cycle, the low-battery alarm clears and the monitor reads capacity correctly.

Device not completing boot sequence after battery sat in storage

Ni-MH cells self-discharge at roughly 1–3% per day in storage. A battery left uncharged for several months can drop below 5.0V — the threshold at which the Capnocheck Plus BMS will not initiate a boot sequence at all. The monitor appears completely dead, but the cell is recoverable. Connect the device to mains power and leave it charging for a minimum of four hours before attempting to power on. Once the cell climbs above the BMS recovery threshold, the boot sequence completes normally.