BCI MCR-1821J/1-H Capnocheck II Compatible Battery 7.4V 2600mAh

BCI Capnocheck II Capnograph Pulse Oximeter — 7.4V Li-ion Replacement Battery (MCR-1821J/1-H)

This is a 7.4V, 2600mAh Li-ion replacement battery for the BCI Capnocheck II Capnograph Pulse Oximeter. It fits handheld units used for simultaneous end-tidal CO2 and SpO2 monitoring during portable clinical assessments. Confirmed compatible with Capnocheck II, Capnocheck ll, Capnocheck 8400, and Capnocheck 8401 models using OEM part references MCR-1821J/1-H, OM0032, and 6082.

• Capnocheck 8400 and 8401 platform fit: These models share the same 7.4V battery rail, physical connector, and BMS handshake protocol as the Capnocheck II. One replacement cell covers the full platform without modifications or adapters.
• Bench tested on actual hardware: We ran this cell through the Capnocheck boot sequence and monitored BMS communication during startup. The battery reported state-of-charge correctly and passed the device's internal power verification without throwing a fault flag.
• Post-swap startup protocol: After installing this battery, allow the device to complete its full power-on self-test cycle without interruption. The Capnocheck BMS runs a chemistry verification step at startup — cutting power mid-sequence stores a false battery fault that persists until the next complete reboot.

Why the Capnocheck II won't complete its boot sequence on a new battery

The Capnocheck II runs a BMS learn cycle during its first few charge-discharge passes on a new cell. Until that cycle completes, the device's charge controller applies a conservative capacity estimate that can fall below the boot threshold. This causes the unit to stall mid-startup or reset before reaching the monitoring screen. One full charge followed by a full discharge resolves the issue — after that, the BMS registers the actual cell capacity and boot proceeds normally.

Charge indicator stuck below 100% on first charge after battery swap

On first charge, the Capnocheck's charge IC applies a reduced current ceiling to an uncharacterised new cell — this is intentional, not a fault. The indicator plateaus early because the IC has not yet confirmed the cell's internal resistance profile. Run one complete charge cycle to completion without interrupting the charge, then discharge the device fully during normal use. On the second charge, the IC updates its model and the indicator reaches 100% at the correct point.