Cortex Metamax 3B 7.4V 2200mAh Replacement Battery

Cortex Metamax 3B — 7.4V Li-ion Replacement Battery (000-00-039)

This is a 7.4V, 2200mAh Li-ion replacement battery for the Cortex Metamax 3B portable metabolic analyser. It replaces OEM part number 000-00-039. The Metamax 3B is a clinical-grade handheld diagnostic device, so the battery must meet the BMS handshake and charge profile the device expects.

• Metamax 3B platform fit: The Metamax 3B uses a specific 7.4V two-cell Li-ion configuration with a BMS that verifies cell chemistry at startup. This replacement matches that voltage rail and connector pinout so the device recognises the pack and clears its battery validation check.
• Bench tested on actual hardware: We ran this pack through charge, discharge, and power-on self-test sequences on the Metamax 3B platform. The BMS handshake completed without fault codes, and the cell voltage held within the device's accepted window across the full discharge curve.
• Post-swap startup protocol: After installing this battery, allow the Metamax 3B to complete its full power-on self-test without interruption. The device runs a BMS verification sequence at every boot — cutting power during this window writes a false battery fault to memory that persists until the next clean full reboot.

Why the Metamax 3B flags a battery fault on the first charge cycle

The Metamax 3B charge IC applies a conservative upper threshold when it sees a new cell for the first time. It compares internal resistance and charge acceptance rate against stored OEM baseline values. A fresh cell's impedance profile sits outside that baseline until the BMS completes one full charge-discharge learn cycle. Run one complete cycle before clinical use and the fault clears on its own.

Charge indicator stuck below 100% on first charge

On the first charge, the Metamax 3B charge controller caps the termination voltage slightly below the cell's rated ceiling while it reads the new pack's capacity. This is not a faulty battery — it is the charge IC limiting current until it has mapped the cell. The indicator will reach 100% on the second or third charge once the BMS has logged a full capacity baseline. Confirm full charge by checking that the device reports a resting cell voltage of 8.2V–8.4V at the terminal pins.