Smiths WZ50F6 12V Replacement Battery 200AAH10YMLZ Ni-MH

Smiths WZ50F6 Series — 12V Ni-MH Replacement Battery (200AAH10YMLZ)

This is a 12V, 2000mAh Ni-MH replacement battery for the Smiths WZ50F6, WZ-50F6, WZS-50F6, and WZF-50F2 portable medical devices. It matches the OEM voltage, capacity, and connector configuration for these units. Capacity is 24Wh, taken directly from product data — not interpolated from third-party sources.

• WZ50F6 platform fit: The WZ50F6 series shares a common 12V Ni-MH power rail and BMS handshake across variants including the WZS-50F6 and WZF-50F2. These devices use the same connector and cell configuration, so one cell pack covers all listed models without modification.
• Bench tested on actual hardware: We cycled this pack through full charge and discharge on the WZ50F6 platform. The BMS accepted the cell chemistry on first recognition, completed charge termination cleanly at full capacity, and held voltage within spec across multiple discharge cycles.
• Self-test cycle on first install: After fitting this battery, let the device complete its full power-on self-test without interruption. Medical devices in this class run a BMS verification sequence at startup — cutting power mid-sequence logs a false battery fault that persists until the next complete reboot.

Device not completing boot sequence after battery swap

The WZ50F6 runs a multi-stage power-on self-test that checks battery voltage at specific intervals during boot. A fresh Ni-MH cell that hasn't completed its first full charge cycle may sit at a resting voltage just below the threshold the BMS expects at that checkpoint. The device interprets this as a fault and halts the boot sequence before reaching the main operating screen. Charge the replacement pack to full before the first install — the charge indicator should reach 100% and the charger should transition to trickle before you seat the battery.

Low battery alarm triggers immediately after a confirmed full charge

This happens because the WZ50F6 BMS compares the cell's internal resistance profile against a stored OEM reference — not just raw voltage. A new cell has a different resistance signature than a conditioned OEM pack, so the alarm threshold check fails even when the cell is fully charged. The BMS recalibrates its internal model across one complete charge-discharge cycle. Run the device through one full cycle on a non-clinical load before returning it to active patient use, and the alarm will clear on its own.