About this replacement
Mindray VS800 / WATO EX-20 Series — 11.1V Li-ion Replacement Battery (LI23S001A)
This is an 11.1V, 4400mAh Li-ion battery for the Mindray VS800 patient monitor and compatible WATO EX series devices. It fits the VS800 and VS-800 vital signs monitors used in clinical wards, ICUs, and patient transport. Voltage and capacity match OEM part LI23S001A and alternate reference 022-000382-00.
- VS800 and WATO EX-20 shared platform: These models run the same 11.1V three-cell Li-ion architecture with an identical battery bay connector and BMS handshake protocol. A single battery covers both platforms without modification.
- Bench tested on actual hardware: We cycled this battery through the VS800's startup self-test sequence and confirmed BMS communication, charge acceptance, and runtime flag behaviour. The cell accepted a full charge and cleared the low-battery flag after one complete charge cycle.
- Post-swap startup protocol: After installing this battery, allow the VS800 to complete its full power-on self-test without interruption. The device runs a BMS verification step at boot — cutting power during this window triggers a false battery fault that persists until the next clean reboot.
VS800 low-battery alarm immediately after a confirmed full charge
The VS800 BMS stores OEM chemistry calibration data and compares incoming cell readings against that baseline on first use. A fresh replacement cell has no charge history logged, so the BMS flags it as below threshold until one full charge-discharge cycle completes. This is a calibration state, not a cell fault. Run one full cycle — charge to 100%, allow the device to draw the battery down during normal use, then recharge fully — and the alarm clears.
VS800 will not power on after battery was stored before installation
Li-ion cells self-discharge during storage. If voltage drops below approximately 9V at the pack level, the VS800 BMS enters a protection state and blocks startup entirely. Connect the device to mains power first — do not attempt to boot on battery alone. Leave it on charge for a minimum of 30 minutes before pressing the power button. The charge IC applies a low-current pre-charge phase to recover the cell before resuming normal charge current.