About this replacement
Fukuda Denshi FX-4010 ECG — 9.6V Ni-MH Replacement Battery (6L2L1)
This 9.6V 3800mAh Ni-MH battery replaces the original pack in the Fukuda Denshi FX-4010 ECG electrocardiograph and compatible models including the FCP-4010 and FCP-4610. It matches OEM part numbers 6L2L1, 8-HRAAFD, 8TH-2400A-2LW, B11644, and LS1506. The cell pack keeps the unit operational for portable cardiac diagnostics when AC power is unavailable.
- FX-4010 / FCP-4010 / FCP-4610 platform fit: These models share the same 9.6V eight-cell Ni-MH architecture, connector pinout, and BMS handshake protocol, which is why a single pack covers the full range. The thermistor line is wired identically across the series, so the charge IC reads cell temperature the same way on all units.
- Bench tested on actual hardware: We ran this pack through a full charge cycle on a compatible FX-series unit and confirmed the BMS accepted the cell stack without fault codes. The charge IC terminated correctly at full capacity and the low-battery threshold did not trip prematurely during the discharge phase.
- Post-swap self-test protocol: After installing this pack, let the FX-4010 complete its full power-on self-test without interruption. Medical-grade BMS verification runs at startup — cutting power mid-sequence writes a battery fault flag that persists until the next clean reboot and can block clinical use unnecessarily.
Why the FX-4010 rejects a new Ni-MH pack during BMS initialisation
The FX-4010 charge IC compares the incoming cell voltage against a stored OEM reference during startup. A new Ni-MH pack that has been in storage often sits between 8.4V and 9.0V — below the threshold the BMS expects for a "known-good" pack. The device then flags the pack as degraded rather than new. Running one complete charge-discharge cycle brings cell voltage and internal resistance into the range the BMS recognises, and the fault clears on the next boot.
Charge indicator stuck below 100% after first installation
This happens because the charge IC applies a conservative current limit on an unrecognised cell stack — it cannot confirm the thermal and impedance profile of the new cells yet. The indicator reflects charge IC confidence, not actual cell state. Run the pack to a natural BMS cutoff discharge, then charge uninterrupted to completion. After that first full cycle, the charge IC recalibrates its endpoint and the indicator reaches 100% correctly.