About this replacement
Fukuda FX-7402 / FCP-7401 Series — 9.6V Ni-MH Replacement Battery (8/HRY-4/3AFD)
This is a 9.6V 3800mAh Ni-MH battery for the Fukuda FX-7402, Cardimax FX-7402, FCP-7311, and FCP-7401 electrocardiograph machines, along with eight additional compatible models. It slots into the battery bay and restores portable ECG operation when AC power is unavailable. Voltage and chemistry match OEM spec exactly — 9.6V Ni-MH, 36.48Wh.
- FX-7402 and FCP series compatibility: These Fukuda ECG models share the same 9.6V Ni-MH battery rail, connector pinout, and BMS handshake protocol. The charge IC in each device is calibrated to this chemistry — swapping to Li-ion is not supported and will trigger a persistent battery fault.
- Bench tested on actual hardware: We cycled this cell through charge, standby, and load draw on the FX-7402 platform. The BMS completed its capacity verification without triggering a fault code, and the charge IC accepted the cell without requiring a manual reset.
- Power-on self-test after installation: After fitting the new battery, allow the device to complete its full startup self-test without interruption. The ECG unit runs a BMS verification sequence at boot — cutting power mid-cycle causes a false battery fault that will persist until the next complete reboot.
Why the FX-7402 alarms low battery with a freshly charged replacement installed
The FX-7402 charge IC applies OEM-calibrated thresholds during its initial BMS verification pass. A new Ni-MH cell has not yet established its internal resistance baseline, so the device reads capacity conservatively and can trigger a low-battery alarm even after a confirmed full charge. This is not a faulty cell — it is the BMS treating an uncharacterised cell with the same caution it applies to a degraded one. Running one complete charge-discharge cycle allows the BMS to map the cell's actual capacity curve and clears the false alarm on subsequent boots.
Device not powering on after the battery sat in storage
Ni-MH cells self-discharge at roughly 1–2% per day at room temperature. A battery that has been in storage for several months can drop below the FX-7402's BMS recovery threshold — typically around 8.5V for a 9.6V pack — at which point the device refuses to power on as a protective measure. Connect the battery to a compatible Ni-MH charger externally before reinstalling, or leave the device on charge via AC for a minimum of two hours to allow the charge IC to recover the cell from its low-voltage state. Once the pack reads above the recovery threshold, normal power-on will resume.