Mentor 22-4501 Replacement Battery 4.8V 2300mAh Ni-MH

Mentor 22-4501 / 22-4505 / 22-4515 Ophthalmoscope — 4.8V Ni-MH Replacement Battery (110399)

This is a 4.8V, 2300mAh Ni-MH replacement battery for the Mentor 22-4501, 22-4505, and 22-4515 Ophthalmoscope series. It replaces OEM part number 110399 and fits the original battery compartment without modification. Cell chemistry matches the OEM specification — Ni-MH — which the device's charge circuit expects.

• 22-4501 / 22-4505 / 22-4515 platform fit: All three Mentor Ophthalmoscope models share the same 4.8V battery rail, connector pinout, and BMS handshake requirements. One part number covers all three variants because the charge management circuit is identical across the platform.
• Bench tested on actual hardware: We cycled this cell through charge and full-load discharge on the bench. The BMS accepted the cell without fault codes, completed charge termination via delta-V detection, and held voltage above the low-battery threshold across the full discharge curve.
• Power-on self-test — do not interrupt: After installing this battery, let the device run its full power-on self-test cycle without switching it off. The Mentor Ophthalmoscope runs BMS verification at startup — cutting power mid-sequence stores a false battery fault that persists until the next complete reboot.

Why the Mentor Ophthalmoscope flags a battery fault on a freshly charged new cell

The device's BMS uses a learned delta-V profile to verify battery health at startup. A new cell fresh out of packaging has not completed a conditioning cycle, so its voltage rise curve during the self-test does not yet match the stored OEM reference. The BMS interprets this mismatch as a degraded or incompatible cell and raises a fault flag. Running one full charge-to-discharge cycle before clinical use allows the BMS to re-baseline against the new cell's actual delta-V signature and clear the fault.

Charge indicator stalling below 100% on first charge

On the first charge, the Mentor charge IC applies a conservative current limit because the new cell's internal resistance reads higher than a broken-in cell. This causes the charge cycle to run longer than expected and the indicator to stall — often between 80% and 95% — before the termination threshold triggers. The cell is not faulty; it is still accepting charge. Leave the device on the charger until the indicator advances to full, then run one complete discharge before the next charge cycle to normalise the resistance reading.