Cefar MYO REH AB4 Replacement Battery 7.2V 2000mAh

Cefar MYO REH AB4 / Myo 4 Max / Rehab 4 — 7.2V Ni-MH Replacement Battery (120466)

This is a 7.2V 2000mAh Ni-MH replacement battery for the Cefar MYO REH AB4, Myo 4 Max, and Rehab 4 portable electrotherapy units. It matches OEM part numbers 120466 and BATT/110466. These handheld muscle stimulators draw consistent current through each therapy session, and the original Ni-MH cells degrade faster than most users expect.

• MYO REH AB4, Myo 4 Max, and Rehab 4 compatibility: These three units share the same 7.2V Ni-MH battery format, connector type, and BMS handshake protocol. One replacement cell covers all three platforms without adapter modifications.
• Bench tested on actual hardware: We cycled this cell through the Cefar charge-discharge profile and confirmed the BMS accepted the new pack without triggering a false fault. Capacity measured within 3% of the 2000mAh rating by cycle three.
• Power-on self-test protocol: After installing this battery, let the device run its full startup self-test without removing power or pressing additional buttons. The Cefar BMS runs a chemistry verification at boot — interrupting it locks in a battery fault flag that clears only on the next clean reboot cycle.

Why the Cefar MYO REH AB4 alarms low battery with a freshly charged replacement

The Cefar BMS sets its low-battery threshold against the charge profile of a conditioned OEM cell. A new replacement cell has a slightly flatter voltage curve in the first two cycles, which sits below that threshold at peak load. The device reads this as low battery even though the pack is fully charged. Run one complete charge-discharge cycle before clinical use — by cycle two, the cell's voltage curve stabilises and the alarm stops triggering.

Cefar unit won't power on after the battery sat in storage

Ni-MH cells self-discharge at roughly 20–30% per month in storage. If the replacement battery sat uninstalled for several months, its resting voltage may have dropped below the BMS recovery threshold — typically around 5.5V for a 7.2V pack. A standard charger won't engage because the BMS sees an undervoltage condition and blocks the charge circuit. Connect the unit to the Cefar charger and hold the power button for five seconds — this forces a trickle-charge recovery mode that brings the cell back above the 6.0V re-initialisation threshold.