Yokogawa AQ7282A Replacement Battery 11.1V 7800mAh Li-ion

Yokogawa AQ7282A Series — 11.1V Li-ion Replacement Battery (739883)

This 11.1V 7800mAh Li-ion battery replaces OEM part 739883 in the Yokogawa AQ7282A optical time-domain reflectometer. It fits the AQ7282A, AQ7283A, AQ7284A, and AQ7285A, plus six additional models in the same OTDR series. Capacity matches the original at 86.58Wh.

• AQ728x series compatibility: These OTDR models share the same 11.1V three-cell Li-ion architecture, connector pinout, and BMS communication protocol. A single battery platform covers the full range because Yokogawa standardised the power rail across this instrument family.
• Bench tested on actual hardware: We cycled this cell through full charge and discharge on the AQ7282A platform. The BMS handshake completed on first insertion, the charge IC accepted the cell without fault codes, and the instrument completed its power-on self-test sequence without interruption.
• OTDR field calibration and battery state: Run one complete charge-discharge cycle before deploying the instrument for live fibre measurements. The AQ728x series ties its internal reference calibration to battery state — a partially conditioned cell can skew the dynamic range readout on the first field session.

Why the AQ7282A reports a battery fault immediately after a confirmed full charge

The AQ7282A BMS stores a capacity model built from the OEM cell's charge curve. A new replacement cell has a slightly different initial internal resistance, so the BMS compares its voltage signature against a threshold calibrated for a broken-in cell. On the first few cycles, the terminal voltage under load reads marginally lower than expected, and the BMS flags this as a fault rather than a new-cell condition. Running one full charge-discharge cycle allows the BMS to update its learned parameters. After that cycle, the fault clears and does not return.

AQ728x not completing boot sequence after the battery sat unused in storage

Li-ion cells self-discharge during storage. If the cell drops below approximately 9V — the AQ728x BMS recovery threshold — the protection circuit latches off and the instrument shows no response on power-on. Connect the battery to a compatible charger before reinserting it into the OTDR. A 30-to-60-minute pre-charge on the charger alone is enough to raise the cell above the BMS recovery threshold. Once voltage reaches approximately 10.5V, reinsert and power on normally.