Yokogawa AQ7275 OTDR Replacement Battery 10.8V 2100mAh Ni-MH

Yokogawa AQ7275 / AQ7270 OTDR — 10.8V Ni-MH Replacement Battery (BDR15D)

This is a 10.8V, 2100mAh Ni-MH replacement battery for the Yokogawa AQ7275 and AQ7270 optical time-domain reflectometers. These are field-portable fiber optic testing instruments used by telecom technicians to locate faults, measure splice loss, and verify cable continuity. The battery matches OEM voltage and capacity to keep the unit running in the field.

• AQ7275 and AQ7270 compatibility: Both OTDR models run the same 10.8V three-cell Ni-MH pack with an identical connector footprint and BMS handshake protocol — swapping between them does not require firmware changes or reconfiguration.
• Bench tested on actual hardware: We cycled this pack through charge and discharge on the AQ7275 platform. The BMS accepted the cell chemistry without flagging a fault, and the charge indicator tracked normally through the full charge curve.
• First-use power-on sequence: After installing this battery, let the OTDR complete its full power-on self-test without interrupting the boot cycle. The instrument runs a BMS verification at startup — cutting power during this sequence triggers a false battery fault that will persist until the next clean reboot.

Why the AQ7275 flags a battery fault after a fresh cell installation

The AQ7275 BMS stores a chemistry baseline from the previous cell and compares the new pack's internal resistance at startup. A fresh Ni-MH cell has higher internal resistance than a broken-in one, and the instrument can read this as an out-of-spec condition. Running one full charge-to-discharge cycle recalibrates the baseline. After that cycle, the fault flag clears and the battery indicator reports accurately.

Charge indicator stuck below 100% on the first charge

The AQ7275 charge IC applies a conservative current limit when it detects a cell with no charge history — this is normal behaviour, not a defective cell. The instrument is measuring the new cell's delta-V curve and applying a reduced termination threshold until it sees a stable charge signature. Disconnect the charger once the indicator stops climbing, then run the OTDR through a normal working session to discharge the pack. On the second charge, the indicator will reach 100% and the charge IC will lock in the correct termination point.