About this replacement
Yokogawa AQ7260 Series — 11.1V Li-ion Replacement Battery (3UR18650F-2)
This 11.1V Li-ion battery replaces part number 3UR18650F-2 in the Yokogawa AQ7260 OTDR. It fits the AQ7260, AQ7261, AQ7264, and AQ7265 platforms. Capacity is 5200mAh (57.72Wh), matched to the original specification.
- AQ7260 series compatibility: The AQ7261, AQ7264, and AQ7265 share the same battery bay geometry, connector pinout, and BMS handshake protocol as the AQ7260. All four models run the same 11.1V three-cell Li-ion configuration, so one pack covers the full platform.
- Bench tested on actual hardware: We ran this pack through instrument power-on, laser module initialisation, and a sustained OTDR measurement sequence. The BMS held the voltage rail steady through the laser pulse burst cycle and did not trip on the short-duration current spikes at acquisition start.
- Pre-deployment calibration: After installing this pack, run a full calibration cycle through the AQ7260 instrument menu before heading to site. The instrument maps battery state during that sequence. Skip it, and the low-battery warning will trigger early on the first measurement session — even with a fully charged pack.
AQ7260 BMS lockout after the pack sat unused in a carry case for months
Li-ion cells self-discharge over time. If the AQ7260 sat in a carry case for several months with the battery installed, cell voltage can drop below the BMS protection threshold — typically around 2.5V per cell. At that point the BMS opens the output circuit entirely, and the instrument shows no sign of life even when connected to the charger. The fix is to connect the charger and leave it for at least two to four hours without attempting to power on the instrument — most BMS circuits include a trickle-recovery path that slowly brings cell voltage back up to the reactivation threshold near 3.0V per cell. Once the BMS resets and the charge LED responds normally, proceed with a full charge cycle before use.
AQ7260 shuts down mid-measurement with no low-battery warning
This happens when the combined draw of the laser driver, DSP, and display pulls the pack voltage below the BMS cutoff threshold during a long acquisition — particularly on high-dynamic-range test settings that increase laser pulse repetition. It is not a capacity failure; it is a sustained-load voltage sag on a partially discharged pack. Start each field session above 11.4V — check the battery indicator in the instrument status screen before beginning a test run. If the instrument cuts out mid-acquisition, reconnect to AC where possible and allow a full recharge before continuing.