About this replacement
EXFO FOT-5200 Series — 3.7V Li-Polymer Replacement Battery (880X264)
This 3.7V 1800mAh Li-Polymer battery replaces the OEM pack in the EXFO FOT-5200 and FOT-5200 CWDM Channel Power Analyzer. Both instruments are handheld optical time-domain reflectometers used for fiber optic network testing and diagnostics in the field. Capacity is 1800mAh (6.66Wh), matching OEM part numbers 880X264, GP-2150, and GP103045L180R.
- FOT-5200 and FOT-5200 CWDM shared platform: Both units run on the same 3.7V power rail with an identical physical connector and BMS handshake protocol. One battery pack covers both variants without modification.
- Bench tested on actual hardware: We cycled this pack through the FOT-5200 charge and discharge sequence and confirmed the BMS negotiated correctly at startup. The protection circuit held within spec across OTDR pulse launches, which draw brief current spikes as the laser fires.
- Post-install calibration before field deployment: After fitting this pack, run a full calibration cycle through the FOT-5200 instrument menu before heading out. The instrument maps battery state during calibration — skip it and the low-battery warning triggers early on your first measurement session, cutting a job short.
BMS lockout after the FOT-5200 sat unused in a carry case for months
Li-Polymer cells self-discharge slowly during storage. If the pack drops below roughly 2.5V per cell, the BMS trips into deep-discharge lockout and the instrument shows no response — not even a charging indicator. The charger sees an apparent open circuit and stops attempting to charge. To recover, connect the FOT-5200 to its OEM charger and leave it undisturbed for at least 90 minutes before pressing power — some BMS circuits require a slow trickle before they re-initialise the charge path at the standard 4.2V ceiling.
FOT-5200 shutting down mid-measurement with no low-battery warning
This failure mode is not a capacity problem — it is a voltage sag problem. During an OTDR pulse launch, the laser module draws a sharp current spike that momentarily pulls cell voltage below the BMS under-voltage threshold, triggering a protective shutdown before the fuel gauge registers low. A cell that reads 40% on the display can still cause this if internal resistance has climbed with age. Fit the new pack, run the calibration cycle, and confirm pulse-launch shutdowns stop occurring before returning the instrument to service.