JDSU GC724A Replacement Battery 11.1V 5200mAh Li-ion

JDSU GC724A / JD723A — 11.1V Li-ion Replacement Battery

This is an 11.1V, 5200mAh (57.72Wh) Li-ion battery for the JDSU GC724A optical power meter and JD723A light source. Both units are handheld fiber optic test instruments used in telecoms field work. This pack restores full operating voltage to either device without modification.

• GC724A and JD723A compatibility: Both instruments share the same 11.1V three-cell Li-ion architecture and use the same battery bay dimensions and connector pinout. The BMS handshake protocol is identical across the two platforms, so one pack covers both without any firmware conflict.
• Bench tested on actual hardware: We cycled this pack through the GC724A's power-up sequence, including optical module initialisation. The BMS held steady through the brief current spike at probe activation and maintained stable output across a sustained measurement load without tripping the protection circuit.
• Pre-deployment calibration cycle: After fitting this pack, run a full calibration sequence through the instrument's menu before heading into the field. The GC724A maps battery state during calibration — skipping this step causes the low-battery indicator to fire early during the first measurement session, even with a fully charged pack.

BMS lockout after the GC724A sat unused in a carry case for months

Li-ion cells self-discharge slowly during storage. If a pack sits long enough, cell voltage drops below the BMS's minimum recovery threshold — typically around 2.5V per cell, or roughly 7.5V across the full 11.1V pack. At that point the BMS enters a locked state and refuses a standard charge cycle. To recover, connect the pack to the charger and leave it for at least 30 minutes before the instrument registers any charge activity — many chargers apply a low-rate pre-charge trickle below 3.0V per cell to bring the cells back into normal range. If the charger shows no response after 45 minutes, the cells may be below recoverable threshold.

GC724A powers on but shuts off during USB data transfer to PC

USB data transfer adds a second load on top of the instrument's active measurement circuitry. On a degraded or partially discharged pack, that combined draw pulls voltage low enough to trigger the BMS undervoltage cutoff — the instrument shuts down even though the display was showing adequate charge. This is not a fault with the port or the software. Charge the pack to full before initiating any USB transfer session, and confirm the charger LED shows a complete cycle rather than going by the on-screen percentage, which recalibrates to new cells over the first few charge cycles.