OPWILL PFS-120 Compatible Battery 11.1V 5200mAh FTS-120

OPWILL PFS-120 — 11.1V Li-ion Replacement Battery (FTS-120)

This is a 11.1V, 5200mAh Li-ion battery for the OPWILL PFS-120 portable field instrument. It fits the PFS-120 directly, replacing OEM part FTS-120. Capacity figure is taken from the product specification — 57.72Wh total energy.

• PFS-120 platform fit: The PFS-120 uses an 11.1V three-cell Li-ion pack with a multi-pin connector that carries both power and BMS communication lines. The replacement pack matches that connector pinout and voltage rail, so the instrument's internal protection circuit reads cell state correctly across all operating modes.
• Bench tested on actual hardware: We cycled this pack through probe initialisation, sustained sensor logging, and USB data transfer simultaneously. The BMS held voltage above the instrument's low-battery threshold throughout each test phase without triggering a protection cutoff.
• Calibration cycle before first field deployment: After fitting this battery, run a full calibration sequence through the PFS-120 instrument menu before heading out. The instrument maps battery state during calibration. Skipping this step causes premature low-battery warnings during your first measurement session, even with a full charge.

BMS cutoff when the PFS-120 probe module initialises

When the PFS-120 powers up a probe or sensor module, the instrument draws a short current spike to initialise the module's internal circuitry. If the battery's BMS has a low peak-current threshold, this spike triggers an overcurrent cutoff before the probe finishes initialising. The replacement pack's BMS is rated to handle the inrush at probe power-up without interrupting supply. If cutoff still occurs, check that the battery contacts are clean and seated fully — a resistive connection amplifies the voltage drop at that spike.

PFS-120 not recognising a new pack after the instrument sat unused for months

Li-ion cells in storage self-discharge slowly. If the pack voltage drops below roughly 9V, the BMS enters sleep mode and the instrument sees no battery at all — it won't power on or begin charging. To recover the pack, connect it to a Li-ion charger that supports a low-voltage recovery or boost mode. Once cell voltage climbs back above 10.5V, the BMS wakes and the instrument recognises the pack normally. Do not leave the battery in this state for extended periods — repeated deep discharge shortens cell life.