Sokkia Archer 2 Data Collector Replacement Battery 3.7V 13600mAh

Sokkia Archer 2 / FC-500 Data Collector — 3.7V Li-ion Replacement Battery (1003778-01)

This 3.7V, 13600mAh (50.32Wh) lithium-ion battery replaces OEM part 1003778-01 in the Sokkia Archer 2 and FC-500 handheld data collectors. Both units are field-grade survey instruments used for GPS capture and measurement logging on construction and land survey sites. The cell format, connector, and BMS handshake match the original pack.

• Archer 2 and FC-500 compatibility: Both devices share the same battery bay dimensions, 3.7V power rail, and OEM connector pinout. The BMS in each unit reads the same charge-state protocol, so no firmware workaround is needed when swapping between these models.
• Bench tested on actual hardware: We ran this pack through charge, discharge, and GPS-active logging cycles on the Archer 2. The BMS held stable voltage under sustained sensor load and did not trip during data transfer to an external device.
• First-use calibration on the Archer 2: After installing, run a full calibration cycle through the instrument menu before field deployment. The Archer 2 maps battery state during calibration — skipping this step causes premature low-battery warnings during your first measurement session.

BMS cutoff when the Archer 2 initialises GPS or a connected sensor module

At power-up, the Archer 2 draws a brief current spike as it initialises the GPS receiver and any connected sensor modules. If the battery BMS registers this spike above its threshold — common with a partially discharged or freshly installed pack — it cuts output to protect the cells. This is not a fault in the instrument. Charge the replacement pack to 100% before first use and allow the BMS to complete its initial handshake with the device. A full charge brings cell voltage to approximately 4.2V per cell, giving the BMS enough headroom to pass the initialisation surge without tripping.

Archer 2 shows erratic charge percentage immediately after a new pack is installed

The Archer 2 uses a voltage-threshold indicator that references stored cell data from the previous pack. When a new battery is installed, the device has no baseline for the new cells and displays an inaccurate percentage — often jumping between readings on reboot. This resolves after one full charge-to-discharge-to-charge cycle, which forces the instrument to recalibrate its thresholds against the new cell voltage curve. Run that cycle through the instrument menu rather than just charging passively via USB. After the cycle completes, the indicator should track correctly from 4.2V down through the discharge range.