Trimble MCC1821 Replacement Battery 7.4V 3400mAh Li-ion

MOLI MCC1821 / MCR-1821 Series — 7.4V Li-ion Replacement Battery

This is a 7.4V 3400mAh (25.16Wh) lithium-ion battery for Trimble data collectors and GPS positioning devices. It fits the MCC1821, MCR-1821, MCR-1821C, and MCR-1821C/1 series, along with thirteen additional compatible models. This is the battery these instruments use during extended field sessions away from charging infrastructure.

• MCC1821 and MCR-1821 platform compatibility: These models share the same 7.4V power rail, physical form factor, and BMS handshake protocol — one pack covers the full range. Swapping between MCC and MCR variants does not require firmware changes or hardware modification.
• Bench tested on actual hardware: We cycled this pack through a Trimble data collector while logging GPS position data under continuous sensor load. The BMS held voltage within tolerance throughout, and the instrument reported state-of-charge accurately across the full discharge curve.
• Post-install calibration on Trimble instruments: After fitting this pack, run a full calibration cycle through the instrument menu before field deployment. Trimble devices map battery state during that routine, and skipping it causes the low-battery indicator to trigger early — well before actual capacity is exhausted — on the first measurement session.

BMS lockout when the instrument sits unused in a carry case for months

Li-ion cells self-discharge slowly in storage. If the pack drops below approximately 2.5V per cell — around 5.0V total for a 7.4V nominal pack — the BMS enters a protective sleep state and blocks charge input entirely. The charger shows no activity, and the instrument will not power on. To recover the pack, apply a low-current pre-charge using a Li-ion compatible charger that supports recovery mode; this brings the cells back above the BMS wake threshold, typically 3.0V per cell, before normal charging resumes.

Voltage dropout during sustained GPS logging causing readings to reset mid-session

When the instrument runs continuous RTK or static observation, the combined draw from the GNSS module, display, and data logging can sustain a current pull that causes momentary voltage sag. If the pack's cells have aged or were stored in a partially discharged state, this sag dips below the instrument's cutoff threshold and triggers a reset. The instrument restarts, the current logging session ends, and any unsaved data is lost. Charge the pack fully before deployment — confirm the charger LED shows complete before disconnecting — and check that the terminal voltage reads at or above 8.2V before inserting into the instrument.