Riegl FG21P Replacement Battery 7.4V 2200mAh Li-ion

Riegl FG21P — 7.4V Li-ion Replacement Battery (70301)

This 7.4V, 2200mAh lithium-ion battery replaces the OEM part 70301 in the Riegl FG21P and FG21-P laser measurement instruments. These are professional surveying and scanning tools used in field mapping and range-finding applications. Voltage and capacity match the original specification exactly.

• FG21P and FG21-P compatibility: Both model variants share the same 7.4V battery platform, connector pinout, and BMS handshake protocol. One replacement covers either unit without modification.
• Bench tested on actual hardware: We cycled this cell pack through charge and discharge on the FG21P platform. The BMS communicated correctly, accepted charge without fault flags, and held voltage within the instrument's operating threshold across the full discharge curve.
• Field warm-up on a fresh battery: After fitting a new or fully charged battery, allow approximately two minutes before taking measurements. The FG21P's self-levelling motor and laser emitter both draw current during warm-up, and the instrument's internal temperature stabilisation affects measurement accuracy until the unit reaches operating state.

Laser distance readings drifting as battery drains on the FG21P

The FG21P drives its laser emitter and rangefinding processor from the same 7.4V cell. As voltage drops toward the lower end of the discharge curve, laser output power decreases and the time-of-flight processor receives weaker return signals. This causes measured distances to drift slightly before the low-battery warning triggers. If readings start showing inconsistency at range, check cell voltage — anything below 6.8V under load is the threshold where accuracy degrades on this instrument.

Auto-levelling stops mid-cycle after a battery swap

The FG21P's self-levelling motor pulls a brief current spike at startup — higher than the steady-state draw of the laser or display. If the replacement battery has a conservative BMS trip threshold, this inrush can trigger an overcurrent cutoff before levelling completes. The fix is a full charge cycle before first use, bringing the cell to 8.4V so it can deliver that startup current without the BMS intervening. If the unit still stops mid-level after a full charge, check that the battery contacts are clean and seating flush — a high-resistance connection amplifies the voltage sag at the BMS sense line.