Motorola C1 Replacement Battery 3.7V 1100mAh Li-ion

Motorola C1 / GP378 / GO3988 Series — 3.7V Li-ion Replacement Battery

This 3.7V, 1100mAh Li-ion battery replaces the original pack in the Motorola C1, GO3988, GP378, GP518, and compatible two-way radios. It shares the same voltage rail, form factor, and contact layout as the OEM unit. Capacity figures are taken from the product specification, not third-party sources.

• C1 and GP-series platform fit: These models share a common battery bay depth, contact pitch, and 3.7V single-cell Li-ion architecture. The BMS handshake protocol is consistent across the group, so one pack covers the listed variants without modification.
• Bench tested on actual hardware: We cycled this pack through PTT transmit loads on the C1 platform. The BMS held the voltage rail steady through sustained transmit bursts and tripped correctly at the low-voltage cutoff threshold — no premature lockout observed.
• First-insertion contact cycle: If the charger dock shows a fault LED on first insertion, remove the battery, wipe the gold contact strip with a dry cloth, and reseat firmly. The Motorola platform requires a clean contact cycle to accept the new BMS handshake before charging begins.

Why the C1 cuts out mid-transmission on a freshly inserted pack

A new Li-ion cell ships at storage voltage — typically 3.6V to 3.75V — not at full charge. When PTT is pressed, transmit current draw spikes sharply. If the cell is sitting near the lower end of storage voltage, the BMS can interpret that instantaneous sag as an undervoltage event and trip the output. This is a voltage headroom issue, not a fault with the pack. Charge the battery fully before first use — aim for a complete dock cycle until the charger LED goes green — then retest.

Bar indicator showing one fewer bar than expected after a full charge

The C1 and GP-series radios use a simple voltage-threshold system to drive the bar display — each bar corresponds to a voltage band, not a percentage calculated by a chip. A new cell that has only partial charge may sit in the voltage band that maps to three bars rather than four. This is not a capacity defect. Run a full charge cycle, confirm the dock LED has gone green, then power on — the display should reflect the correct bar count at that resting voltage.