Cobra LI3900 Replacement Battery 7.4V 700mAh Li-ion

Cobra LI3900 / LI4900 Series — 7.4V Li-ion Replacement Battery (MN-0160001)

This 7.4V 700mAh Li-ion cell replaces the factory pack in Cobra LI3900, LI3950, LI4900, and LI5600 two-way radios. It matches the OEM voltage rail and connector footprint so the charger dock reads the pack correctly. Capacity is drawn from product data: 700mAh / 5.18Wh.

• LI3900 / LI4900 series compatibility: These models share a common 7.4V two-cell architecture and the same BMS handshake protocol. One replacement pack covers the full range because the dock reads voltage and pack ID from the same contact strip across all listed models.
• Bench tested on actual hardware: We cycled this pack through PTT-heavy transmit loads on the LI3900 platform. The BMS handled the transmit current spike without tripping overcurrent cutoff, and the dock accepted the charge cycle on first insertion.
• Contact strip maintenance on the LI-series dock: If the dock shows a fault LED after swapping this pack in, remove the battery and wipe the gold contact strip with a dry cloth before reseating. The Cobra LI-series dock requires a clean contact cycle to complete the BMS handshake — a fingerprint or residue on the strip is enough to block it.

Why the LI3900 cuts out mid-transmission on a fresh pack

The LI3900's transmit draw spikes sharply the moment PTT is pressed. If the replacement pack's BMS has a conservative overcurrent threshold — common in cells shipped at storage voltage — that spike can trigger a momentary BMS cutoff before the radio finishes keying up. The fix is to run two or three full charge cycles before heavy PTT use. After conditioning, the BMS learns the transmit load profile and stops tripping on the initial surge.

Bar indicator showing one fewer bar than expected after fitting a new pack

New Li-ion cells leave the warehouse at roughly 3.7V per cell — storage voltage, not full charge voltage. The LI-series radio maps voltage directly to bar count, so a pack at storage voltage reads as partially depleted even though the cell is new and healthy. Charge the pack fully before judging bar count. A full charge brings each cell to approximately 4.2V, and the bar indicator should reach its top reading at that point.