Retevis RB628 Replacement Battery BL628 3.7V 1800mAh

Retevis RB628 — 3.7V Li-ion Replacement Battery (BL628 / BL667)

The BL628 / BL667 is a 3.7V, 1800mAh Li-ion battery for the Retevis RB628 handheld two-way radio. It slots directly into the RB628 battery bay and connects to the radio's BMS handshake circuit. Capacity figure is taken from the product specification — 1800mAh at 6.66Wh.

• RB628 platform fit: The RB628 runs a single-cell 3.7V rail with a BMS that monitors cell voltage and transmit-current draw. Both BL628 and BL667 part numbers reference the same physical pack format and connector pinout used across this Retevis compact radio line.
• Bench tested on actual hardware: We cycled this pack through simulated PTT bursts and monitored the BMS response at peak transmit current. The protection circuit held within expected cutoff thresholds and did not trip under normal push-to-talk loads.
• First insertion on the RB628 charger dock: If the dock LED flashes a fault on first seat, remove the pack, wipe the contact strip with a dry cloth, and reseat firmly. The RB628 charger requires a clean contact cycle to complete the BMS handshake before it will begin charging.

Why the RB628 cuts out mid-transmission on a new BL628

A new Li-ion cell ships at storage voltage — typically around 3.6V to 3.7V, not a full charge. When PTT is pressed, transmit current spikes sharply. If the cell voltage is already near the BMS low-voltage threshold, that spike can trigger an overcurrent or undervoltage cutoff, dropping the transmission. This is not a faulty pack — it is the BMS doing its job on a cell that has not yet been fully charged. Charge the battery completely in the dock before the first use in the field.

Bar indicator showing one fewer bar than expected after fitting a new BL628

The RB628 reads battery level through voltage thresholds at the radio's input — it has no fuel gauge chip, only a simple voltage-to-bar map. A new pack at storage voltage reads lower on that map than a freshly charged one, so the radio may show two bars instead of three. This is a voltage reading, not a capacity fault. Fully charge the new pack first and the indicator will reflect the correct full-charge voltage — typically 4.2V at cell level.