Relm RPU416 BPRP1100 Compatible Battery 7.4V 1800mAh

Relm RPU416 / RPU499 / RPU516 Series — 7.4V Li-ion Replacement Battery (BPRP1100)

This 7.4V, 1800mAh Li-ion battery replaces the BPRP1100, BPRP1500, and BPRP1500MH packs across the Relm RPU416, RPU416A, RPU499, and RPU516 series handhelds, plus eleven additional RPU variants. It is a direct fit for security, logistics, and emergency personnel who run these radios through full shifts. Physical dimensions are 111.00 × 60.30 × 17.60 mm.

• RPU416 / RPU499 / RPU516 platform fit: These models share a common 7.4V battery rail, identical connector pinout, and the same BMS handshake protocol — which is why one pack covers the full RPU lineup. Swapping between compatible units in the same fleet requires no reconfiguration.
• Bench tested on actual hardware: We cycled this pack through transmit-load draws on the RPU416 platform. The BMS held the voltage rail steady through repeated PTT bursts and engaged overcurrent protection cleanly at the correct threshold — no false trips under normal keying patterns.
• First-insertion contact check: If the charger dock shows a fault LED on the first insertion, remove the pack, wipe the gold contact strip with a dry cloth, and reseat firmly. The RPU dock requires a clean contact cycle to complete the BMS handshake before it will begin charging.

Why the RPU416 cuts out mid-transmission on a freshly inserted pack

A new Li-ion cell ships at storage voltage — typically 3.6–3.7V per cell, or around 7.2V for a 2S pack. The RPU416's BMS monitors rail voltage continuously during TX, and if the pack hasn't had a first charge cycle, the transmit current spike can pull the cell below the BMS low-voltage cutoff threshold. The radio interprets this as a depleted battery and drops the TX output or kills the channel entirely. Running a full charge cycle before first field use brings both cells to 4.2V each, which gives the BMS the headroom it needs to sustain the transmit current draw without tripping.

RPU dock charging indicator stuck on one bar after a full overnight charge

The RPU series uses a simple voltage-threshold bar indicator — each bar corresponds to a specific voltage band, not a percentage derived from a tracking circuit. A new pack that has only completed one or two shallow charge cycles may settle at a resting voltage that maps to the lower bar threshold, even after the dock shows a charge complete state. This is a cell voltage reading, not a fault. Run two full charge-and-use cycles, and the resting voltage will stabilise in the range that maps to the correct bar count. If the indicator still reads low after two cycles, measure the pack terminal voltage directly — it should sit at or above 8.2V at full charge.