Sepura STP8000 7.4V Replacement Battery 300-00635

Sepura STP8000 Series — 7.4V Li-ion Replacement Battery (300-00635)

This 7.4V, 3300mAh lithium-ion battery replaces the original pack in the Sepura STP8000, STS8000, STP8038, STP8030, and over 26 compatible variants. It is a direct cell replacement for professional land mobile radios used by emergency services and security teams. OEM part numbers covered include 300-00635, 300-00631, 300-01175, 300-01852, 300-01853, 300-00634, and 300-01174.

• STP8000 and STS8000 platform compatibility: These models share a common battery bay geometry, connector pinout, and BMS handshake protocol across the STP8030 and STP8038 variants — one cell format fits the full series without modification.
• Bench tested on actual hardware: We ran this pack through charge acceptance and transmit-load cycles on the STP8000 platform. The BMS handled repeated PTT current spikes without tripping, and the charger dock accepted the pack through a full charge cycle to green.
• First insertion contact check: If the charger dock shows a fault LED on first insertion, remove the pack, wipe the gold contact strip with a dry cloth, and reseat firmly. The STP8000 dock requires a clean contact cycle to complete the BMS handshake before charging begins.

Why the STP8000 cuts out mid-transmission on a freshly inserted battery

The STP8000 draws a sharp current spike the moment PTT is pressed — transmit current can hit several amps in under 100 milliseconds. A new pack shipped at storage voltage (typically 3.7–3.8V per cell) has a higher internal impedance than a fully charged cell. That impedance causes a voltage sag under transmit load that can trip the BMS overcurrent threshold before the radio completes the transmission. Charge the pack fully to 8.4V before the first operational shift to bring cell impedance down to normal working range.

Bar indicator showing one fewer bar than expected after fitting this pack

The STP8000 uses a voltage-threshold bar indicator — each bar maps to a fixed voltage window, not a fuel gauge chip. A pack shipped at storage voltage will sit below the top threshold and display one or two bars even though the cells are not depleted. This is storage voltage, not a faulty cell. Put the pack on charge until the dock shows green, then reinsert — the indicator will read correctly at full charge voltage of 8.4V.