About this replacement
Motorola SX800 / FV700 Series — 3.6V Ni-MH Replacement Battery (KEBT-086-B)
This is a 3.6V, 700mAh Ni-MH replacement battery for the Motorola SX800, SX800R, SX500R, FV700, and compatible models. It uses OEM part number KEBT-086-B and slots directly into the battery compartment on these compact two-way radios. Swap it in when your original pack stops holding a charge or fails to register in the charger dock.
- SX800 / FV700 platform fit: These models share the same 3.6V Ni-MH cell format, connector pinout, and battery compartment geometry. One pack covers the full SX and FV700 lineup without adapter or modification.
- Bench tested on actual hardware: We cycled this pack through charge and discharge on the SX800 platform. The BMS accepted the handshake correctly, and the radio's bar indicator responded as expected at each voltage threshold across the discharge curve.
- First insertion into the dock: If the dock shows a fault LED on first insertion, remove the pack, wipe the gold contact strip with a dry cloth, and reseat firmly. The Motorola charger dock requires a clean contact cycle to accept the new BMS handshake before charging begins.
Why the SX800 cuts out mid-transmission on a freshly inserted pack
Pressing PTT draws a sharp current spike as the radio switches from standby to transmit. A Ni-MH cell at storage voltage — typically around 1.1–1.2V per cell — has higher internal impedance than a fully charged cell. That impedance causes a momentary voltage drop that the radio's BMS reads as an undervoltage condition, cutting the transmission before it completes. A single full charge cycle before field use brings cell impedance down and eliminates this behaviour.
Bar indicator showing one fewer bar than expected on a new KEBT-086-B
New Ni-MH cells ship at partial state of charge — roughly 40–60% — so the SX800's voltage-threshold bar indicator will read one or two bars low on first insertion. This is not a capacity fault. Run the pack through one complete charge in the dock until the LED goes green, then power on the radio. The bar indicator should reflect a full charge at that point, starting from the 4.2–4.3V fully charged pack voltage.