About this replacement
Sonim XP10 / XP9900 — 3.85V Li-Polymer Replacement Battery (BAT-05000-01S)
This is a 3.85V, 4850mAh (18.67Wh) Li-Polymer cell for the Sonim XP10 and XP9900 rugged smartphones. It replaces OEM part BAT-05000-01S and fits the same battery bay without modification. Use it when the original cell no longer holds charge through a full field shift.
- XP10 and XP9900 compatibility: Both handsets share the same battery bay dimensions, connector pinout, and BMS handshake protocol. The 84.80 × 59.90 × 6.00mm cell format matches the original cavity, and the BMS communicates over the same fuel gauge line used by the XP10's Qualcomm power management IC.
- Bench tested on actual hardware: We ran this cell through charge and discharge cycles on the XP10 platform. The BMS accepted the USB-PD charge handshake on the second cycle, and the coulomb counter tracked cell state correctly after one full calibration cycle.
- Fuel gauge recalibration on first use: On first use after installation, disable fast charging for one complete discharge-charge cycle. This lets the fuel gauge IC map its calibration curve against the new cell before high-current charging pushes current into an uncalibrated state. Skip this step and the percentage readout will drift for several days.
Sudden shutdown at 20–30% on the Sonim XP10 after a cell swap
The XP10 pulls hard on the battery whenever the LTE modem transmits at full power or the screen brightness peaks. A new cell with an uncalibrated fuel gauge IC can report 25% remaining while the actual resting voltage is already near 3.5V. Under modem load, voltage dips below the BMS cutoff threshold and the phone shuts off. One full discharge-to-3.6V, then a full charge cycle, gives the coulomb counter enough data to anchor its curve correctly.
XP10 not powering on after the replacement battery sat in storage
Li-Polymer cells shipped or stored for several weeks can drop below 3.0V per cell. The XP10's BMS enters lockout at that voltage to prevent damage, and the phone will show no response — no boot screen, no charging indicator. Connect the device to a wall adapter rated at 5V/2A and leave it for 20–30 minutes without pressing the power button. The BMS uses a trickle pre-charge stage to bring the cell above 3.0V before allowing normal charge current to flow.