About this replacement
Motorola Droid X MB810 — 3.7V Li-ion Replacement Battery (BH5X / SNN5865A)
This is a 3.7V, 1200mAh Li-ion cell built to replace the original BH5X battery in the Motorola Droid X (MB810) and Droid X2 (ME811) smartphones. It slots into the same battery bay and connects to the same charge IC used by the factory cell. Dimensions are 65.05 × 41.97 × 4.78mm — a direct size match for the MB810 chassis.
- MB810 and ME811 compatibility: Both the Droid X and Droid X2 share the BH5X footprint and the same 3.7V charging rail. The connector pinout and BMS handshake are identical across those variants, so one cell covers the full range.
- Bench tested on actual hardware: We cycled this cell through the MB810's charge IC and confirmed the BMS accepted the full charge profile without dropping into fault mode. Voltage under screen-on load held within the expected discharge curve.
- Fuel gauge recalibration on first install: On first use after fitting, run one complete discharge down to auto-shutoff, then charge uninterrupted to 100%. This gives the Droid X's coulomb counter a clean reference curve against the new cell before you rely on percentage readings.
Sudden shutdown at 20–30% on the Droid X after a cell swap
The MB810's fuel gauge IC maps its low-voltage cutoff threshold against the discharge curve of the original cell. A new cell with a slightly different internal resistance profile can hit the voltage floor under modem or display load while the gauge still reads 20–30%. The phone interprets the voltage sag as a hard fault and cuts power before the percentage drops further. One full calibration cycle — discharge to shutoff, then a full uninterrupted charge — resets the coulomb counter and tightens up the shutdown point.
Phone reports wrong battery percentage after fitting the BH5X replacement
The Droid X stores the previous cell's discharge curve in its fuel gauge IC. When a new cell goes in, the stored curve no longer matches the actual voltage-to-capacity relationship of the replacement. The gauge reads an interpolated percentage against stale data, so numbers jump or sit high until a full cycle runs. Discharge the phone to auto-shutoff, then charge to 100% without interruption — after that cycle the IC recalibrates and percentage tracking stabilises.