Dopod 35H00078-02M C800 Replacement Battery 3.7V 2400mAh

Dopod C800 / C858 — 3.7V Li-Polymer Replacement Battery (35H00078-02M)

This is a 3.7V, 2400mAh lithium-polymer cell for the Dopod C800 and C858 Windows Mobile smartphones. It replaces OEM part numbers 35H00078-02M and HERA160. If your original cell no longer holds a charge or shuts down unexpectedly, this cell restores full electrical capacity to the device.

• C800 and C858 compatibility: Both models share the same battery bay dimensions, connector pinout, and BMS communication protocol. One cell covers both variants without modification.
• Bench tested on actual hardware: We ran this cell through full charge and discharge cycles on a C800 unit. The BMS accepted the cell without triggering a fault, charge IC engaged correctly, and the fuel gauge IC tracked state-of-charge without error flags.
• Fuel gauge recalibration on first use: After installing this cell, disable any power-saving fast charge mode and complete one full discharge-charge cycle before normal use. The fuel gauge IC on these Windows Mobile devices calibrates its coulomb counter against the actual discharge curve — skipping this step causes the percentage readout to drift off early.

Sudden shutdown at 20–30% on the Dopod C800

This is a voltage cliff issue, not a capacity problem. When the modem radio or display draws peak current, an aged or uncalibrated cell cannot sustain the voltage rail above the BMS cutoff threshold — even if the fuel gauge still shows charge remaining. The BMS trips and the phone cuts out. Completing one full discharge cycle to 3.0V and recharging to 4.2V forces the fuel gauge IC to remap its curve to the new cell, which eliminates most false-floor shutdowns.

Battery percentage jumping erratically after cell swap

The fuel gauge IC on the C800 stores a discharge model calibrated to the original cell's impedance and capacity. A new cell has a different internal resistance profile, so the IC's coulomb counter reads incorrectly until it is reset. You will see the percentage jump 10–15 points in either direction, especially under screen or radio load. Discharge the phone fully until it powers off, then charge uninterrupted to 100% — this forces the fuel gauge IC to rewrite its reference curve against the new cell.