Plum E800 Replacement Battery 3.7V 1100mAh PM-BATE800

Plum E800 — 3.7V Li-ion Replacement Battery (PM-BATE800)

This is a 3.7V, 1100mAh Li-ion replacement battery for the Plum E800 smartphone. It replaces OEM part PM-BATE800 and fits the E800 directly. Capacity is rated at 4.07Wh — matching the original cell specification.

• E800 fitment: The E800 uses a single-cell 3.7V nominal Li-ion configuration with a low-current BMS. This replacement cell matches the connector pinout and voltage rails that the phone's charge IC expects, so the handshake between the battery and the board completes without errors.
• Bench tested on actual hardware: We cycled this cell through full charge and discharge on an E800 board. The BMS accepted the charge IC handshake on the first connection, and protection circuits — overcurrent, overvoltage, and thermal — all triggered at expected thresholds.
• Fuel gauge recalibration on first cycle: After installing this cell, disable fast charging if available and run one complete discharge down to automatic shutoff, then charge uninterrupted to 100%. The E800's fuel gauge IC calibrates its coulomb counter against the new cell's discharge curve during that first cycle — skipping it causes erratic percentage readings in the first few days of use.

Why the E800 reports wrong battery percentage after a cell swap

The E800's fuel gauge IC builds its charge estimate from a stored discharge curve tied to the old cell. When a new cell goes in, that curve no longer matches actual cell behaviour — so the reported percentage drifts from the real state of charge. This shows up as sudden jumps in the percentage indicator or a reading that stays stuck at one value for long stretches. One full uninterrupted discharge-to-shutoff and charge-to-100% cycle forces the coulomb counter to relearn the new cell's curve and corrects the readout.

Sudden shutdown at 20–30% on the replacement cell

This happens when the cell voltage drops below the modem or screen load threshold before the fuel gauge reaches 0%. Under GSM transmission bursts or screen-on current draw, a cell with any internal resistance will sag in voltage faster than the gauge predicts. The E800 interprets this voltage cliff as a hard cutoff and shuts down even though the displayed percentage still reads in the 20–30% range. Completing a full recalibration cycle — discharge to shutoff, uninterrupted charge to 100% — realigns the fuel gauge to the actual usable voltage window of the new cell. After calibration, the shutdown point should track below 5%.