E-TEN P603 Replacement Battery 3.7V 2200mAh Li-ion

E-TEN P603 / P610 — 3.7V Li-ion Replacement Battery (4900156)

This 3.7V, 2200mAh Li-ion cell replaces OEM part 4900156 in the E-TEN P603 and P610 Windows Mobile smartphones. It restores power to devices where the original cell has degraded, lost capacity, or stopped holding a charge. Voltage and connector match the original spec.

• P603 and P610 shared platform: Both devices run on the same battery rail, use the same connector, and share the same BMS handshake protocol — one cell covers both models without modification.
• Bench tested on actual hardware: We cycled this cell through full charge and discharge on P603 hardware. The BMS accepted the cell without fault flags, and the charge IC completed a full CC/CV cycle to 4.2V.
• Fuel gauge recalibration on first use: On first use after installation, run one full discharge-to-charge cycle without interruption. This lets the fuel gauge IC map the new cell's discharge curve before it can report accurate percentages.

Sudden shutdown at 20–30% on the P603 after cell replacement

The P603's fuel gauge IC stores a discharge curve from the old, degraded cell. When a new higher-capacity cell is installed, the IC's voltage map no longer aligns with the new cell's actual cutoff behaviour. At 20–30% indicated charge, the new cell's voltage can drop sharply under modem or screen load — faster than the IC expects — triggering an emergency shutdown. One full uninterrupted discharge-to-charge cycle resets the coulomb counter and writes a fresh curve. After that cycle, the percentage readout and shutdown behaviour stabilise.

Phone warm near the battery compartment during first charge

A new cell starts with higher internal impedance than a cycled one. The charge IC pushes constant current into that higher impedance, generating more heat than usual in the first few charges. This is normal and reduces after two or three full cycles as impedance drops. If the device becomes too hot to hold comfortably, stop the charge, let it cool, and resume — do not leave it unattended until after the first three cycles confirm temperature stays within a normal range.