O2 XDA Argon 3.7V Replacement Battery 35H00077-00M 1250mAh

O2 XDA Argon — 3.7V Li-Polymer Replacement Battery (35H00077-00M)

This is a 3.7V, 1250mAh Li-Polymer battery for the O2 XDA Argon smartphone. It replaces OEM part numbers 35H00077-00M, 35H00077-02M, and TRIN160. Swap it in when the original cell no longer holds charge or causes unexpected shutdowns.

• XDA Argon cell compatibility: The Argon uses a flat Li-Polymer cell with a specific connector pinout and BMS handshake. This replacement matches the 66.50 x 44.00 x 4.50mm footprint and voltage rail exactly, so the charge IC recognises the pack without throwing a fault.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the XDA Argon platform. The BMS accepted the pack on first connection, charge termination triggered correctly at 4.2V, and the protection circuit responded as expected to load cutoff.
• Fuel gauge recalibration on first use: After fitting this cell, disable fast charging and run one full discharge-charge cycle at standard rate. The fuel gauge IC on the Argon calibrates its coulomb counter against the new cell's discharge curve — skipping this step leads to erratic percentage readings for the first several days.

Sudden shutdown at 20–30% on the XDA Argon after a cell swap

This happens because the fuel gauge IC is still running the discharge curve from the old, degraded cell. The new cell has a steeper voltage slope near the bottom of its range, and the IC underestimates how close it is to the cutoff threshold. When the modem or screen pulls a short burst of high current, the cell voltage dips below 3.0V briefly, triggering an immediate hardware shutdown even though the displayed percentage looks safe. One full slow-rate discharge-charge cycle lets the coulomb counter re-anchor its curve to the new cell, and the false shutdowns stop.

Phone warm near the battery compartment during the first charge

A new Li-Polymer cell typically has higher internal impedance than a broken-in cell. On the first charge cycle, the charge IC pushes current into a cell that resists it more than expected, and that resistance converts some energy to heat. This is normal and settles after two or three cycles as the cell's impedance drops. If the device stays warm past the third full charge, check that the battery connector is fully seated — a partial connection increases contact resistance and compounds the heat.