O2 XDA Denim Replacement Battery 3.7V 1200mAh Li-ion

O2 XDA Denim — 3.7V Li-ion Replacement Battery (AZK40-HEL090-ZOR)

This is a 3.7V, 1200mAh Li-ion replacement battery for the O2 XDA Denim Windows Mobile smartphone. It slots into the original battery compartment and reconnects to the device's charge IC using the same connector arrangement as the factory cell. Capacity figure is 1200mAh as specified in the product data.

• XDA Denim platform fit: The XDA Denim uses a single-cell Li-ion pack at 3.7V nominal. This replacement matches that voltage rail and the physical footprint — 65.25 × 38.84 × 5.64mm — so it seats correctly without pressure on the rear cover.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the XDA Denim platform. The BMS handshake completed on first connection, and the charge IC accepted the cell without faulting or triggering a protection cutoff.
• Fuel gauge recalibration on first cycle: After fitting this replacement, run one full discharge down to automatic device shutdown, then charge uninterrupted to 100% before use. The XDA Denim's fuel gauge IC was calibrated to the old cell's discharge curve — one complete cycle resets it to the new cell so percentage readings stay accurate.

Why the XDA Denim reports wrong battery percentage after a cell swap

The XDA Denim tracks charge state using a fuel gauge IC that builds its model from previous discharge cycles. When the old cell is removed, that learned curve stays in the IC but no longer matches the new cell's actual chemistry and capacity. The gauge then reads percentage against the wrong reference, so the number shown can be off by 10–20%. One full discharge-to-shutdown cycle followed by a complete charge resets the coulomb counter and forces the IC to re-map against the replacement cell.

Sudden shutdown at 20–30% remaining on the XDA Denim

This happens when the cell voltage drops below the threshold the device needs to sustain the screen backlight and radio simultaneously — even though the fuel gauge still shows charge remaining. The gauge is reading stored energy, but the cell cannot hold voltage under that combined load. It is a voltage-sag failure, not a capacity failure. After the fuel gauge recalibrates over one full cycle, the cut-off point should move closer to 5–10%, where it belongs on a fresh 3.7V cell.