O2 XDA Graphite Replacement Battery SBP-02 3.7V 1100mAh

O2 XDA Graphite — 3.7V Li-ion Replacement Battery (SBP-02)

This is a 3.7V, 1100mAh Li-ion cell for the O2 XDA Graphite, a Windows Mobile PDA-smartphone from the mid-2000s. It replaces OEM part numbers SBP-02 and XP-07. If your XDA Graphite no longer holds a charge or fails to power on after years of storage, this cell addresses the root cause — an aged original cell that has degraded beyond recovery.

• XDA Graphite fitment: The XDA Graphite uses a single-cell 3.7V Li-ion pack with a proprietary connector. This replacement matches that connector pinout and BMS handshake, so the device recognises the cell and accepts charging without a firmware error.
• Bench tested on actual hardware: We ran this cell through charge and discharge cycles on a test rig. The BMS engaged at the correct cutoff voltages — 4.2V at full charge and 3.0V at low cutoff — and the protection circuit tripped correctly under simulated over-current conditions.
• Fuel gauge recalibration on first use: On first installation, run one complete discharge down to automatic shutdown, then charge uninterrupted to 100%. The XDA Graphite's fuel gauge IC was calibrated against the old degraded cell curve — this single full cycle resets the coulomb counter against the new cell's actual capacity.

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

The XDA Graphite tracks charge state using a fuel gauge IC that builds a discharge curve over time. When you swap in a new cell, that stored curve no longer matches the new cell's voltage-to-capacity profile. The device reads voltage and maps it against the old degraded curve, which causes it to report inflated or deflated percentages. One full discharge-to-shutdown followed by a full uninterrupted charge corrects this — the IC writes a new baseline against the replacement cell.

Sudden shutdown at 20–30% on the XDA Graphite after replacement

This happens because the fuel gauge IC is still using the old cell's discharge curve, so the displayed percentage does not reflect actual remaining capacity. When the modem or screen draws a burst of current, the cell voltage sags below the BMS cutoff threshold before the gauge reaches 0%. The device shuts down to protect the cell even though the screen shows charge remaining. Fix this by completing one full discharge-recharge cycle — the gauge recalibrates and the shutdowns stop once the coulomb counter is reset against the new cell.