O2 XDA Mini s Replacement Battery 3.7V 2350mAh 35H00062-00M

O2 XDA Mini s / XDA Mini Pro — 3.7V Li-ion Replacement Battery (35H00062-00M)

This 3.7V Li-ion cell replaces the original 35H00062-00M battery in the O2 XDA Mini s and XDA Mini Pro Windows Mobile smartphones. Capacity is 2350mAh (8.7Wh), matching the original power rail these handsets were built around. Mid-2000s pocket PC phones are notoriously hard to source cells for — this unit uses the correct pin-out and connector for both models.

• XDA Mini s and Mini Pro compatibility: Both handsets share the same battery bay dimensions, voltage rail, and connector orientation. The BMS on this cell communicates over the same three-contact interface the charging IC on both boards expects — no pin adapter or modification needed.
• Bench tested on actual hardware: We cycled this cell on an XDA Mini Pro board and confirmed the charge IC accepted the BMS handshake on the first connection. The protection circuit tripped correctly at the low-voltage cutoff threshold without triggering a hard board lockout.
• Fuel gauge recalibration on first use: After fitting this cell, run one complete discharge down to automatic shutdown, then charge uninterrupted to 100% before normal use. The XDA Mini s fuel gauge IC calibrates its coulomb counter against the discharge curve on the first full cycle — skip this and percentage readings will drift immediately.

Sudden shutdown at 20–30% on the XDA Mini s after a cell replacement

The XDA Mini s uses a simple coulomb-counting fuel gauge that was calibrated to the original cell's discharge curve at the factory. A new cell with a steeper voltage drop under load — particularly when the GSM modem transmits — hits the low-voltage cutoff before the gauge reaches 0%. The board interprets this as a hard undervoltage event and shuts down immediately, even though the displayed percentage looks safe. One full discharge-charge cycle resets the gauge's reference points and moves the cutoff threshold back into alignment with the new cell.

Device not powering on after the replacement battery sat in storage

Li-ion cells self-discharge in storage, and if this battery dropped below approximately 2.5V per cell during warehousing or transit, the BMS will have entered a deep-discharge lockout state to prevent damage. Connecting the phone to a wall charger — not a PC USB port — delivers enough current to trip the BMS recovery circuit. Hold the charger connection for at least 15 minutes before attempting to power on; PC USB ports often cannot supply sufficient current to exit the lockout and the phone will appear completely dead until a wall adapter is used.