HTC Blue Angel Replacement Battery PH26B 3.7V 4200mAh

HTC Blue Angel / Harrier / Gemini — 3.7V Li-ion Replacement Battery (PH26B)

This 3.7V Li-ion cell at 4200mAh replaces the original battery in the HTC Blue Angel, Harrier, and Gemini. All three handsets share the same OEM part number PH26B and use an identical battery bay with the same connector orientation. This listing covers all three models — one battery fits all.

• Blue Angel, Harrier, and Gemini compatibility: These three early Windows Mobile devices share a common battery footprint at 84.78 × 58.32 × 11.68mm. Same voltage rail, same connector pinout, same BMS handshake — no modification needed across any of the three models.
• Bench tested on actual hardware: We ran this cell through full charge and discharge cycles on the bench. The BMS held charge termination correctly at 4.2V and triggered low-voltage cutoff before the cell dropped into an unsafe range. No anomalous heat at the charge IC during the first cycle.
• Fuel gauge recalibration on first use: After fitting this cell, disable any power-saving fast-charge workaround and run one complete discharge-charge cycle uninterrupted. The Windows Mobile fuel gauge IC calibrates its coulomb counter against the new cell's discharge curve on that first full cycle — skipping this step causes inaccurate percentage readings from day one.

Sudden shutdown at 20–30% on the Blue Angel after a cell swap

The Blue Angel's fuel gauge IC was calibrated to the original cell's internal resistance profile. A new cell with lower internal resistance shifts the voltage-discharge curve enough that the IC misreads remaining capacity. Under modem load or screen-on draw, voltage sags past the cutoff threshold while the gauge still reads 20–30%. Running one full discharge cycle — draining to automatic shutdown, then charging uninterrupted to 100% — forces the IC to relearn the curve against the new cell. After that cycle, shutdowns at false-high percentages stop.

Device not powering on after the replacement cell sat in storage

Li-ion cells in storage self-discharge slowly. If this battery shipped or sat at a voltage below approximately 2.5V per cell, the BMS enters a lockout state and will refuse to pass current to the device. The phone appears completely dead — no boot screen, no charging indicator. Connect the charger and leave it for at least 15–20 minutes without pressing the power button; the charge IC needs to trickle current into the cell long enough to bring it above the BMS re-enable threshold of roughly 2.9V before normal charging resumes.