B0PAG100 HTC Butterfly 2 Replacement Battery 3.85V 2600mAh

HTC Butterfly 2 / B810X / HTL23 — 3.85V Li-Polymer Replacement Battery (B0PAG100)

This is a 3.85V, 2600mAh (10.01Wh) Li-Polymer cell for the HTC Butterfly 2, B810X, and HTL23 smartphones. It replaces OEM part numbers B0PAG100, BOPAG100, and 35H00223-00M. Fit the cell when the original no longer holds a charge or causes unexpected shutdowns mid-use.

• Butterfly 2, B810X, and HTL23 compatibility: All three models share the same battery bay geometry, connector pinout, and BMS communication protocol — the fuel gauge IC on each handset reads the same cell chemistry and reports state-of-charge using the same coulomb-counter calibration curve.
• Bench tested on actual hardware: We cycled this cell through a full discharge and charge sequence on a B810X, confirming the BMS accepted the cell without triggering an overcurrent or thermal cutoff fault, and that the charge IC ramped to the correct 4.35V termination voltage.
• First-cycle fuel gauge reset: On first use after installation, disable fast charging and run one complete discharge-to-charge cycle. This lets the fuel gauge IC recalibrate its coulomb counter against the new cell's discharge curve before high-current charging is introduced to an uncalibrated cell.

Sudden shutdown at 20–30% on the Butterfly 2 after a cell swap

The Butterfly 2's fuel gauge IC retains the discharge curve from the old, degraded cell after a swap. When the new cell hits a voltage region the IC hasn't mapped, the system reads the remaining charge as zero and cuts power — even though usable capacity is still present. The fix is one full uninterrupted discharge to automatic shutdown, followed by a full charge to 100% without interruption. After that single cycle, the coulomb counter recalibrates and percentage readings stabilise across the full range.

Phone warm near the battery bay on the first charge after replacement

A new high-impedance Li-Polymer cell generates more heat than a worn cell during the initial charge cycle because internal resistance is briefly elevated before the cell's electrolyte fully wets the electrode surfaces. The charge IC on the Butterfly 2 does not reduce current for this condition on its own. Keep the phone out of a case for the first full charge and place it on a hard, flat surface — this is enough to dissipate the heat. By the second charge cycle, impedance drops and warmth returns to normal levels.