HTC One A9s Replacement Battery 3.85V 2300mAh B2PWD100

HTC One A9s — 3.85V Li-Polymer Replacement Battery (B2PWD100)

This 3.85V, 2300mAh Li-Polymer cell replaces the original battery in the HTC One A9s, One A9s LTE, and One A9s TD-LTE. It fits using OEM part references B2PWD100 and 35H00259-00M. Capacity matches the factory specification at 8.86Wh.

• One A9s variant coverage: The standard A9s, LTE, and TD-LTE variants all use the same battery bay geometry, connector pinout, and BMS handshake — one cell fits the full lineup without modification.
• Bench tested on actual hardware: We ran this cell through charge and discharge cycles on an A9s unit. The BMS accepted charge current correctly, thermal reporting stayed within normal range, and the fuel gauge IC initialised without error flags.
• First-cycle calibration tip: After installation, disable fast charging for one complete discharge-charge cycle. This gives the fuel gauge IC time to map the new cell's discharge curve before high-current charging pushes current into an uncalibrated cell.

Why the One A9s reports wrong battery percentage after a cell swap

The A9s uses a coulomb counter tied to a learned discharge curve from the original cell. When a new cell goes in, that learned curve no longer matches actual cell chemistry. The fuel gauge IC keeps referencing old data, so percentage readings drift — sometimes badly. One full discharge to shutdown followed by an uninterrupted charge to 100% forces the IC to rebuild its reference table against the new cell.

Sudden shutdown at 20–30% on the replacement cell

This happens when the cell voltage drops sharply under high load — modem transmit bursts or display brightness spikes — faster than the fuel gauge IC predicted. The phone interprets the voltage cliff as a hard cutoff and shuts down even though the reported percentage looks safe. It is not a faulty cell; it is the IC still calibrating to the new cell's internal resistance profile. After two or three full discharge-charge cycles the shutdowns stop. If they continue past three cycles, check resting voltage with a meter — it should read above 3.85V at a reported 50%.