35H00189-02M HTC One M8 Replacement Battery 3.8V 1950mAh

KDDI HTI13 / Valente WX — 3.8V Li-ion Replacement Battery (35H00189-02M)

This 3.8V, 1950mAh Li-ion cell replaces the original power unit in the KDDI HTI13, Valente WX, and ISW13HT — all HTC One M8 platform variants sold under the KDDI carrier label. It matches OEM part number 35H00189-02M and HTI13UAA. Physically, it measures 58.90 × 51.10 × 5.10mm, so it seats flush in the original battery bay without modification.

• HTI13 / Valente WX / ISW13HT platform: All three models share the same HTC One M8 mainboard layout, battery connector pinout, and BMS handshake protocol. A single cell spec covers all three variants — same voltage rail, same thermistor line, same mechanical footprint.
• Bench tested on actual hardware: We cycled this cell on an HTI13 unit and confirmed the BMS accepted the thermistor signal without fault codes. Charge IC entered CC/CV mode normally and the fuel gauge IC began tracking state-of-charge from the first cycle.
• Fuel gauge recalibration on first install: After fitting this cell, disable fast charging and run one full discharge-to-charge cycle before resuming normal use. This lets the fuel gauge IC map the new cell's discharge curve before high-current charging pushes into an uncalibrated state-of-charge register.

Why the HTI13 reports wrong battery percentage after a cell swap

The HTC One M8 platform uses a coulomb counter that builds its reference curve against the original cell over hundreds of cycles. When a new cell goes in, the stored curve no longer matches the actual discharge profile of the fresh cell. The fuel gauge IC reads voltage and current against stale data, so it reports inflated or erratic percentages until it relearns the curve. One complete discharge below 10% followed by a full charge to 100% resets the reference and brings the percentage display back into line.

Sudden shutdown at 20–30% charge remaining

This is a voltage-cliff failure: under heavy screen or modem load, the cell voltage drops faster than the fuel gauge IC predicts, crossing the protection threshold before the displayed percentage reaches zero. The BMS trips to prevent over-discharge, cutting power instantly. It is most common in the first few cycles before the coulomb counter recalibrates to the new cell. Run two full discharge-charge cycles and confirm the cell holds above 3.6V under load at the point where the phone previously shut down.