DIAM171 SoftBank X05HT Replacement Battery 3.7V 2400mAh

SoftBank X05HT / Touch Pro — 3.7V Li-ion Replacement Battery (DIAM171)

This is a 3.7V, 2400mAh Li-ion replacement battery for the SoftBank X05HT and HTC Touch Pro. It replaces OEM part numbers DIAM171, 35H00111-08M, and 35H00111-06M. The cell fits the original battery bay and connects to the device's existing charge circuit without modification.

• X05HT and Touch Pro compatibility: Both devices share the same physical battery bay, connector pinout, and BMS handshake protocol — the X05HT is the SoftBank-branded variant of the Touch Pro hardware platform, so one cell covers both.
• Bench tested on actual hardware: We ran this cell through charge and discharge cycles on Touch Pro hardware. The BMS accepted the cell without fault codes, and the charge IC stepped through trickle, constant-current, and constant-voltage phases normally.
• Fuel gauge recalibration on first install: After fitting this cell, disable any fast-charge accessory for the first full discharge-to-charge cycle. This allows the fuel gauge IC to map the new cell's discharge curve before high-current charging pushes current into an uncalibrated register — preventing erratic percentage readings from the first day.

Why the X05HT reports wrong battery percentage after a cell swap

The X05HT uses a fuel gauge IC that tracks charge state against a stored discharge curve from the original cell. When you fit a new cell, that stored curve no longer matches the actual voltage-to-capacity relationship of the replacement. The IC keeps reading against the old reference, so it may report 40% when the cell is at 20%. One complete slow discharge down to auto-shutoff, followed by a full charge, forces the IC to re-anchor its reference points against the new cell's actual curve.

Sudden shutdown at 20–30% on the replacement cell

This is a voltage cliff issue, not a capacity problem. Under the combined load of the WCDMA radio, screen backlight, and Windows Mobile background processes, the cell voltage drops sharply below the BMS cutoff threshold — even though the fuel gauge still shows charge remaining. The gauge reports stored coulombs, not real-time voltage. If shutdowns happen consistently above 20%, check that the cell voltage at shutdown is at or below 3.4V — if it is, the BMS is operating correctly and the fuel gauge simply needs a full recalibration cycle to align its readings with the new cell's actual voltage curve.