T-Mobile myTouch HB5N1 Compatible Battery 3.7V 1800mAh

T-Mobile myTouch Q U8730 / U8680 — 3.7V Li-ion Replacement Battery (HB5N1)

This 3.7V, 1800mAh Li-ion cell replaces the OEM HB5N1 and HB5N1H batteries in the T-Mobile myTouch, myTouch Q, myTouch Q U8730, and myTouch U8680 smartphones. It slots directly into the same battery bay and connects to the same three-contact strip the original cell used. Capacity is rated at 6.66Wh.

• myTouch and myTouch Q platform fit: The U8680 and U8730 share the same battery cavity dimensions, connector pinout, and BMS handshake protocol — which is why one cell covers both boards. The HB5N1H is a minor hardware revision of the HB5N1 and uses the same communication lines to the charge IC.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on a myTouch Q board and confirmed the BMS accepted the cell, reported state-of-charge to the OS, and did not trigger an overcurrent fault during the initial charge ramp.
• Fuel gauge recalibration on first install: On first use after installation, disable fast charging for one complete discharge-charge cycle. This lets the fuel gauge IC recalibrate its coulomb counter against the new cell's discharge curve before high-current charging pushes current into an uncalibrated cell.

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

This is a voltage cliff problem, not a capacity problem. Under modem transmit load or screen brightness peaks, the cell voltage drops sharply below the threshold the phone's power IC expects. The OS still shows 20–30% because the fuel gauge IC hasn't recalibrated to the new cell's discharge curve yet. Run one full discharge down to automatic shutdown, then charge uninterrupted to 100% — after that cycle, the coulomb counter realigns and the shutdowns stop.

Phone reporting wrong battery percentage after installing the HB5N1

The fuel gauge IC on the myTouch stores a learned discharge curve from the old cell. When a new cell goes in, that stored curve no longer matches the actual voltage-to-capacity relationship of the fresh cell. The result is percentage readings that jump erratically or plateau well above zero before shutdown. Force a full recalibration cycle: drain the phone to automatic power-off, then charge to 100% with the screen off. The fuel gauge IC will rewrite its reference curve against the new cell at approximately 3.0V at cutoff and 4.2V at full charge.