BL-48LN T-Mobile myTouch Q Compatible Battery 3.7V 1200mAh

T-Mobile myTouch Q / myTouch Q 4G — 3.7V Li-ion Replacement Battery (BL-48LN)

This is a 3.7V, 1200mAh Li-ion replacement battery for the T-Mobile myTouch Q and myTouch Q 4G smartphones. It matches the OEM BL-48LN spec in voltage, capacity, and physical footprint — 52.00 x 50.00 x 5.20mm. Drop it in when the original cell can no longer hold a usable charge.

• myTouch Q and Q 4G compatibility: Both variants run the same 3.7V power rail and use the same BL-48LN connector pinout and BMS handshake. One cell fits both — no adapter, no modification needed.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the myTouch Q platform. The BMS accepted full charge termination correctly, and the protection circuit tripped as expected at low-voltage cutoff — no thermal events, no false cutoffs during normal load.
• Fuel gauge recalibration after install: On first use, disable fast charging if available and run one complete discharge-to-charge cycle at standard rate. This lets the fuel gauge IC map its coulomb counter against the new cell's actual discharge curve before the OS starts reporting accurate percentages.

Sudden shutdown at 20–30% on the myTouch Q after cell replacement

This happens because the fuel gauge IC is still using the discharge curve of the old, degraded cell. When the new cell hits a voltage region the IC misreads as 20–30% remaining, load from the modem or display pulls current the gauge didn't anticipate, and the BMS cuts power to protect the cell. The phone reads plenty of charge — but the cell voltage under load drops below the BMS cutoff threshold. One full discharge cycle, down to automatic shutdown and back to 100%, forces the coulomb counter to recalibrate against the new cell's actual voltage curve. After that cycle, percentage reporting stabilises and the early shutdowns stop.

Device won't power on after the replacement battery sat in storage

Li-ion cells self-discharge in storage. If the BL-48LN cell dropped below approximately 2.5V per cell before installation, the BMS enters lockout mode and blocks all current flow to protect against unsafe charging of a deeply discharged cell. The phone will show nothing — no charge indicator, no boot screen. Connect the phone to a wall charger rather than a PC USB port, which delivers lower current. Leave it connected for 15–30 minutes without pressing any buttons; the charge IC will trickle current into the cell until voltage climbs back above the BMS recovery threshold, typically around 3.0V, at which point the BMS unlocks and normal charging resumes.