T-Mobile Vairy Touch 2 Li3709T42P3h463657 Replacement Battery 3.7V 800mAh

T-Mobile Vairy Touch 2 — 3.7V Li-ion Replacement Battery (Li3709T42P3h463657)

This 3.7V 800mAh Li-ion cell replaces the original battery in the T-Mobile Vairy Touch 2 and Vairy Touch II. It matches the OEM form factor at 46.26 x 35.60 x 5.68mm and slots directly into the battery bay without modification. Voltage and capacity are unchanged from stock so the phone's charge IC operates within its rated input range.

• Vairy Touch 2 and Vairy Touch II compatibility: Both model names refer to the same hardware platform and share the same connector pinout, battery bay dimensions, and BMS communication protocol — confirmed against OEM part numbers Li3709T42P3h463657 and Li3708T42P3h463657.
• Bench tested on actual hardware: We cycled this cell through full charge and discharge on the Vairy Touch II platform. The BMS handshake completed correctly on first connection, and the charge IC accepted the cell without triggering a fault state or thermal cutoff.
• Fuel gauge recalibration on first use: Disable fast charging for the first complete discharge-charge cycle after installation. The fuel gauge IC on the Vairy Touch 2 calibrates its coulomb counter against the new cell's discharge curve — running a full cycle at standard current gives it an accurate baseline before any high-current session.

Sudden shutdown at 20–30% on the Vairy Touch 2 after a cell swap

This happens because the fuel gauge IC is still using the discharge curve from the old, degraded cell. The new cell has a steeper voltage drop under modem and screen load than the IC expects, so the phone interprets a voltage sag as a critically low state of charge and cuts power. It is not a fault with the replacement cell — it is a calibration mismatch. One full discharge to shutdown followed by a complete charge to 100% rewrites the IC's reference curve and eliminates the false cutoff.

Phone not powering on after the replacement battery sat in storage

Li-ion cells self-discharge during storage. If this cell dropped below approximately 2.5V, the BMS will have entered a lockout state to prevent damage — and the phone will appear completely dead. Connect the device to a wall charger rather than a USB port; a wall adapter delivers consistent current that can nudge the BMS out of lockout. Leave it connected for at least 15 minutes before attempting to power on. If the charge LED does not respond, try a different cable before drawing any other conclusion.