T-Mobile G2 BA S450 Replacement Battery 3.7V 1000mAh

T-Mobile G2 — 3.7V Li-ion Replacement Battery (BA S450)

This is a 3.7V, 1000mAh Li-ion replacement battery for the T-Mobile G2 smartphone. It replaces OEM part numbers BA S450, 35H00140-00M, and 35H00140-01M. Fit the G2 when the original cell no longer holds a usable charge through a normal day of calls, messaging, and standby.

• G2 battery bay fit: The G2 uses a removable 3.7V single-cell Li-ion pack with a five-pin connector. The BMS handshake on this pack matches the G2's charge IC, so the phone recognises the cell and passes the authentication check on boot.
• Bench tested on actual hardware: We ran this cell through full charge-discharge cycles on the G2 and confirmed the BMS reports state-of-charge correctly to the OS. Charge IC accepted the cell without triggering a safety cutoff.
• Fuel gauge recalibration on first use: On first use after installation, disable fast charging for one complete discharge-charge cycle. This lets the fuel gauge IC map the new cell's discharge curve before high-current charging pushes current into an uncalibrated cell — prevents erratic percentage readings from the first charge onward.

Sudden shutdown at 20–30% on the G2 after a cell swap

The G2's fuel gauge IC retains the discharge curve from the previous cell. When the curve doesn't match the new cell, the IC predicts a voltage floor that doesn't exist — the phone shuts down before the actual charge is depleted. This happens because the coulomb counter is calibrated to the old cell's internal resistance profile. One full discharge to automatic shutdown followed by a full charge resets the curve. After that cycle, the percentage reading stabilises and the early-shutdown behaviour stops.

G2 not powering on after the replacement battery sat in storage

Li-ion cells self-discharge in storage. If the cell dropped below 2.5V per cell, the BMS trips a lockout to prevent charging a deeply discharged cell at full current. Plugging into a wall charger and leaving it for 20–30 minutes without pressing the power button allows the charge IC to trickle-charge the cell back above the BMS recovery threshold, typically 2.9V. Once the cell clears that threshold, the BMS unlocks, the phone accepts a normal charge rate, and the device powers on.