T-Mobile Galaxy S2 EB-L1D7IBA Replacement Battery 3.7V 3400mAh

T-Mobile Galaxy S2 — 3.7V Li-ion Replacement Battery (EB-L1D7IBA)

This is a 3.7V, 3400mAh Li-ion replacement battery for the T-Mobile Galaxy S2 (Galaxy S II). It carries OEM part number EB-L1D7IBA and slots directly into the standard battery compartment. It powers the processor, display, modem, and all onboard functions.

• Galaxy S2 platform fit: The Galaxy S2 and Galaxy S II share the same battery bay dimensions, connector pinout, and BMS handshake protocol. One cell covers both variants without modification.
• Bench tested on actual hardware: We ran this cell through charge and discharge cycles on a Galaxy S2 unit. The BMS accepted the charge IC handshake on the first cycle, and the protection circuit tripped correctly at the low-voltage cutoff threshold.
• Fuel gauge recalibration on first use: After installation, disable fast charging and run one full discharge-charge cycle at standard current. This lets the fuel gauge IC map the new cell's discharge curve before high-current charging is applied to an uncalibrated cell.

Sudden shutdown at 20–30% on the Galaxy S2

This happens when the cell cannot sustain voltage under high-current load — typically when the modem transmits or the screen runs at full brightness. The fuel gauge IC reads a nominal state of charge, but the cell voltage collapses under load before the gauge catches up. It is not a fault with the replacement cell itself — it means the fuel gauge IC is still calibrated to the old, degraded cell curve. Run two full discharge-charge cycles to let the coulomb counter recalibrate. After that, shutdowns below 20% should stop.

Phone shows incorrect battery percentage after cell swap

The Galaxy S2's fuel gauge IC stores a learned discharge curve from the previous cell. When a new cell goes in, the coulomb counter starts tracking against data that no longer matches the actual cell chemistry. This causes the percentage to read high, drop suddenly, or jump erratically. The fix is one complete discharge — down to automatic shutdown — followed by a full uninterrupted charge to 100%. After that cycle, the fuel gauge IC resets its baseline to the new cell and percentage reporting stabilises.