EB-L1D7IBA Galaxy S II 3.7V Compatible Battery 1400mAh

T-Mobile Galaxy S II SGH-T989 — 3.7V Li-ion Replacement Battery (EB-L1D7IBA)

This is a 3.7V, 1400mAh Li-ion replacement battery for the T-Mobile Galaxy S II and SGH-T989 smartphone. It replaces the original EB-L1D7IBA cell when the phone no longer holds adequate charge through a day of normal use. Dimensions are 56.80 × 50.50 × 6.00mm — a direct physical match to the stock battery bay.

• SGH-T989 and Galaxy S II 4G compatibility: Both variants run the same 3.7V power rail, use the same battery bay dimensions, and share the same three-contact connector pinout — one cell fits all three models listed.
• Bench tested on actual hardware: We cycled this cell through the SGH-T989's charge IC and confirmed the BMS communicates correctly at full charge termination. The board accepted the cell without flagging an authentication error or suppressing charge current.
• Fuel gauge recalibration on first cycle: On first use after installation, run one complete discharge-charge cycle before relying on the percentage readout. The Galaxy S II's fuel gauge IC was calibrated to the old cell's discharge curve — a full cycle lets it reset against this cell's actual capacity profile.

Why the SGH-T989 reports wrong battery percentage after a cell swap

The Galaxy S II uses a coulomb-counter-based fuel gauge IC that builds its percentage model from accumulated charge and discharge data on the original cell. When you swap the battery, the IC still holds the old cell's internal resistance and capacity curve in memory. It has not yet measured this cell's actual voltage-to-capacity relationship. Run the phone down to auto-shutdown, then charge uninterrupted to 100% — one full cycle resets the coulomb counter against real data from the new cell.

Sudden shutdown at 20–30% on the replacement cell

This is a voltage cliff issue, not a capacity problem. Under heavy modem or screen load, the cell voltage drops sharply at a certain state-of-charge — faster than the fuel gauge IC predicts — and the phone's protection circuit shuts down before the displayed percentage reaches zero. It happens most often on the first few cycles before the fuel gauge recalibrates. After two or three full discharge-charge cycles, the IC learns the new cell's voltage curve and the shutdowns stop. If they continue past five cycles, check that resting cell voltage at "30%" reads above 3.6V.