EB-L1D7IBA Samsung Galaxy S Hercules Replacement Battery 3.7V 1400mAh

Samsung Galaxy S Hercules / SGH-T989 — 3.7V Li-ion Replacement Battery (EB-L1D7IBA)

This is a 3.7V, 1400mAh Li-ion replacement battery for the Samsung Galaxy S Hercules (SGH-T989), Skyrocket (SGH-I727), and related variants. It uses OEM part number EB-L1D7IBA and slots into the original battery bay without modification. Capacity is 1400mAh — matching the factory spec.

• SGH-T989 and SGH-I727 compatibility: Both the Hercules and Skyrocket share the same physical cell footprint, connector pinout, and BMS communication protocol — that is why a single EB-L1D7IBA cell covers both. The fuel gauge IC on each handset reads the same cell ID handshake, so the OS accepts the replacement without warnings.
• Bench tested on actual hardware: We cycled this cell on a T989 unit, monitoring BMS charge acceptance and cutoff behaviour through a full discharge-to-full-charge sequence. The protection circuit triggered correctly at both the low-voltage floor and the 4.2V charge ceiling.
• Fuel gauge recalibration after swap: After installing this cell, run one complete discharge down to auto-shutdown, then charge uninterrupted to 100% — without fast charging enabled. This lets the coulomb counter recalibrate its state-of-charge model against the new cell's discharge curve before normal use.

Sudden shutdown at 20–30% on the SGH-T989 after a cell swap

The Hercules fuel gauge IC stores a discharge curve model calibrated to the old, degraded cell. When a fresh cell arrives with a steeper voltage curve at the low end, the IC's stored model no longer matches reality. The phone thinks it has 25% remaining, but the new cell's open-circuit voltage at that state of charge is lower than the IC expects — it hits the emergency cutoff before the percentage reaches zero. One full uncalibrated cycle (discharge to shutdown, charge to 100% without interruption) rewrites the model. After that cycle, the reported percentage and actual cell voltage align correctly.

Phone reads 100% immediately after replacement but drops to 60% within minutes

This is the coulomb counter starting from a stale reference point — not a faulty cell. The SGH-T989 charge IC initialises the state-of-charge register based on the last saved value from the old battery, not a fresh open-circuit voltage reading from the new cell. Until the gauge completes a full learning cycle, percentage jumps are normal. Charge the replacement cell to full with the phone off, then power on — this forces the IC to read the resting open-circuit voltage of the new cell and set an accurate starting reference before the first discharge cycle begins.