About this replacement
LG Optimus G Pro — 3.8V Li-ion Replacement Battery (BL-48TH)
This is a 3.8V, 3100mAh Li-ion replacement battery for the LG Optimus G Pro. It fits the E940, E980, and E977 model variants. The OEM part number is BL-48TH (also cross-referenced as EAC62058511).
- E940 / E980 / E977 compatibility: These variants share the same battery bay dimensions, connector pinout, and BMS handshake protocol — one cell fits all three without modification.
- Bench tested on actual hardware: We cycled this battery on the E940 and monitored the BMS through charge and load. The protection circuit responded correctly to cutoff at full charge and held voltage under screen and modem load without tripping.
- Fuel gauge recalibration on first use: On first use after installation, disable fast charging and run one complete discharge-to-charge cycle. The E940's fuel gauge IC calibrates against the cell's discharge curve — skipping this step leaves the coulomb counter reading the old cell's profile, which causes erratic percentage jumps early on.
Sudden shutdown at 20–30% on the Optimus G Pro after a cell swap
The E940 pulls heavy current when the modem is active and the screen is at full brightness. A new cell with an uncalibrated fuel gauge IC can show 25% remaining while the actual cell voltage has already dropped to the BMS cutoff threshold — around 3.0V under load. The phone interprets this as a hard shutdown, not a low-battery warning. One full discharge-charge cycle after installation lets the coulomb counter anchor to the new cell's actual voltage curve and fixes this.
OS percentage jumping erratically in the first two days after replacement
The Optimus G Pro's fuel gauge IC stores a learned discharge profile from the old cell. When a new cell goes in, the stored curve no longer matches the actual voltage-to-capacity relationship of the replacement. The OS reads the mismatch as unstable state-of-charge data, so the percentage display skips around. Drain the battery to below 5% until the phone shuts off, then charge uninterrupted to 100% — this forces the IC to write a fresh calibration baseline against the new cell.