LG GW820 Replacement Battery SBPP0027401 3.7V 1000mAh

LG GW820 / eXpo — 3.7V Li-ion Replacement Battery (SBPP0027401 / LGIP-400N)

This is a 3.7V, 1000mAh Li-ion cell that replaces the original battery in the LG GW820, eXpo GW820, GW825, GW825 IQ, and related models. It ships at a partial state of charge and requires one full discharge-charge cycle before the fuel gauge IC reads accurately. Capacity is 3.7Wh — identical to the OEM specification.

• GW820 / GW825 platform fit: These models share the same battery bay dimensions, connector pinout, and 3.7V voltage rail. The BMS handshake protocol is consistent across the GW820 and GW825 variants, so this cell communicates with the charge IC without modification.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on a GW820 unit, monitoring BMS cutoff thresholds at both ends of the voltage window. The protection circuit engaged correctly at low-voltage cutoff and did not trip under normal screen and modem load.
• Fuel gauge recalibration on first use: After installation, run the battery from 100% down to automatic shutdown, then charge uninterrupted to full before using the device normally. The GW820's fuel gauge IC maps its coulomb counter against this first full cycle — skipping it causes percentage jumps for the first several days of use.

Sudden shutdown at 20–30% on the LG GW820 after a cell swap

The GW820's fuel gauge IC stores a discharge curve calibrated to the original cell's internal resistance profile. A new cell has a different impedance, so the IC miscalculates the remaining voltage window and triggers shutdown before the actual cell is depleted. This is not a defect in the replacement cell — it is a calibration lag. One complete discharge-charge cycle resets the coulomb counter and aligns the stored curve to the new cell. After that cycle, shutdown behaviour at low charge returns to normal.

Device not powering on after the replacement cell sat in storage

Li-ion cells self-discharge during storage. If the cell drops below approximately 2.5V per cell, the BMS locks out charging as a protection measure and the phone shows no response on the charge cable. Connect the phone to a wall adapter — not a USB port — and leave it for 15–30 minutes without pressing the power button. The charge IC on the GW820 sends a trickle current that slowly recovers the cell voltage above the BMS re-enable threshold, typically around 2.9V, at which point normal charging resumes.