LG G8S ThinQ Replacement Battery 3.85V 3450mAh BL-T43

LG G8S ThinQ — 3.85V Li-Polymer Replacement Battery (BL-T43)

This is a 3.85V, 3450mAh (13.28Wh) Li-Polymer cell that replaces the original BL-T43 battery in the LG G8S ThinQ. It fits the LMG810EA, G8S ThinQ Global, and G810 variants. Install it when the original cell no longer holds a charge or the phone shuts down unexpectedly under load.

• G8S ThinQ and G810 series fit: These models share the same battery bay dimensions, connector pinout, and BMS handshake protocol tied to the BL-T43 cell. The 74.10 × 65.90 × 4.00mm footprint matches the chassis cavity exactly, and the flex connector seats to the same board-side socket across all G810 variants.
• Bench tested on actual hardware: We ran this cell through charge and discharge cycles on a G8S ThinQ unit. The BMS accepted the charge IC handshake without error, voltage held stable across the discharge curve, and the protection circuit triggered correctly at the low-voltage cutoff threshold.
• Fuel gauge recalibration on first cycle: On first use after installation, disable fast charging and run one complete discharge-to-charge cycle at standard rate. 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 G8S ThinQ after a cell swap

This is a voltage cliff issue, not a defective cell. Under heavy load — active modem, display at full brightness, GPS — the new cell's internal resistance causes a brief voltage drop that the protection circuit reads as a low-voltage condition. The phone cuts power before the displayed percentage reaches zero. The fuel gauge IC is still calibrated to the old cell's curve, so the percentage shown does not reflect the actual state of charge in the new cell. Run two full discharge-charge cycles at standard charge rate, and the coulomb counter will relearn the new cell's capacity and cutoff behaviour. After calibration, shutdowns below 20% should stop.

USB-PD fast charge not activating on the first cycle after replacement

After a cell swap, the charge IC on the G8S ThinQ sometimes withholds fast charge negotiation on the first cycle. The controller checks cell impedance before stepping up current, and a new high-impedance cell can cause it to fall back to standard 5V charging. This is not a fault with the replacement cell or the charger. Charge the phone once at standard rate until full, then fast charging will engage normally on subsequent cycles once the controller has confirmed stable impedance readings.