Google Pixel 4 XL G020J-B Replacement Battery 3.85V 3600mAh

Google Pixel 4 XL — 3.85V Li-Polymer Replacement Battery (G020J-B)

This 3.85V, 3600mAh Li-Polymer battery replaces the original G020J-B cell in the Google Pixel 4 XL (model G020P). It restores full smartphone operation — calls, camera, display, and background services — after the factory cell has degraded through charge cycles. Dimensions are 97.30 × 48.36 × 4.80mm, matching the original fitment.

• Pixel 4 XL and G020P compatibility: Both device variants use the same battery bay dimensions, voltage rail, and BMS connector pinout. One cell fits both without modification.
• Bench tested on actual hardware: We cycled this cell through the Pixel 4 XL's charge IC and confirmed the BMS handshake completes correctly. The protection circuit held cutoff at the expected low-voltage threshold without triggering a false over-current trip during screen-on modem load.
• Fuel gauge recalibration on first use: After installation, disable fast charging and run one complete discharge down to auto-shutdown, then charge to 100% on standard charging. This lets the Pixel's coulomb counter map its charge curve against the new cell before fast-charge current is applied to an uncalibrated cell.

Sudden shutdown at 20–30% on the Pixel 4 XL after a cell swap

The Pixel 4 XL's fuel gauge IC inherits the state-of-charge model from the previous cell. When a new cell arrives with a different discharge curve, the IC misjudges the remaining capacity at the low end. Under modem or display load, the cell voltage drops sharply at that threshold and the phone cuts out before the OS can issue a low-battery warning. One full discharge-charge cycle forces the coulomb counter to relearn the new cell's actual voltage cliff, typically around 3.4–3.5V under load.

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

On the first charge after installation, the Pixel 4 XL's charge IC may default to trickle or standard 5V charging rather than negotiating USB-PD fast charge with the charger. This happens because the BMS on the new cell starts with no charge history and some charge controllers hold back high-current delivery until one baseline cycle completes. Plug into a genuine 18W USB-PD charger after the first full cycle and the fast-charge handshake should negotiate normally. If fast charge still doesn't appear in Battery settings, confirm the charger output with a USB meter — minimum 9V/2A is required.