Google Pixel 4 G020I-B Replacement Battery 3.85V 2500mAh

Google Pixel 4 / G020M — 3.85V Li-Polymer Replacement Battery (G020I-B)

This is a 3.85V, 2500mAh Li-Polymer battery for the Google Pixel 4 and G020M. It replaces the original G020I-B cell when the phone no longer holds a charge through the day or fails to power on entirely. Capacity is rated at 9.63Wh and matches the original cell footprint at 86.62 × 70.72 × 4.72mm.

• Pixel 4 and G020M compatibility: Both the standard Pixel 4 and G020M share the same battery bay dimensions, connector pinout, and BMS handshake protocol — one cell covers both variants without modification.
• Bench tested on actual hardware: We ran this cell through the Pixel 4's charge IC and BMS. The protection circuit responded correctly to cutoff thresholds, and the fuel gauge IC accepted the cell without triggering a fault state.
• Fuel gauge recalibration on first use: After fitting this cell, disable fast charging and run one full discharge down to automatic shutdown, then charge to 100% on standard power. This gives the coulomb counter a clean baseline against the new cell's discharge curve before any fast-charge current is applied.

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

The Pixel 4's fuel gauge IC holds a learned discharge curve from the original cell. When a new cell goes in, that stored curve no longer matches the actual voltage-versus-capacity profile. At around 20–30% reported charge, the real cell voltage drops below the modem and display load threshold — the phone cuts power before the gauge catches up. One full discharge-recharge cycle on standard charging lets the coulomb counter relearn the curve and eliminates most premature shutdowns. If the problem persists after two full cycles, check that the battery connector is fully seated and read 3.85V at rest with a multimeter.

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

On first connection after a cell swap, the Pixel 4's charge IC performs a brief handshake with the battery BMS before negotiating USB-PD fast charge. If the BMS hasn't completed its initialisation — common when the cell has been in storage — the charge IC defaults to slow 5V charging as a fallback. Allow the first charge to complete fully at the slow rate without interrupting it. On the second cycle, fast charging typically resumes once the BMS has logged a complete charge event. Verify the charger output is rated at 18W or above and that the cable supports USB-PD — a standard USB-A cable bypasses the protocol entirely.