Google Pixel Watch 2 GQ57S Compatible Battery 3.89V 4940mAh

Google Pixel 9 Pro XL / GQ57S — 3.89V Li-Polymer Replacement Battery (G949-01033-00)

This 3.89V, 4940mAh Li-Polymer battery fits the Google Pixel 9 Pro XL and GQ57S / GZC4K variants. It replaces a degraded or failed original cell restoring power to the display, processor, modem, and connectivity stack. Capacity figure is 19.22Wh as measured from product data — not an estimate.

• GQ57S and GZC4K platform fit: Both model codes share the same battery bay geometry, connector pinout, and BMS handshake protocol on the Pixel 9 Pro XL platform — the same cell services the voltage rail across all three identifiers without modification.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on a Pixel 9 Pro XL unit. The BMS accepted the new cell, completed a full charge cycle without thermal cutoff, and the charge IC reported correct termination voltage at 4.40V.
• Fuel gauge recalibration on first cycle: On first use after installation, disable fast charging and run one complete discharge-charge cycle at standard rate. This lets the fuel gauge IC map the new cell's discharge curve before the coulomb counter locks in its reference points — skipping this step causes erratic percentage reporting.

Sudden shutdown at 20–30% on the Pixel 9 Pro XL after a cell swap

A new Li-Polymer cell has a slightly different internal resistance profile than the aged cell the fuel gauge IC was calibrated against. Under high-current loads — 5G modem activity, sustained screen brightness, or simultaneous GPS use — the cell voltage can drop sharply below the BMS cutoff threshold even when the reported percentage still looks safe. The phone reads the voltage cliff as a critical low and shuts down immediately. One full unconstrained discharge-charge cycle resets the coulomb counter reference and resolves this in most cases.

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

After a cell swap, the charge IC on the Pixel 9 Pro XL runs an initial impedance check on the new cell before negotiating high-current USB-PD protocols. If the cell's internal resistance reads outside the expected window on the first cycle, the IC defaults to standard 5W charging as a protective measure. This is not a fault in the battery or the charger — it is the charge controller behaving correctly with an uncalibrated cell. Complete one full standard-rate charge cycle first, then reconnect a USB-PD charger; fast charge resumes once the IC accepts the cell's resistance profile at 9V / 2A or higher.