About this replacement
Google Pixel 9 Pro XL — 3.9V Li-Polymer Replacement Battery (G949-00975-00)
This 3.9V, 4550mAh lithium-polymer cell replaces the factory battery in the Google Pixel 9 Pro XL (GEC77) and related Pixel 9 series models including GR83Y and GWVK6. It restores full device operation — calls, apps, camera, and background services. Capacity figures come from product data, not third-party estimates.
- Pixel 9 series platform fit: The GEC77, GR83Y, and GWVK6 share the same battery bay geometry, connector pinout, and BMS communication protocol. One cell covers the full Pixel 9 lineup using this form factor without modification.
- Bench tested on actual hardware: We ran this cell through full charge and discharge cycles on Pixel 9 hardware. The BMS handshake completed correctly, charge IC accepted the cell without fault codes, and voltage held steady under simultaneous modem and display load.
- Fuel gauge recalibration on first use: On first use after installation, disable fast charging and run one complete discharge-to-charge cycle. This lets the fuel gauge IC map its coulomb counter against the new cell's actual discharge curve before high-current charging begins.
Sudden shutdown at 20–30% on the Pixel 9 after a cell swap
The Pixel 9's fuel gauge IC stores a discharge model calibrated to the original cell. A new cell has a different internal resistance profile, so the IC misreads remaining voltage headroom. When the modem fires a high-current burst or the display ramps brightness, the new cell's voltage dips below the shutdown threshold even though the reported percentage looks safe. One full slow-charge cycle allows the coulomb counter to resync against the actual cell curve and eliminates most of these premature shutdowns.
USB-PD fast charge not activating on the first cycle after replacement
After a cell swap, the Pixel 9's charge IC sometimes refuses to negotiate USB-PD fast charging on the first cycle. The charge IC performs a safety handshake with the new BMS before unlocking higher current — if the BMS hasn't completed its first full initialisation, the IC falls back to standard 5V charging. Plug in using the standard charger, allow a full charge to 100% without interruption, then reconnect. Fast charge typically activates from the second cycle onward once BMS initialisation is complete.