About this replacement
Google Pixel 9 Pro Fold / Pixel 4a (GC15S) — 3.87V Li-Polymer Replacement Battery (GWRL2)
This is a 3.87V, 3050mAh (11.8Wh) Li-Polymer replacement cell for Google devices using OEM part number GWRL2. It fits the Pixel 4a (GC15S), GGH2X, and Pixel 9 Pro Fold. If your phone cuts out early, refuses to hold a charge, or won't power on at all, this cell replaces the degraded original.
- GC15S, GGH2X, and Pixel 9 Pro Fold compatibility: All three models share the GWRL2 connector pinout and BMS handshake protocol. The fuel gauge IC on each expects the same cell chemistry and voltage curve, so the replacement integrates without triggering a hardware fault.
- Bench tested on actual hardware: We cycled this cell through charge and discharge on a Pixel 4a unit. The BMS accepted the cell without error flags, the charge IC stepped through its CC/CV stages correctly, and USB-PD handshake completed normally after the first full cycle.
- First cycle after installation: Disable fast charging for one complete discharge-charge cycle after fitting this cell. The fuel gauge IC is still calibrated to the old cell's discharge curve — running a slow cycle first lets the coulomb counter reset against the new cell before fast charge pushes high current into an uncalibrated state.
Why the Pixel 9 Pro Fold drops dead at 20–30% after a cell swap
The Pixel 9 Pro Fold's power management IC tracks battery state using a coulomb counter seeded by the original cell's discharge curve. A new cell has lower internal impedance than a worn one, so the voltage cliff the software expects at low charge doesn't arrive at the same point. The phone interprets a mid-discharge voltage sag — triggered by the foldable display or modem load — as a sudden drop to 0% and shuts down. One full slow discharge-charge cycle forces the fuel gauge IC to relearn the new curve. After that cycle, shutdowns at 20–30% typically stop.
USB-PD fast charge not activating on first cycle after replacement
After fitting a new GWRL2 cell, some users find the phone charges slowly even on a USB-PD brick that worked fine before. The charge IC defaults to a low-current trickle profile when it can't confirm the cell's state of charge — this is a BMS protection behaviour, not a charger fault. The USB-PD handshake completes at the port level, but the charge IC limits current internally until it has logged one complete cycle. Let the phone discharge to below 10% and charge to 100% once at standard speed, then reconnect the fast charger — it should negotiate full wattage from that point.