Google Pixel 5 GTB1F Replacement Battery 3.85V 3800mAh

Google Pixel 5 — 3.85V Li-Polymer Replacement Battery (GTB1F)

This is a 3800mAh Li-Polymer battery at 3.85V, built as a direct cell replacement for the Google Pixel 5 smartphone. It matches the original GTB1F specification in voltage, chemistry, and physical footprint — 97.85 × 44.70 × 5.20mm. Swap it in when the original cell no longer holds a usable charge across a full day.

• Pixel 5 cell compatibility: The Pixel 5 uses a single Li-Polymer pouch cell with a five-pin flex connector. Voltage matching at 3.85V nominal is critical — the charge IC on the Pixel 5 mainboard will not complete a charge cycle if the BMS reports an out-of-range cell voltage on first handshake.
• Bench tested on actual hardware: We ran this cell on a Pixel 5 mainboard and confirmed the BMS handshake completed on first boot, charge IC accepted the cell without an error state, and USB-PD fast charge activated after one conditioning cycle.
• Fuel gauge recalibration on first cycle: After installation, disable Adaptive Charging and fast charging in Battery Settings for the first complete discharge-charge cycle. This lets the Pixel 5 fuel gauge IC map the new cell's discharge curve before high-current charging pushes current into an uncalibrated cell — skipping this step is why percentage readings drift early.

Why the Pixel 5 shuts down suddenly at 20–30% after a cell swap

The Pixel 5 fuel gauge IC retains the discharge curve from the original aged cell. A new 3800mAh cell has a steeper voltage cliff at low state-of-charge than a worn cell does — so the IC underestimates remaining capacity until it recalibrates. Under modem load or screen-on draw, the cell voltage sags below the hardware cutoff threshold before the OS registers empty. One full discharge-charge cycle without fast charging forces the coulomb counter to resync against the new cell's actual curve and eliminates these early shutdowns.

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

On the first charge cycle after a cell swap, the Pixel 5 charge IC defaults to a low-current trickle mode while it verifies the new cell's BMS handshake parameters. USB-PD negotiation still occurs at the port level, but the charge IC gates high-current delivery until internal cell checks pass — this is normal behaviour, not a faulty battery or cable. If fast charge does not activate by the second charge cycle, check that the USB-C port is clean and try a certified 18W or higher USB-PD charger. Fast charge should engage fully once the cell reports a stable open-circuit voltage above 3.6V after a complete first cycle.