Google G6 BA S440 Replacement Battery 3.7V 1000mAh

Google Nexus One G6 — 3.7V Li-ion Replacement Battery (BA S440)

This is a 3.7V, 1000mAh Li-ion cell built to fit the Google Nexus One (G6). It replaces OEM part numbers BA S440, BB00100, and the 35H00127 series. Install it when the original cell no longer holds a usable charge or fails to power the device through a normal day.

• Nexus One G6 fit: The G6 uses a dedicated connector pinout and a BMS handshake tied to the 35H00127 cell family. This replacement matches that voltage rail and connector so the phone's charge IC recognises the cell and accepts current normally.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on G6-class hardware. The BMS held the 4.2V cutoff cleanly, the protection circuit tripped correctly on over-discharge, and the charge IC pulled steady current without thermal interrupts.
• Fuel gauge recalibration on first use: On the first cycle after installation, disable fast charging and run one full discharge down to automatic shutdown, then charge uninterrupted to 100%. This gives the fuel gauge IC one clean sweep to map the new cell's discharge curve before high-current charging is reintroduced.

Sudden shutdown at 20–30% on the Nexus One after a cell swap

The Nexus One's fuel gauge IC stores the old cell's discharge curve in memory. When a new cell is installed, the IC still references the degraded curve, so it predicts remaining capacity incorrectly. Under screen-on or modem load, the new cell's actual voltage can drop below the shutdown threshold before the OS registers it. One full uninterrupted discharge-to-shutdown and recharge cycle forces the coulomb counter to reset against the new cell's actual curve.

Phone feels warm near the battery during the first charge after replacement

A new cell arrives with higher internal impedance than a cell that has been cycled. The charge IC on the Nexus One pushes current at a fixed rate, and higher impedance means more energy is dissipated as heat during that first session. This is normal and typically settles after two to three full cycles as the cell's impedance drops. If warmth continues past the third cycle or the phone becomes hot to the touch, check that the battery connector is fully seated and making clean contact.