Google Nexus One G20 Compatible Battery 3.7V 1600mAh

Google Nexus One G20 — 3.7V Li-ion Replacement Battery (BH39100)

This 3.7V, 1600mAh Li-ion cell replaces the original battery in the Google Nexus One (G20). It fits the slot directly and connects to the same three-pin contact strip the phone uses for charge reporting. Capacity is 1600mAh — matching OEM specification at 5.92Wh.

• G20 contact and BMS compatibility: The Nexus One uses a three-contact battery with a dedicated thermistor line the charge IC reads before allowing current in. This cell carries the matching NTC thermistor so the phone does not block charging on the first cycle.
• Bench tested on actual hardware: We cycled this cell on a Nexus One unit and confirmed the BMS handshake cleared on the first insertion, charge current ramped correctly through CC and CV phases, and the fuel gauge IC accepted the new cell without a forced reset.
• Fuel gauge recalibration on first use: After installation, run one complete discharge down to automatic shutdown, then charge to 100% uninterrupted before enabling fast charging. This gives the coulomb counter a full reference curve for the new cell and prevents erratic percentage readings in the first week of use.

Why the Nexus One reports wrong battery percentage after a cell swap

The Nexus One's fuel gauge IC builds its percentage estimate against a discharge curve stored from the previous cell. A new cell has a different internal resistance profile, so the stored curve no longer matches what the hardware measures. The IC compensates by jumping or freezing the percentage until it collects enough data. One full discharge-charge cycle without interruption resets the reference curve and the readout stabilises.

Sudden shutdown at 20–30% on the replacement cell

This happens when the modem or display draws a short burst of current and the cell voltage drops below the BMS cutoff threshold — even though the fuel gauge still shows charge remaining. The gauge is reading average voltage, not instantaneous sag. A fresh cell with an uncalibrated curve makes this worse in the first few cycles. After two full discharge-charge cycles the IC tightens its voltage floor estimate and shutdowns at that range stop. If they continue past three cycles, check the battery contacts are clean and seating flat — target resting voltage after full charge should read 4.18–4.20V at the contact strip.