Samsung Nexus S AB653850CA Replacement Battery 3.7V 2800mAh

Samsung Nexus S / Nexus S 4G — 3.7V Li-ion Replacement Battery (AB653850CA)

This is a 3.7V, 2800mAh Li-ion cell replacing the original AB653850CA in the Samsung Nexus S and Nexus S 4G. It fits GT-I9020 and GT-I9020T hardware directly. Slide the original out, drop this in — connector and form factor are a direct match at 51.68 × 41.50 × 12.51mm.

• GT-I9020 and GT-I9020T compatibility: Both the standard Nexus S and the 4G variant share the same battery bay dimensions, connector pinout, and BMS communication protocol — one cell fits both boards without modification.
• Bench tested on actual hardware: We ran charge-discharge cycles on a GT-I9020 board. The BMS accepted charge current without fault codes, and cell voltage held stable across the full discharge curve from 4.2V down to the 3.0V cutoff.
• Fuel gauge recalibration on first use: After fitting this cell, disable fast charging if available and run one full discharge-to-charge cycle before normal use. The Nexus S fuel gauge IC calibrates its coulomb counter against the actual cell discharge curve — skipping this step can cause the OS to report inaccurate percentages for the first several cycles.

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

The Nexus S uses a fuel gauge IC that tracks charge state against a stored discharge curve from the original cell. When a new cell goes in, that stored curve no longer matches actual cell behaviour, so the reported percentage drifts from reality. The fix is one complete discharge-charge cycle with the screen on at moderate brightness — this forces the coulomb counter to re-anchor against the new cell's actual voltage-to-capacity relationship. After that cycle, percentage accuracy returns to normal operating tolerance.

Sudden shutdown at 20–30% on the Nexus S

This happens when the cell voltage drops sharply under modem or display load — a voltage cliff the fuel gauge IC didn't predict because it was still calibrated to a degraded old cell. The Nexus S modem radio draws hard burst current, and if the cell can't hold voltage above the protection threshold during that burst, the BMS trips and the phone cuts out. Fitting a fresh cell resolves the capacity side, but the shutdowns won't stop until the fuel gauge IC recalibrates. Run one full cycle and check that resting voltage after a full charge reads 4.18–4.20V before trusting the percentage readout.