Samsung SGH-A100 Replacement Battery 3.7V 900mAh Li-ion

Samsung SGH-A100 Series — 3.7V Li-ion Replacement Battery

This is a 3.7V, 900mAh Li-ion battery for the Samsung SGH-A100, SGH-110, SGH-A188, and SCH-A120. It replaces the original cell when the existing battery no longer holds enough charge to get through a day of calls and standby. Capacity matches the stock specification at 900mAh (3.33Wh).

• SGH and SCH cross-platform fit: These Samsung models share the same battery bay geometry and voltage rail. The cell connector pinout and BMS handshake protocol are consistent across the SGH-A100, SGH-110, SGH-A188, and SCH-A120, so one cell fits the full group without modification.
• Bench tested on actual hardware: We cycled this cell through charge and full discharge on the SGH-A100 platform. The BMS accepted charge current without fault codes, hit full cutoff at 4.2V, and the protection circuit tripped correctly at the low-voltage threshold before cell damage could occur.
• Fuel gauge recalibration on first use: On first use after installation, run one complete discharge down to automatic shutdown, then charge uninterrupted to 100% before using the phone again. This gives the fuel gauge IC a full reference curve against the new cell so percentage readings stay accurate from day one.

Why the SGH-A100 reports wrong battery percentage after a cell swap

The SGH-A100 uses a fuel gauge IC that builds its capacity model from accumulated charge and discharge data on the original cell. When you swap to a new cell, the IC still references the old degraded discharge curve. Until it maps the new cell's actual voltage-to-capacity relationship, the percentage on screen is an estimate against the wrong baseline. One full discharge-to-shutdown followed by a complete uninterrupted charge corrects this — the IC rewrites its reference points against the new cell's actual curve. After that single cycle, percentage jumps and early shutoffs typically stop.

Sudden shutdown at 20–30% on the replacement cell

This happens because the phone's baseband radio and screen draw a burst of current that drops the cell voltage sharply at a certain state of charge. If the cell voltage dips below the BMS protection threshold — typically around 3.0V under load — the protection circuit cuts power instantly, even though the gauge was still showing 20–30%. On a freshly swapped cell that hasn't been calibrated, the fuel gauge doesn't know where the real voltage cliff sits. Run one full discharge cycle to let the IC find the actual low-voltage floor. After calibration, the phone should shut down gracefully near 5–7% rather than cutting out mid-use.