Samsung SGH-M188 Replacement Battery 3.7V 1150mAh Li-ion

Samsung SGH-M188 / SGH-M100 — 3.7V Li-ion Replacement Battery

This is a 3.7V, 1150mAh Li-ion cell built to restore power to the Samsung SGH-M188 and SGH-M100 flip phones. Both models share the same battery bay dimensions and charge circuit requirements. Capacity is 4.26Wh — matching the original cell specification.

• SGH-M188 and SGH-M100 compatibility: These two models use the same physical battery format, voltage rail, and charge termination logic. One cell fits both without modification to the contacts or compartment.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the SGH-M188. The BMS accepted charge termination correctly and held voltage through a full discharge without unexpected cutoff at mid-range state of charge.
• Fuel gauge recalibration on first cycle: After installing this cell, run one complete discharge down to automatic shutdown, then charge uninterrupted to 100% before normal use. The phone's fuel gauge IC was calibrated to your old cell's discharge curve — skipping this step causes the percentage counter to jump or read inaccurately for the first several cycles.

Why the SGH-M188 shuts down suddenly at 20–30% remaining

An aged cell develops high internal impedance. Under the brief current spikes from the RF transmitter during a call or an SMS burst, voltage drops sharply — fast enough to trip the low-voltage cutoff in the protection circuit even when the displayed percentage looks healthy. The fuel gauge is reading stored charge, not instantaneous voltage under load. Replacing the cell removes the impedance source; the shutdowns stop once the new cell's lower internal resistance keeps voltage stable during those peaks.

Battery percentage jumping erratically after cell swap

The SGH-M188 uses a simple coulomb-counting fuel gauge that builds its reference model from observed charge and discharge cycles. When a new cell goes in, the stored model no longer matches the actual discharge curve of the fresh cell — capacity and endpoint voltage have both changed. This mismatch causes the displayed percentage to jump, stall, or drop suddenly in the first few cycles. One full uninterrupted discharge to cutoff followed by a complete charge to 100% resets the reference model. After two or three cycles the percentage reading stabilises.