NGM SOAP Replacement Battery 3.7V 900mAh Li-ion

NGM SOAP — 3.7V Li-ion Replacement Battery

This is a 3.7V, 900mAh Li-ion replacement battery for the NGM SOAP smartphone. It slots into the SOAP's battery bay and restores power to a handset that no longer holds a usable charge. Capacity is 3.33Wh, matching the original cell specification.

• NGM SOAP fit: The SOAP uses a compact 46.20 × 34.14 × 5.68mm cell at 3.7V nominal. This replacement matches those physical and electrical parameters — the connector orientation and BMS communication lines align with the SOAP's charge IC without modification.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the bench. The BMS initialised correctly, charge termination triggered at the expected cutoff voltage, and the protection circuit responded to simulated over-discharge conditions without latching into lockout.
• Fuel gauge recalibration on first install: On first use after fitting this cell, run one full discharge to auto-shutoff and then a full uninterrupted charge. The SOAP's fuel gauge IC was calibrated to the old cell's discharge curve — skipping this step leaves the coulomb counter reading against the wrong reference, which causes erratic percentage jumps.

Sudden shutdown at 20–30% on the NGM SOAP after a cell swap

This is a voltage cliff issue, not a capacity problem. At 20–30% state of charge, the modem radio or display draws a current spike the new cell briefly cannot sustain without its terminal voltage dropping below the BMS cutoff threshold. The protection circuit reads an undervoltage condition and shuts the phone down even though charge remains in the cell. One full discharge-charge cycle lets the fuel gauge IC map the actual discharge curve of the new cell, which corrects the cutoff point — after calibration, the SOAP should carry charge below 20% without tripping.

NGM SOAP showing wrong battery percentage after replacement

The SOAP's fuel gauge IC tracks charge using a coulomb counter referenced to the previous cell's internal resistance and capacity profile. Swap in a new cell and that reference is immediately wrong, so the displayed percentage drifts or jumps. This is not a fault with the replacement battery — it is a calibration lag in the phone's power management IC. Force a full discharge to automatic shutdown, then charge to 100% without interruption. After that single cycle the coulomb counter resets against the new cell's actual curve and percentage reporting stabilises.