MetroPCS Activa 4G M920 Compatible Battery 3.7V 1400mAh

MetroPCS Activa 4G / M920 — 3.7V Li-ion Replacement Battery

This 3.7V, 1400mAh Li-ion cell replaces the original battery in the MetroPCS Activa 4G and M920 smartphones. It fits the same footprint at 53.80 × 42.30 × 5.60mm and restores power to the display, processor, and cellular radio. Use the capacity figure from the product data — 1400mAh / 5.18Wh — as your reference, not the original packaging.

• Activa 4G and M920 compatibility: Both models share the same battery bay dimensions, connector pinout, and 3.7V nominal voltage rail, so a single cell covers both variants without modification.
• Bench tested on actual hardware: We cycled this cell through full charge and discharge on the M920 platform and confirmed the BMS communicates state-of-charge data correctly to the OS throughout the curve — no false full readings at the top end.
• Fuel gauge recalibration on first install: On first use after installation, disable fast charging and run one complete discharge down to automatic shutoff, then charge uninterrupted to 100%. This lets the fuel gauge IC map its coulomb counter against the new cell's actual discharge curve before higher charge currents are applied.

Sudden shutdown at 20–30% on the Activa 4G after a cell swap

The Activa 4G's modem and display draw simultaneous current spikes during active calls or screen-on use. A fresh cell with an uncalibrated fuel gauge IC can report 25% remaining while the actual open-circuit voltage has already dropped toward 3.5V under load. The phone's protection circuit reads that voltage sag as a cutoff condition and shuts the device down — even though the percentage counter says charge remains. One full discharge-to-shutdown followed by a complete uninterrupted charge cycle recalibrates the coulomb counter and eliminates most of these premature cutoffs.

Percentage jumping erratically in the first two days after replacement

After a cell swap, the OS fuel gauge IC still holds the learned discharge curve of the old, degraded battery. It applies that curve to the new cell's voltage readings, producing jumps — commonly from 60% to 45% in minutes, or a sudden leap from 80% to 95%. This is a calibration gap, not a defective cell. Run the phone down to automatic shutoff, then charge to 100% without interruption. After that single cycle the gauge re-anchors its curve to the new cell's actual voltage profile and the percentage display stabilises.