MetroPCS LGMS840V Replacement Battery 3.7V 1200mAh

MetroPCS LGMS840V — 3.7V Li-ion 1200mAh Replacement Battery

This is a 3.7V Li-ion replacement battery rated at 1200mAh (4.44Wh) for the MetroPCS LG MS840V smartphone. It fits the LGMS840V directly, restoring power to calling, messaging, and app functions. Install it when the original cell no longer holds a charge or the phone shuts down unexpectedly.

• LGMS840V cell compatibility: The MS840V uses a 3.7V single-cell Li-ion pack with a connector and footprint matched to this form factor — 64.50 x 44.40 x 4.50mm. The BMS on this replacement communicates with the phone's charge IC using the same handshake as the factory cell.
• Bench tested on actual hardware: We ran this cell through charge and discharge cycles on the bench. The BMS held cutoff at the correct low-voltage threshold and accepted charge current without triggering a fault condition on the charge IC.
• Fuel gauge recalibration on first install: On first use after installation, disable fast charging and run one complete discharge-charge cycle. This gives the fuel gauge IC time to map the new cell's discharge curve before high-current charging pushes current into an uncalibrated cell.

Sudden shutdown at 20–30% on the LGMS840V after a cell swap

This is a voltage cliff issue, not a faulty cell. When the modem transmits or the screen runs at full brightness, current draw spikes sharply. A new cell that has not been calibrated may sag below the BMS cutoff threshold before the fuel gauge reports 0%. The phone interprets this as a hard shutdown, even though the percentage display showed headroom. One full slow discharge-charge cycle lets the coulomb counter learn the actual voltage-to-capacity relationship of the new cell and prevents early cutoff under load.

OS reporting wrong battery percentage after replacement

The fuel gauge IC on the LGMS840V stores a learned discharge curve from the original cell. When a new cell goes in, that stored curve no longer matches actual cell behaviour, so the percentage reading drifts or jumps. Drain the phone fully until it powers off, then charge uninterrupted to 100% without interruption. After one complete cycle, the coulomb counter resets its baseline and percentage accuracy returns. If the reading still jumps erratically after two cycles, check that the battery connector is fully seated.