MetroPCS LGMS840V Replacement Battery 3.7V 1500mAh

MetroPCS LGMS840V — 3.7V Li-ion 1500mAh Replacement Battery

This is a 3.7V lithium-ion cell rated at 1500mAh (5.55Wh) for the MetroPCS LGMS840V smartphone. It slots into the rear compartment and connects to the same charging and fuel gauge circuitry as the original. If your LGMS840V shuts down unexpectedly or no longer holds a charge, this cell replaces the degraded original.

• LGMS840V fit: The LGMS840V uses a fixed connector pinout that carries both charge current and fuel gauge data on the same flex contact. This cell matches that pinout, so the charging IC and the fuel gauge IC both initialise correctly on first boot.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on a LGMS840V-class board, confirmed BMS handshake, and verified the protection circuit trips at the correct over-voltage threshold before the cell ships.
• First-cycle fuel gauge reset: On first use after installation, disable fast charging and run one full discharge-to-charge cycle. The fuel gauge IC is calibrated against the discharge curve of the old cell. One slow cycle lets it recalibrate against this new cell before high-current charging begins.

Sudden shutdown at 20–30% on the replacement cell

This happens because the fuel gauge IC still references the voltage-to-capacity curve of the old, degraded cell. A fresh cell has a steeper voltage cliff near the bottom of its curve. The phone's software reads 25% but the actual cell voltage has already dropped below what the modem and display can sustain under load. Run one full discharge until automatic shutdown, then charge uninterrupted to 100% — after that cycle the gauge recalibrates and the premature shutoffs stop.

Phone warm near the battery compartment during first charges

A new cell arrives from storage at a higher internal impedance than a conditioned cell. The charging IC pushes current into that impedance, and the resistance converts some energy to heat during the first few cycles. This is normal and the warmth reduces as impedance drops across two or three full charge cycles. If the phone stays hot after three cycles, check that the rear cover is seated flat — a lifted cover traps heat against the cell.