BL-41ZH Replacement Battery for LG Optimus C40 3.8V 1900mAh

LG Optimus L50 / Leon Series — 3.8V Li-ion Replacement Battery (BL-41ZH)

This is a 3.8V, 1900mAh Li-ion replacement battery for the LG Optimus C40, Optimus L50, Leon, and Leon 4G smartphones. It uses OEM part numbers BL-41ZH, BL-41ZHB, EAC62378407, and EAC62778201. Swap it in when the original cell can no longer carry the phone through a normal day of calls, messages, and apps.

• Leon and Optimus series compatibility: These models share the same removable battery bay, connector pinout, and BMS handshake protocol — all pulling from a common 3.8V cell platform. One part number covers the full range without modification.
• Bench tested on actual hardware: We cycled this cell on an Optimus L50 and monitored BMS cutoff behaviour through full charge and discharge. The protection circuit triggered correctly at low-voltage threshold, and charge acceptance was stable across three consecutive cycles.
• Fuel gauge recalibration on first use: On first use after installation, disable fast charging and run one full discharge-to-charge cycle. This gives the fuel gauge IC time to map the new cell's discharge curve before high-current charging begins on an uncalibrated cell.

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

This happens because the fuel gauge IC is still reading the discharge curve of the old, degraded cell. The new cell has a steeper voltage drop under modem and screen load near the bottom of its range. The phone's power management firmware sees the voltage collapse and triggers an emergency shutdown before the displayed percentage reaches zero. One complete discharge cycle — draining to auto-off, then charging to 100% uninterrupted — resets the coulomb counter reference and corrects the premature cutoff.

Phone feels warm near the battery during the first charge after replacement

A new cell has higher internal impedance than a broken-in one. The charge IC compensates by pushing slightly more voltage during the constant-current phase, which generates more heat than you'd see on a cycle-worn cell. This is normal for the first one or two charges and settles as the cell's impedance drops with use. If the phone stays warm beyond the second full charge cycle, check that the battery contacts are fully seated and no debris is trapped in the bay.