BV-L5C Nokia Lumia 640 LTE Replacement Battery 3.8V 2400mAh

Nokia Lumia 640 LTE / 640 Dual SIM — 3.8V Li-ion Replacement Battery (BV-L5C)

This is a 3.8V, 2400mAh Li-ion cell that replaces the original BV-L5C battery in the Nokia Lumia 640 LTE and Lumia 640 Dual SIM. It fits the standard battery bay with no modification. Install it when the original cell no longer holds a usable charge or causes unexpected shutdowns.

• Lumia 640 LTE and 640 Dual SIM compatibility: Both models use the same BV-L5C cell format — identical voltage rail at 3.8V, same physical footprint, and the same BMS handshake protocol. One replacement covers both variants without any adapter or firmware difference.
• Bench tested on actual hardware: We ran this cell through full charge and discharge cycles on a Lumia 640 LTE unit. The BMS accepted the cell without fault codes, charge current ramped correctly through CC/CV phases, and the protection circuit triggered cleanly at the low-voltage cutoff threshold.
• Fuel gauge recalibration on first use: After fitting this cell, disable fast charging and run one complete discharge-to-charge cycle at standard current. This lets the fuel gauge IC map the new cell's discharge curve before the coulomb counter locks in its reference points — skipping this step causes erratic percentage readings early on.

Sudden shutdown at 20–30% on the Lumia 640 after a cell swap

The Lumia 640's fuel gauge IC stores a learned discharge curve from the old cell. When a new cell goes in, that stored curve no longer matches the actual voltage profile of the replacement. Under load — LTE modem, screen at full brightness, or GPS active — the cell voltage drops faster than the IC expects, and the phone reads the voltage as critically low before the cell is actually empty. The fix is one full discharge-to-shutdown followed by a complete charge without interruption. After that cycle, the coulomb counter resets its reference and the percentage reading stabilises above 3.6V under load.

Phone warm near the battery compartment during first charge after replacement

A new cell arrives with higher internal impedance than a broken-in cell, which means the charge IC dissipates more energy as heat during the initial constant-current phase. This is most noticeable on the first one or two charge cycles and fades as the cell's impedance settles. It is not a fault — the charge IC on the Lumia 640 is within spec up to around 40°C at the case. If the back of the phone becomes uncomfortable to hold during that first charge, switch to a lower-output charger — a standard 5V/1A adapter keeps charge current well within the thermal headroom of the new cell.