BV-L5C Compatible Battery for Microsoft Lumia 640 LTE 3.8V 2400mAh

Microsoft Lumia 640 LTE — 3.8V Li-ion Replacement Battery (BV-L5C)

This is a 3.8V, 2400mAh Li-ion replacement cell for the Microsoft Lumia 640 LTE and Lumia 640 Dual SIM smartphones. It replaces OEM part number BV-L5C directly. Capacity is rated at 9.12Wh and dimensions are 93.50 × 37.30 × 5.20mm — confirming fitment before you open the phone is worth the 30 seconds.

• Lumia 640 LTE and 640 Dual SIM compatibility: Both models share the same battery bay geometry, connector pinout, and BMS communication protocol — the BV-L5C cell fits both variants without modification.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on a Lumia 640 LTE unit. The BMS handshake completed on first connection, charge IC accepted the cell without flagging an error, and voltage held steady through a full discharge curve.
• Fuel gauge recalibration on first use: After installing this cell, disable fast charging and run one full discharge-to-charge cycle before returning to normal use. The fuel gauge IC on the Lumia 640 is calibrated to the old cell's discharge curve — one complete cycle lets it map the new curve accurately and prevents erratic percentage readings early on.

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

This happens when the fuel gauge IC is still running the old cell's voltage-to-capacity curve. The replacement cell hits a voltage cliff — a sharp drop in cell voltage under modem or screen load — at a point the OS still reads as 20–30% remaining. The phone interprets that voltage drop as a critical low and cuts power. One full discharge cycle from 100% down to automatic shutdown, followed by a full charge, resets the coulomb counter and aligns the gauge to the new cell's actual curve.

Phone won't power on after the replacement battery sat in storage

Li-ion cells self-discharge during storage. If this cell dropped below 2.5V, the BMS will have entered lockout mode and will refuse to accept a charge current to protect the cell from damage. Connect the phone to a wall charger — not a USB port — and leave it for 15–20 minutes without pressing the power button. A wall charger delivers enough trickle current to nudge the cell voltage back above the BMS recovery threshold, typically around 2.8–3.0V, at which point the BMS re-initialises and normal charging resumes.