BV-4NW Microsoft Lumia 928 Compatible Battery 3.8V 2000mAh

Microsoft Lumia 928 / RM-860 — 3.8V Li-Polymer Replacement Battery (BV-4NW)

This is a 3.8V 2000mAh Li-Polymer cell replacing the OEM BV-4NW battery in the Microsoft Lumia 928 (RM-860, RM-5250). It fits the internal slot without modification and connects to the existing charge IC and fuel gauge circuit. Capacity matches the factory specification at 7.6Wh.

• Lumia 928 / RM-860 / RM-5250 platform fit: All three model numbers share the same chassis, connector pinout, and BMS handshake. The BV-4NW cell interfaces directly with the Lumia 928's fuel gauge IC, so no adapter or firmware workaround is needed.
• Bench tested on actual hardware: We cycled this cell through the Lumia 928's charge IC and confirmed the BMS accepted charging without error, held voltage above 3.6V under display and modem load, and released cleanly at the low-voltage cutoff.
• Fuel gauge recalibration on first cycle: After installing this cell, run one full discharge to automatic shutdown, then charge uninterrupted to 100% before normal use. The Lumia 928's coulomb counter resets its learned curve against the new cell during that first complete cycle — skipping this step causes erratic percentage readings for days.

Sudden shutdown at 20–30% on the Lumia 928 after a cell swap

The Lumia 928 pulls hard when the modem is active on LTE or when the screen brightness peaks. A new cell with an uncalibrated fuel gauge IC can report 25% remaining while the actual open-circuit voltage has already dropped below the modem's minimum operating threshold. The phone cuts power to protect the SoC before the OS registers low battery. One full discharge-to-shutdown cycle lets the coulomb counter map the new cell's actual voltage curve, after which the percentage tracks accurately and the early shutdowns stop.

Phone won't power on after sitting in storage with a flat BV-4NW

Li-Polymer cells that discharge below approximately 2.5V trigger a BMS lockout to prevent thermal runaway during recovery charging. If the Lumia 928 sat unused for months with the old or new cell fully drained, the BMS will block normal charge input and the phone appears completely dead. Connect it to a wall charger — not a PC USB port — and leave it for 20–30 minutes without pressing the power button. The charge IC delivers a low-current trickle to recover the cell voltage above the 2.8V threshold, after which normal charging and boot resume automatically.