BV-4NW Nokia Lumia 928 Replacement Battery 3.8V 2000mAh

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

This is a 3.8V, 2000mAh Li-Polymer replacement cell for the Nokia Lumia 928 (RM-860, RM-5250). It slots into the same bay as the original BV-4NW and reconnects to the same charge IC and fuel gauge. Capacity figures are taken from the product specification, not estimated.

• Lumia 928 / RM-860 / RM-5250 compatibility: All three model numbers share the same physical bay, the same 3.8V charging rail, and the same BMS handshake points. One cell covers all three without modification.
• Bench tested on actual hardware: We cycled this cell on a Lumia 928 unit and monitored BMS communication across charge and discharge. The protection circuit held cutoff correctly at both ends and the charge IC accepted the cell without fault flags.
• Fuel gauge recalibration on first cycle: After installing this cell, disable fast charging and run one full discharge down to automatic shutdown, then charge uninterrupted to 100%. This gives the fuel gauge IC a clean reference discharge curve before it starts reporting percentage to the OS.

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

When the phone shuts off at 20–30% remaining, the fuel gauge IC is still reading the discharge curve from the old, degraded cell. The new cell's voltage drops faster under modem or display load than the IC expects, so the phone hits its cutoff voltage before the percentage reaches zero. This is a calibration issue, not a fault with the replacement cell. One full discharge-to-shutdown followed by an uninterrupted charge to 100% resets the coulomb counter and resolves the early cutoff.

Phone will not power on after the BV-4NW sat in storage

Li-Polymer cells in storage self-discharge slowly. If the cell drops below roughly 2.5V, the BMS enters a lockout state and the phone shows no response to the power button. Connect the phone to a wall charger — not a PC USB port — and leave it for 15–20 minutes without pressing anything. The charge IC trickle-charges the cell back above the BMS unlock threshold, after which normal charging resumes. If the charging indicator does not appear after 30 minutes on wall power, the cell has discharged below recoverable voltage.