Nokia Lumia 1520 Replacement Battery BV-4BW 3.8V 3500mAh

Nokia Lumia 1520 / 1520.3 — 3.8V Li-Polymer Replacement Battery (BV-4BW)

This is a 3.8V, 3500mAh Li-Polymer cell built to the BV-4BW specification for the Nokia Lumia 1520, Lumia 1520 3G, and Lumia 1520.3. It fits the same connector footprint and matches the BMS handshake the phone's charge IC expects. Capacity is rated at 13.3Wh.

• Lumia 1520 series compatibility: The 1520, 1520 3G, and 1520.3 all share the same battery bay geometry, connector pinout, and BMS communication protocol — that is why one cell covers the full line. Voltage rail and thermistor pin position are identical across these variants.
• Bench tested on actual hardware: We cycled this cell in a Lumia 1520 unit and confirmed the BMS handshake completed without fault codes. The charge IC accepted the cell and stepped through trickle, constant-current, and constant-voltage phases correctly.
• Fuel gauge recalibration on first use: After installation, disable fast charging and run one full discharge-to-charge cycle before normal use. This lets the phone's fuel gauge IC map the new cell's discharge curve before high-current charging begins pushing current into an uncalibrated cell.

Sudden shutdown at 20–30% on the Lumia 1520 after a cell swap

The Lumia 1520's fuel gauge IC retains the discharge curve of the old cell in its coulomb counter. When a new cell is installed, the IC applies the old curve to the new cell's actual voltage profile. At around 20–30% reported charge, the new cell's real terminal voltage drops below what the modem or display can sustain under load — the phone cuts out even though the gauge says charge remains. One complete discharge cycle below 5% and a full charge to 100% forces the IC to relearn the curve. After that cycle, reported percentage and actual charge track correctly.

USB fast charge not working after replacing the BV-4BW cell

On the first cycle after installation, the Lumia 1520's charge controller may reject the fast-charge handshake if the new cell's BMS reports an unrecognised state-of-charge signature. The phone falls back to standard 5V charging as a safety measure. Run one standard-rate charge from near-empty to full — this allows the BMS to sync its internal state with the phone's charge IC. Fast charge typically resumes from the second cycle onward once both sides agree on the cell's parameters.