About this replacement
Nokia Lumia 810 / 822 — 3.7V Li-ion Replacement Battery (BP-4W)
This is a 3.7V, 1400mAh (5.18Wh) Li-ion battery using OEM part number BP-4W. It fits the Nokia Lumia 810 and Lumia 822 Windows Phone smartphones. Buy this when the original cell no longer holds enough charge for daily use.
- Lumia 810 and 822 compatibility: Both models run the same 3.7V battery rail, use an identical physical connector, and communicate with the same fuel gauge IC. BP-4W is the correct part for either handset — the BMS handshake is the same across both.
- Bench tested on actual hardware: We cycled this cell through full discharge and charge on the Lumia platform. The BMS accepted the cell without fault flags, charge current tapered correctly at end-of-charge, and the fuel gauge IC registered the new cell without intervention.
- Fuel gauge recalibration on first use: After fitting this cell, disable fast charging and run one complete discharge-to-charge cycle before normal use. The fuel gauge IC was calibrated to your original cell's discharge curve — one full cycle against the new cell lets it rebuild an accurate state-of-charge map.
Why the Lumia 810 reports wrong battery percentage after a cell swap
The Lumia 810 uses a coulomb-counter-based fuel gauge IC that tracks charge in and out of the original cell over its lifetime. When you swap the cell, the IC still holds the old discharge curve in memory. It will report a percentage based on a curve that no longer matches the new cell's chemistry. The fix is one full discharge — down to automatic shutdown — followed by a full uninterrupted charge. After that single cycle, the IC recalibrates against the new cell and percentage reporting stabilises.
Sudden shutdown at 20–30% on the replacement cell
This happens when the cell voltage drops sharply under modem or display load — a voltage cliff the fuel gauge IC did not predict. The OS reads 25% state-of-charge, but actual cell voltage collapses below the 3.0V cutoff the moment current demand spikes. It is not a faulty battery — it is a miscalibrated gauge reading an uncycled cell. Run one full discharge to shutdown, then charge uninterrupted to 100%. After that cycle, the gauge maps the actual voltage cliff and shutdown warnings will fire at the correct percentage.