About this replacement
OnePlus Nord / AC2003 — 3.87V Li-Polymer Replacement Battery (BLP785)
This is a 3950mAh (15.29Wh) Li-Polymer cell for the OnePlus Nord (AC2003). It replaces OEM part BLP785 when the original cell has degraded, swells, or no longer holds a charge. Voltage is 3.87V nominal — matched to the Nord's power management IC.
- Nord / AC2003 fit: Both model variants share the same battery bay dimensions, connector pinout, and BMS handshake protocol. The BLP785 footprint is 83.38 × 62.40 × 4.30mm — physical fit and the NTC thermistor line are confirmed compatible across both SKUs.
- Bench tested on actual hardware: We cycled this cell on a Nord unit and monitored BMS communication across charge and discharge. The protection circuit responded correctly to trickle charge entry, full-charge cutoff, and load-spike conditions without tripping into fault state.
- First-cycle calibration tip: After fitting this cell, disable Warp Charge for the first full discharge-charge cycle. This lets the fuel gauge IC build an accurate coulomb counter baseline against the new cell's discharge curve before high-current charging pushes current into an uncalibrated state.
Why the Nord reports wrong battery percentage after a cell swap
The Nord uses a coulomb counter that tracks charge in and out of the original cell over its lifetime. When you fit a new cell, that counter still holds calibration data mapped to the old cell's degraded capacity curve. The mismatch means the fuel gauge IC reports percentages that don't reflect what's actually in the new cell. One complete slow charge-discharge cycle resets the learned curve and brings the percentage readout back in line.
Sudden shutdown at 20–30% on the replacement cell
This happens when the fuel gauge IC hasn't recalibrated yet and the displayed percentage is ahead of the cell's real state of charge. Under modem or display load, voltage drops sharply near the actual depletion point — the BMS cuts power before the OS can warn you. It's not a faulty cell. Run one full discharge down to automatic shutdown, then charge uninterrupted to 100% to anchor the fuel gauge to the new cell's voltage-capacity curve.