About this replacement
LG Prada 3.0 / P940 / SU880 — 3.7V Li-ion Replacement Battery (BL-44JR)
This is a 3.7V, 1700mAh Li-ion cell built to replace the OEM BL-44JR battery in the LG Prada 3.0, P940, K2, and SU880 smartphones. The BL-44JR sits in a narrow shared platform across these LG models — same connector, same BMS handshake protocol, same physical footprint at 65.20 × 44.00 × 4.70mm. When the original cell degrades, voltage sag under screen and modem load becomes the first failure sign.
- Prada 3.0 / P940 platform fit: These models share a common power rail at 3.7V nominal and use the same BMS communication line to the charge IC. The BL-44JR connector locks to the same board header across all listed variants, so no adapter or modification is needed.
- Bench tested on actual hardware: We ran charge cycles on this cell against the P940 charge IC and confirmed the BMS negotiation completes correctly — the device registers the battery, accepts charge current, and reports state-of-charge without error flags on the first full cycle.
- Fuel gauge recalibration on first use: After installing a new cell, disable fast charging and run one full discharge-to-charge cycle before normal use. The fuel gauge IC on the P940 is calibrated to the old cell's discharge curve — one complete cycle lets it remap against the new cell before high-current charging begins.
Why the P940 reports the wrong battery percentage after a cell swap
The P940 uses a coulomb counter inside the fuel gauge IC that tracks charge based on the previous cell's internal resistance and discharge profile. A new BL-44JR cell has different impedance characteristics, so the IC's stored model no longer matches what it's measuring. This mismatch shows up as percentage jumps, early "low battery" warnings, or a reading that stalls at one value for extended periods. One full discharge cycle — down to auto-shutdown, then a full charge — forces the IC to relearn the new cell's curve.
Sudden shutdown at 20–30% on the replacement cell
This happens when the fuel gauge IC hasn't recalibrated yet and the cell hits a voltage cliff under simultaneous modem and display load. The P940's processor draws a short current spike that the uncalibrated cell can't sustain, dropping cell voltage below the BMS cutoff threshold even though the displayed percentage reads mid-range. The phone shuts down as a protection event, not a true dead cell. Run one full discharge-to-shutdown cycle, recharge to 100%, and the cutoff voltage should align with the updated fuel gauge model — typically resolving shutdowns above 3.4V per cell.