About this replacement
Dell Inspiron 14-5490 / 15PR Series — 11.4V Li-Polymer Replacement Battery (266J9)
This is an 11.4V, 4150mAh (47.31Wh) lithium-polymer battery for the Dell Inspiron 14-5490, 15PR, and related Inspiron notebook models. It replaces OEM part numbers 266J9 and M4GWP. The cell slots into the original bay and connects to the same BMS handshake the Dell EC expects on power-on.
- Inspiron 5490 and 15PR platform fit: These Inspiron models share a common 11.4V three-cell Li-Polymer architecture, the same physical connector pinout, and the same EC communication protocol — which is why one cell covers both the 14-inch and 15-inch chassis variants in this generation.
- Bench tested on actual hardware: We ran this cell on a 5490 unit and confirmed the BMS completed a full charge cycle without tripping an overcurrent fault. The EC recognised the cell, reported charge state correctly, and the protection circuit cut in cleanly at the low-voltage threshold during discharge.
- Dell EC learn cycle after install: After fitting this cell, run the laptop down to hibernate cutoff, then charge uninterrupted to 100%. This completes the Dell battery learn cycle, resets the BIOS health register, and clears the inaccurate "consider replacing your battery" warning that appears after any cell swap.
Why the Inspiron 5490 shuts down at 20–30% remaining after a battery swap
The Dell EC tracks charge state using fuel gauge data stored during previous discharge cycles on the old cell. When a new cell goes in, that stored data no longer matches actual cell chemistry, so the EC miscalculates the voltage cliff. Under full CPU and display load, the new cell hits a voltage dip the EC reads as empty before the cell actually is. Running two to three full discharge-to-hibernate cycles recalibrates the fuel gauge IC against the new cell's actual discharge curve and pushes the phantom shutoff point back down toward 5–8%.
BIOS shows "poor battery health" immediately after installing a new cell
The Dell BIOS reads health status from an EEPROM register that the old cell wrote during its degraded final cycles. A fresh cell does not automatically overwrite that register on first boot. The fix is to run the Dell battery learn cycle: discharge fully to hibernate, then charge to 100% without interruption. After that cycle completes, the EEPROM health register updates to reflect the new cell's actual state, and the BIOS health warning clears. If it does not clear after one cycle, run a second full cycle before assuming a fault.