About this replacement
Dell Latitude E5400 / E5500 / E5410 / E5510 — 11.1V Li-ion Replacement Battery (KM668)
This is an 11.1V, 4400mAh (48.84Wh) Li-ion battery for the Dell Latitude E5400, E5500, E5410, and E5510 notebooks. It uses the same connector and BMS handshake as the OEM cell, so the laptop recognises it without driver changes. OEM part numbers covered include KM668, KM742, MT186, RM649, PW640, WU841, and over 30 additional Dell cross-references.
- E5400 / E5500 / E5410 / E5510 compatibility: These four Latitude models share the same battery bay dimensions, 11.1V power rail, and SMBus handshake protocol — one cell covers all four without any adapter or firmware patch.
- Bench tested on actual hardware: We ran this cell in a Latitude E5400 and E5510. The BMS negotiated correctly with both BIOS versions, charge current stepped down at the expected threshold, and the fuel gauge IC accepted the new cell's EEPROM data without a fault flag.
- Post-install calibration on Dell Latitude: After fitting, run the laptop on battery until it hits hibernate cutoff, then charge uninterrupted to 100%. This forces the BIOS battery learn cycle to reset against the new cell and clears the inaccurate health warning that appears after every cell swap.
BIOS reporting battery health as poor immediately after replacement
Dell's BIOS stores battery health metrics tied to the original cell's EEPROM data. When a new cell is installed, the old data still sits in memory, so the health indicator reads against it and flags a warning. This is not a fault with the replacement cell. Run one full discharge-to-hibernate cycle followed by an uninterrupted charge to 100% — this triggers the battery learn cycle and overwrites the stale EEPROM reference values.
Laptop shuts down at 20–30% charge shown on screen
The fuel gauge IC calibrates its empty-point estimate against the old cell's discharge curve. A new cell has a different voltage cliff — the point where cell voltage drops sharply under full CPU and display load — so the gauge triggers shutdown well before the actual 0% threshold. The fix is two to three full discharge-and-charge cycles, which lets the fuel gauge IC map the new cell's actual voltage curve. After calibration, shutdown should align with the gauge reading below 5%.