About this replacement
Dell Latitude E6400 / E6500 — 11.1V Li-ion Replacement Battery (PT434)
This is an 11.1V, 6600mAh (73.26Wh) Li-ion battery for the Dell Latitude E6400, E6500, Precision M2400, and Precision M4400 series laptops. It replaces a wide range of OEM part numbers including PT434, KY477, FU268, C719R, and TX283. Install it when the original cell can no longer hold charge through a standard work session unplugged from mains.
- E6400 / E6500 / M2400 / M4400 compatibility: These four platforms share the same 11.1V battery bay, connector pinout, and SMBus communication protocol — one cell fits all without modification or adapter.
- Bench tested on actual hardware: We ran this cell on an E6400 through full charge and discharge cycles. The BMS held communication across the SMBus, charge termination triggered cleanly at 100%, and the pack reported correct voltage at each state-of-charge step.
- First-cycle calibration after install: After fitting this battery, let the laptop discharge fully to hibernate cutoff, then charge uninterrupted to 100%. This resets the BIOS battery learn cycle and clears the inaccurate health warning that appears after every cell swap on Dell Latitude hardware.
BIOS reporting battery health as poor immediately after installation
Dell's BIOS reads health data from the EEPROM embedded in the battery pack, not from live cell measurements. A new replacement cell carries EEPROM values that don't yet match the laptop's learned charge history, so the BIOS flags it as degraded on first boot. Running one complete discharge-to-hibernate then a full uninterrupted charge gives the firmware enough data to recalibrate. After two to three full cycles, the health indicator typically returns to normal without any firmware update or BIOS change.
Laptop shutting down at 20–30% charge shown on screen
This happens when the fuel gauge IC still holds calibration data from the old, degraded cell. The percentage shown is calculated against the old cell's curve, so the new cell hits its actual voltage floor well before the gauge reads zero. The fix is a full discharge to hibernate cutoff — not a forced shutdown — followed by a complete charge to 100%. After two to three of these cycles the fuel gauge IC recalibrates against the new cell's actual capacity curve and shutdowns stop occurring above 10%.