You can find this information printed on the back of your keyboard.
ARyee 7800mAh 11.1V E6400 Battery Laptop Battery for Dell Latitude E6400 E6500 E6410 E6510，Dell Precision M2400 M4400 M4500
DBTLAP CMOS RTC Battery Compatible for Dell Latitude E6400 E6500 E4310 CMOS BIOS RTC Battery
DBTLAP CMOS RTC Battery For DELL Latitude E6400 E6500 E6410 E6510 BIOS BACKUP RESERVE
Dell Latitude E6400 E6500 Precisionn M2400 Microphone Board - 0XP558 XP558
English British Keyboard Dell Latitude E6400 E6500 NSK-DB10U 0HT517 507
vhbw BIOS Battery compatible with Dell Latitude E6400, E6410, E6500, E6510, E5400, E4300 Computer Notebook (200 mAh, 3 V, Li-Ion)
