Amazon.com: GHU Premium 58Wh Battery for Dell E6400, E6500, E6510, M4400: UL Tested, Over 500 Recharge Cycles, Fast Charging, Long-Lasting Over 3 Hours - Compatible with Dell Latitude E6500, E6510, M4400 Battery :
Replacement BATTERY For Dell Latitude E6400 E6410 E6500 E6510 PT434 W1193 KY477 - Walmart.com
Xtend Brand Replacement For Dell Latitude E6400 E6500 and Precision M2400 M4400 M6400 Battery - Newegg.com
Dell Latitude E6400 Battery Replacement - iFixit Repair Guide
Dell Latitude E6400 E6500 Laptop Battery KY265
Dell Latitude E6400 Battery Replacement - iFixit Repair Guide