Major issue with purchasing batteries this old,  most if not all web sources are either "pulls" or the batteries have been sitting on a shelf for years. Best hope is to order from Dell directly or get in touch with one of the battery pack rebuilders. 
Hello, does anyone have a reliable vendor for a Dell Perc 4/e battery. I believe it's a LSI megaraid controller.  I think the part number is: BAT-NIMH-3.6-01 Below is what it looks like[IMAGE]
Dell Perc 4/e/LSI Battery Vendors