Hello tdubb123,
Here is a link that shows you how to open the controller. You will need to look on page 222 & it walks you through how to remove the battery. ftp://ftp.dell.com/Manuals/all-products/esuprt_ser_stor_net/esuprt_powervault/powervault-md3200i_Owner%27s%20Manual_en-us.pdf
Please let us know if you have any other questions.