I would highly recommend either speaking to "Chloride Exide" 

http://www.cekl.com/index.php?option=com_content&view=article&id=84&Itemid=27

or  Davis and Shirtliff  http://www.dayliff.com/index.php?option=com_content&view=article&id=263&Itemid=265

as they have highly specialized power backup system solutions (warranty+support included). There are a lot of other vendors that offer the same,but it all comes down to cost.  I am sure they will point you in the right direction of what you need. 

thanks 

Vince