Question : APC Smart-up 1500 XLM

I have a APC Smart-up 1500 XLM, the other day (4 days ago) the power went up and the backup battery just did not work. It was purchase over 4 years ago 04-2006. I've tried logging into the interface to see if there is an area that will tell me if I need to replace the battiries but no such luck. It does state that the system passes, see below:
Self-Test Result:  Passed
 Self-Test Date:  07/05/2010
 Calibration Result:  Unknown
 Calibration Date:  Unknown

Question how can I tell if I should replace battiery? I unplugged it this morning and again the devices I have on it two 3COM 48 port switches just shutdown. Any suggestions?
 

Answer : APC Smart-up 1500 XLM

Try this post from APC support.

http://nam-en.apc.com/cgi-bin/nam_en.cfg/php/enduser/std_adp.php?p_faqid=3078&p_created=1071173245&p_sid=WdnQwe4k&p_accessibility=0&p_redirect=&p_lva=&p_sp=cF9zcmNoPTEmcF9zb3J0X2J5PSZwX2dyaWRzb3J0PSZwX3Jvd19jbnQ9OTE4LDkxOCZwX3Byb2RzPTAmcF9jYXRzPSZwX3B2PSZwX2N2PSZwX3NlYXJjaF90eXBlPWFuc3dlcnMuc2VhcmNoX25sJnBfcGFnZT0xJnBfc2VhcmNoX3RleHQ9QVBDIFNtYXJ0LVVQUyBYTCBNb2R1bGFyIDE1MDBWQQ**&p_li=&p_topview=1