2000 C5 won't start just hearing relay's clicking
 

I am having some technical issues I think but not sure where to look. This past Monday it was pouring down rain and I drove about 5 miles to the store and back for gas. Didn't drive through any high water anywhere but I went out to start my car and it was like the battery is dead or low but when I turn the key off I heard relay's clicking. I checked and #37 (monitor ld) and another one across on the other side I think 42 but same type repay in fuse panel in passenger floor board. So I was able to jump start it from another vehicle after running it to help charge the c5 battery and it was real sluggish and sounded like it wasn't gonnna start but finally did. So I drove it around to charge battery was charging at 13.5 or so on gauge and then when I got back I turned it off and checked it to see and it wouldn't start doing the same thing. So I've been charging the battery for a day but still does same thing and battery reads 12 volts with my meter. Any suggestions would be greatly appreciated. And I checked and all the lights even hood light are shutting off.
Thanks

How old is your battery? I would have the battery load-tested to see if it is still good. A battery with one or more bad cells will not charge sufficiently.

Dave

Need help problem with clicking from fuse panel and lights
 

Having similar problems did you find out what your problem was?

I recently had the same experience with my C5 coupe. I took the battery to have it load-tested and the results showed that the battery was bad (would not accept full charge). I replaced it with a $63 Costco Kirkland battery and all is good.