Stop testing it and replace it. If you get 4 years out of a battery you've beaten it into the ground. you've already got 5 years. It needs to be replaced and unless they are using some extra scientific specialty battery testing procedures (it took batteries plus 1 day after i dropped off my battery with them to figure out my problem cause it always tested ok and thats all they do is work on batteries) they won't know. Just get a new one. You'll see.
Just the fact that you put a charger on it and it started tells you it doesn't work.