I bought a spare when I bought the camera (I'm the type who usually prefers spares to my spares).
I have had zero problems. I shot over 1700 images at a soccer game on Sunday and only had one bar missing on the icon of the first battery (did not look at the percentage).
I hate to suggest spending money to someone already upset, but I would get a second battery, see what happens. You may have an OK battery and a bad charger; you may have a problem with the camera. Or it may just be a defective battery, and you will then have replaced it.
If you find for sure it is the battery, you can start off with "I bought another to compare and.... " and at least show you have eliminated usage or other problems.
When you take it off the charger and look in the menu display does it say 100%?