Most batteries are sealed now so you don't need to be adding water to batteries anymore. And that isn't always a fix for batteries. There could be a bad cell that could be causing the battery to not take a good charge. Bad connections are another problem. Just remember, You have to do a full charge on the battery before they can do a load test. If it won't take a charge, then you know for sure that there is a problem with the battery. But if it does, there still could be internal problems that either won't allow it to charge, or won't allow it to have it's full amp draw. Like bad cells or broken internal plates. Oh, and if the battery is about 5-6 years old, ot won't hurt to start looking for a new battery.
Good luck.