If you take the battery back to where you bought it, they can test it to see if it is good or bad.
Another possibility is that one of you battery cables is bad. I have see them where they look good on the outside but they will be corroded on the inside part where the cable goes into the terminal clamp.
Another possibility is that one of you battery cables is bad. I have see them where they look good on the outside but they will be corroded on the inside part where the cable goes into the terminal clamp.