How old is the terminal? I am sure you could take it to a computer repair store and see if they are willing to pop it open and take a look, and run a battery test. They should be able to look at the port as well. But with the cost of labor and, truth be told, unsure if they can even replace the battery, it may simply be best to replace the whole terminal. If it is a recent purchase, then I would get with Square for warranty work.
