Charging system on a 1999 Exterra

At least I think its a 1999. Its my son-in-laws Extrra and he is in the Marines and stationed in Virginia Beach, but im in Florida, so I cant help do much with it.

Shortly before had to go away for over a month on some training, the Exterra wouldnt start. I dont know if they could jump it off or not, but I had him charge the battery a little, then it would start. He took the cable off of the battery and it died. While the battery was charged, it seemed to want to start ok. He was told it might have gotten some water in something and let it dry out while he was gone.

Now that he is back, he says the battery wont even take a charge and yes, he took it out of the truck.

Im old school and used to voltage regulators that can stick, but I guess the newer ones dont have such a thing?

Im tempted to buy him a new battery and have him go to Autozone to see if they can tell him something. or any other suggestions ?

Thanks,
David

I would get a new battery. The water they were talking about is the distilled water in the battery if that ends up empty the battery will not charge our hold a charge.

It has to be a 2000 or newer nos. didn't not make xterra's till 2000.