I came across a couple of old phones that I put away in a cupboard a few years ago. They were working fine when they were last in use, and one of them, 7 years old has charged up fine, but the other one will now not charge up at all. I understand that a battery will discharge after a period of non use but can it 'die' altogether? Even the spare battery which was new when it was put away is the same. (they are Ni-MH type) I'ts definately not the charger as it's been tested on another phone. Any ideas how to revive them?