I've had some of mine refuse to take a full charge even when I know they're dead... I've brought em back with a verryyy slow charge, say 0.5A for a 5000, decharge, 1.5A, repeat... I haven't had one completely refuse a charge yet.
Tiger I - Panzer III - Panzer IV - Chi Nu Kai - Panther G - KV-1b 756(r)
M4A3(76) Sherman - T-34/85 - M3 Grant