Sorry to hear about your battery problem. I have not read the D4 manual yet about the battery but I assumed (always a mistake to assume but I like to live dangerously) it was like my D3x/s batteries. I have one battery in the cameras and one in the chargers. I try to run the batteries down before I put them back in the chargers and occasionally calibrate them so I get a true reading on their capacity. If I'm not mistaken the charger will deplete the battery all of the way down before it starts to charge when you calibrate the battery. I believe the D4 is exactly like the D3. When I got my D4 I ordered an extra battery and an extra Sony memory card because I am always around when things go wrong and I don't like to curse especially when it's my fault. Not to rub it in but as a NAPP member I get shipping from B&H free and if I order it before 4 PM I will have it the next day by 4 PM. It is great for satisfying my NAS problem. I hope you solve your battery problem without too much heartache or expense.