I've had my Samsung Galaxy s 3 for 5 months and I've had a couple instances in the last month where right after taking it off the charger and using it for less than 5 minutes the battery percentage would drop from 100% to 50% or less. And last night when I put it on the charger, completely dead, it did not start to charge. It stayed at 0% for at least an hour. I switched it into airplane mode in hopes to charge faster with no luck. Finally I turned the device off completely and it slowly charged to 28% overnight and was still not fully charged in the morning. Do I just need a new battery or a new phone?