I have a new Tab 3 that has sat in its box for a couple of years unused. I tried to charge it today and boot it up without success. When I hold the power button to power up, it sits on the Samsung Tab 3 screen. I have tried to clear the data/factory reset without success (holding power/vol up/home buttons). If I power it down and plug in the charger cable, I get the battery symbol but it doesn't show any green segments, even if left on for an hour. If I unplug the charger, the battery symbol remains (until I power it off)! In frustration, I took the back off and disconnected and reconnected the battery - no change. With the charger disconnected, I measure across the battery and I'm getting 4.3V, which suggests that the battery is OK.
Anyone have any other suggestions that I can try? I'm using the (new) factory charger and microUSB cable (and I've tried alternatives). I've ordered a USB energy meter, which arrives at the weekend, to see if the device is drawing any current from the charger.