Hi, I've recently bought refurbished Samsung Galaxy Tab 8.9 - SGH-I957, 16 GB. Tablet works fine, but baterry is draining prety fast. Worst is, that baterry goes down even in sleep mode. So every morning instead of using, I am charging I have no sim card inside,so I turned tablet to Airplane mode, turn on option "turn off wifi when screen turns off", I have tried reset tablet to factory default and still no progress with batery aprovement. Any ideas someone? Thank you