Why my camera show's battery empty icon?

Can anyone help me plzz? My 70D camera… almost 6+ month i didn’t use this… but now when i turn it on the Battery icon show full..but after 2/3 minutes or 2/3 shots it shows empty Battery icon and going to turn off…. If i Again turn off/on the switch…its show Again full.. And same behave….. But when i connect to charger its show full charge within few minute.. So..what can i do now?