as soon as I unplug brand new fully charged 15 g e 5 itlooses batery charrapidly, even tough it is in sleep mode

brand new phone just activated and transferred 179 contacts, nothing else has been added. Soon after it says "100% charged", I unplug it and push the button on top if device to (?) save power I imagined... There after -phone incurrs no activity what so ever... within 2 hours the battery has lost at least 50% of its charge. EVERY time... phone not perpetually connected to juice?, seems not feasible.t I do not think this is acceptable loss, or is it a glitch in the new line i phone 5? What a mistake this appears to be ... any one experienced similar?