slot 2 Smart Battery (Optimized to lengthen your iPhone performance time; No more out of power dilemma during important phone coversations) Solar panel can be constantly charged for the battery under sunshine. One hour of directly sunlight can charge the iPhone for 30 Mins talk time in 3G network and 60 Mins talk time in 2G network USB charging and SYNC without the need to disconnect your iPhone from the case (Mini USB cable included in package 4-LED indicators show you battery status. Each light means 25% power inside. ON/OFF Button for Optional Power Output Control/Bonus Dual USB Car Charger with 12 V outlet