This a really good portable battery/charger it is fairly compact, well made and will charge up my completely dead smartphone battery about 3 times. It has smart charging circuits in it which means that it will detect the maximum voltage that the device should be charged at and automatically adjust the charge its sending out to that amount. It charges my devices pretty quickly and its compact size means it doesn't take up tons of room in my purse. I definitely recommend this portable charger. #RankBoosterReview