i am very happy with the external battery charger. once fully chared, i was able to charg an iPad2 from 20% to full and an Kindle from 15% to full before it nedded re-charge. Charging iPhone did not use much power at all so i am sure it can charge iPhone many times before needing a re-charge. It is nice and compact and a great companion on the road as i travel a lot. i will recommend it.