I have bought several cheaper portable chargers none of which has really worked with my iPhone 4. This device works brilliantly certainly charging iphone 4+ times from flat. No iPhone errors "This device is not supported" or disabled by iPhone. One of the keys is the 5000mAh capacity high tech battery. Most other devices are at most 1900mAh using very cheap cells. A useful other aspect is that it turns itself off when not in use. Which is particularly useful if other people borrow it and forget to turn it off after use. Having all the various adaptors supplied with it is a bonus as the whole family or friends can benefit from it as well. Build quality superb and a nice touch having the travel padded sock. A must have accessory for the gadget enthusiast.