goBAT II review
There are plenty of portable battery packs for iPhones and iPads. Some battery packs are built into iPhone cases, which is handy, but means that you're stuck with a bulky case. Scosche's goBAT II is actually a bigger than an iPhone 4, and weighs only slightly less (164g compared to 174g), but it's not going to weigh you down if you need a power boost.
Scosche promises that an iPhone 4 will get 2.6 charges out of the battery pack. We tested it and we did indeed manage that many charges, and crucially we left a whole week between charges two and three, proving that the battery pack maintained its power at least for that amount of time.
A fully charged goBAT II can charge an iPad to just over half full. Of course, Apple claims a fully charged iPad can give you 10 hours of power, so 55 per cent is going to give you a fair bit of use. You can tell how much charge is left in the battery pack by pressing the button, four lights indicate fully charged; by the time you are down to one or two lights you won't manage a whole charge, but you'll get something out of it.
One important point. The goBAT II has two USB ports, this can be used to charge two devices at once. The 2.1A USB port is for an iPad, and the 1A port is for an iPhone or iPod. However, Scosche warns that overload circuit protection will shut off the battery pack if the consumption exceeds 3A. This means that the battery pack will not charge an iPad and iPhone at the same time if both devices are fully drained.
While it's quite bulky compared to some solutions, the goBAT II has a number of points in its favour: it lets you charge two items at once; it will completely charge an iPhone 4 more than twice; and it keeps its charge between uses.