The iPhone’s battery life continues to vex and confound, and for all our optimism in the cover feature on page 16, the chances of apple sacrificing screen fidelity or chassis slenderness to improve it are low.
So if you want your handset to last longer away from the mains, you’re probably on your own.
One option is this neat little battery unit by Just mobile, rendered in the firm’s trademark apple-imitating brushed aluminium. it’s about the size of a pack of cigarettes, if a little heavier (78 x 57 x 21mm, and 138g) and comes with a black bag with compartments to hold the battery and your iPhone. it’s a convenient and portable device, in other words.
The Gum Plus is rated at 5,200mah, which translates, according to the makers, into three full recharges for an iPhone. Just mobile also claims you can charge your iPhone from empty up to 90 percent in an hour, but our experience didn’t match this: our handset went from 4 to just 67 percent in that time.
An iPad will obviously get less satisfaction, but we gave it a shot anyway. a fully charged Gum Plus took our test iPad 3 from 27 to 56 percent before giving up the ghost; not bad as an emergency backup, but don’t depend on this as a tablet power source.
The Gum Plus has a Usb output port at one end and miniUsb input at the other for charging it up. you’ll need to supply your own Usb-wallplug adaptor if you want to charge it from the mains, but iPhone owners will have one lying around somewhere. and it is compatible with lightning devices, provided once again that you provide the relevant cable (Usb to lightning, in this case) yourself.
iPhone Portable Battery Charger
Source. iPad Phone User Issue 73