Whoever said that power corrupts obviously didn’t own a smartphone. Absolute power is an absolute necessity, all the more so with the big screen, fast processor and multitasking capability of the S4. All of the fun and games you’ll be having with the phone will make you an angry bird (lol) if you run out of juice.
For that reason, I highly recommend getting a power bank – essentially, an external battery in a sealed case. Powerbanks come with a USB cable; you connect it to a power source such as a laptop to charge the powerbank. Some charge instead via flip out blades for plugging into the wall. In either case, you carry the charged up powerbank – and the cable – in your pocket, purse, backpack, briefcase or whatever and use it to charge the phone (using the same USB cable) when you see the battery meter sinking into the sunset.
Powerbanks are rated in mAh (milliamp hours), just like the battery in your cellphone. They have about 70% to 80% efficiency; the rest of the energy is lost to heat. This means, for instance, that a 4400 mAh power bank wouldn’t completely fill your S4’s 3600 mAh battery. Even a 4000 mAh unit would fall a bit short (do the multiplications – even 0.80 x 4000 is less than 3600). On the other hand, you’ll probably hook up the powerbank before your battery is completely dead.
All units reviewed here include 1 Amp ports for use with smartphones. In addition, the units reviewed that are 5600 mAh and up also include 2.1 A or 2.5 A outputs that can be used with smartphones or tablets.
Powerbanks – which some companies call simply external batteries; there’s no standard terminology – have become largely commodified, but not the truly small or large ones. Advertised as the smallest is the Powerocks Tarot, a 1500 mAh baby clad in sleek aluminum that will give your S4’s 3600 mAh battery a charge to about 1/3 full if you start from fully discharged. The unit is the height and width of a credit card and about as thick as eight of them. It looks great and slips easily into a pocket.
Another small unit is the Anker Astro Mini, a 3000 mAh unit available in black or silver. This one is a small cylinder, like an oversize lipstick or a small flashlight. (Guys, don’t have a panic – the look is very unisex.)