A battery case is a handy tool to keep your phone running all day, but in doing so, it adds considerable bulk to your device. The stylish Flux Battery Case ($74.99) is an exception. It's the thinnest, lightest iPhone 7 case we've tested, and features an innovative design with a detachable Lightning connector. At 1,500mAh, it doesn't provide as much extra battery life as larger cases like the ZeroLemon Slim Juicer, our Editors' Choice, but it also weighs less than half as much. If you like to travel light, the Flux is a solid alternative.
Design and Features
The Flux is made out of plastic and comes in non-branded gold, gray, matte black, rose, and silver, making for a refreshing change from most of the all-black polycarbonate slabs out there. It's also much thinner and lighter than the competition, measuring in at 5.5 by 2.7 by 0.4 inches (HWD) and 2.0 ounces. The Slim Juicer is a hefty 6.0 by 2.8 by 0.6 inches and 5.3 ounces, and even the Mophie Juice Pack Air seems a bit big in comparison at 5.9 by 2.8 by 0.7 inches and 3.5 ounces
It's relatively easy to snap your iPhone into the one-piece case, though taking it out is a bit more of a chore. But since the case leaves your Lightning port accessible, there is little reason you'll have to take your phone in and out.
In terms of protection, the Flux isn't the most durable case we've seen. There's no raised edge along the sides to keep the screen from making contact with the ground in case you drop it. Both the Juice Pack Air and the Slim Juicer offer a bit more protection, but do so at the cost of a bulkier form factor.
Along the sides the case are cutouts for access to all the iPhone's ports and buttons. The most interesting physical feature is located at the bottom right. It's a small rectangular protrusion with a battery symbol on it. Pull it out, and you'll see it's actually a small Lightning connector (about the size of a USB dongle) alongside four charging contacts. When you pull it out and plug it into your phone's Lightning port, the charging contacts align with the case and provide power to your phone.
It's a unique design that makes it easy to use you phone with wired headphones without having to take the Flux off, a feature most other cases lack. That said, the Lightning connector is rather small, so you'll want to keep it slotted in the case when you're not using it so you don't lose it. Thankfully, you get two in the package.
The case itself can be charged with your iPhone's Lightning cable through the port that's revealed when you pull out the Lightning connector. The Flux supports pass-through charging.
Battery status can be checked on the back through three small LEDS toward the bottom. To check your how much power is left, just press in the charging contacts on the bottom of the case with your finger.
Performance and Conclusions
The Flux's 1,500mAh cell gave our depleted iPhone 7 an additional 2 hours, 14 minutes of battery life while streaming full-screen video over LTE. That's a lot less runtime than both the 2,525mAh Juice Pack Air (3 hours, 49 minutes) and the 4,000mAh ZeroLemon Slim Juicer (5 hours, 48 minutes). It's probably enough to help you make it through a long meeting, but it won't necessarily help keep you going all day.
The Flux is the thinnest, lightest iPhone 7 battery case we've seen, and the fact that it doesn't cover up your phone's Lightning port is a definite plus. But it doesn't provide much protection, and you'll get a lot more battery life with a bigger case like the Slim Juicer, our Editors' Choice. If you want a battery case that won't weigh your pocket down, however, the Flux is worth a look. If you don't want to add any bulk to your phone at all, consider buying a portable backup battery.