When you’re on the road, your phone usually ends up performing at least quadruple duty. It's your camera, map, in-flight entertainment system, communication device, and who knows what else. You could carry a portable power bank to fight off battery drain, but then you have to remember the pack and its cords, which might start to weigh down your bag — and that’s all assuming you remembered to charge it in the first place. Built-in battery cases, on the other hand, will take out all of the guesswork so you won’t be stuck in a foreign country without a way to look up the word for “bathroom” when you need it most.
Battery cases work by passing power through the case rather than through a wall charger, explained Chad Taylor, a technology expert at Abt Electronics. “The difference is: The more premium brands have better hardware and software that does not allow the device to overcharge the phone or tablet,” Taylor said. “They also use better batteries that are tested. Make sure you have a product that does not overcharge your phone.”
Most cases charge both themselves and your phone via one input, so you can just plug the combination in overnight and you’ll have two full batteries ready to go by morning.
The other key piece to pay attention to when looking for a charging phone case is milliamp hours, or mAh, a measure of energy capacity. The more mAh your battery has, the more power it can hold, and the more phone charges you’ll get out of it. 2400 mAh equates to about 33 hours of extra battery life according to Taylor, depending on what you’re doing. Though in many cases, more mAh also means a larger battery and therefore a bulkier case.
If you opt for a sleeker case with less power, you can conserve your battery by keeping your phone in airplane mode when you aren’t actively using it and disabling unnecessary notifications, which consumer education and travel writer Janice S. Lintz recommends. Choose a case that won’t add too much additional weight to your phone and is easy to use. Whether you want a bright color for easy spotting in your bag or a darker one to blend in with the crowd is up to you.
If you have an iPhone, you may want to make sure your case is MFi (Made for iPhone/iPod/iPad) certified, the official Apple seal of approval for accessory compatibility. It’s not mandatory, but it is helpful if you’re worried about non-compatible cases potentially damaging your phone.