Anyone that uses a cell phone, laptop or other gadget can understand the usefulness of a battery re-charger, especially in an emergency. In fact, anyone that uses electronics that constantly eat up alkaline double AA or triple AAA batteries will appreciate the cost savings that comes from buying rechargeable batteries and a rapid recharging unit. These days many people, including myself, have become quite dependent upon small electronic gadgets and devices. If this describes you, you have probably needed some type of portable power source to keep all your devices powered up at some point.
AA USB chargers can refer to both USB-to-AA and AA-to-USB chargers. Make sure you know which one you want and which one it is you're going to buy! Some products can do both - the latter will be covered first. Read on for more information about some of your options when it comes to getting a fast recharge for your devices, without having to plug into an electrical wall socket.
There are two basic types of chargers that you can find on the market to power up small batteries, such as lithium ion types used in mobile phones. The first is a recharging unit that holds fully charged AA cells, which then provides electricity via a universal USB plug to multiple devices like your smartphone, tablet or e-reader. Put a few batteries into this type of charging unit, plug it into your device's charging socket and top it up. This makes a smart, cheap solution during power outages, for travel such as camping trips or other times when you will not have access to electrical outlets for an extended time period. There are also specialty models that look like an actual AA or AAA battery, with a top that pops off to reveal a USB plug. Recharge by plugging into your laptop, then pop the entire thing whole into any device that uses this size of battery and you are ready to roll.
Sometimes, you need a device that works the other way. You can find units that allow you to put your AA and other small nimh batteries into a casing that plugs into your computer's USB outlet. This allows you to use your computer to refresh your ni-mh batteries, usually from 1.2 to 12 volt, then use these batteries when you are away from your computer to recharge your other devices. This becomes extremely helpful when you often find yourself stuck on an airplane with a dead smartphone or tablet, or have forgotten your phone adapter while traveling.
You can also find solar powered charging devices. No need for any electricity at all here -- just lie the unit's panel in the sun, throw in a bunch of AA cells and allow time for them to become fully topped up with the help of solar power. And of course there are models that allow you to plug it into almost any USB or micro USB device to refill them in the same way too. How intelligent is that? You can lay in on the dash of your car while driving, for a quick re-charge of your gadget. You can also find chargers that provide power through the use of a hand crank. Although these chargers are a bit large, they require absolutely no other source of power (solar or otherwise) to operate.