Choosing your battery

Modern gadgets are power hungry. If you want to make it through a long commute or a cross-country flight without having to plug your tablet or gaming device in, you’re going to need an external battery pack to keep the electrons flowing. Read on as i show you how to shop for a pack that will meet your needs and keep your screens glowing.

What’s an External Battery Pack and Why Do I Want One?

Normally when you need more juice for your smartphone, tablet, or other mobile electronic device, you plug the USB charging cable in to your computer or into a wall socket. You top the device off (or keep using it while it charges in the background) and away you go.

Instead of plugging your charging cable into the wall, you instead plug the charging cable into the battery pack and fill up the device’s batteries that way. Not all battery packs are created equal, however, and even if the build quality is good, you can easily end up with an external battery pack that doesn’t fit your application and power needs.

Estimating Your mAh

Before all else, you need to establish how much juice you need. Device batteries and external battery packs that top them off have capacities rated in mAh (milliampere hours). This is the principle measuring stick you’ll use to determine how much you need to invest in your pack.

First, gather up the devices you want to charge off the external battery pack. Let’s say, for the sake of example, you have Samsung’s popular SIII smartphone and a new iPad Air. The SIII has a stock battery with a capacity of 2100 mAh and the iPad Air has a stock battery with a capacity of 11, 560 mAh. Now it’s time for a little number crunching.

You can use the following equation to determine just how beefy of a battery pack you need:

(Total mAh) * (% battery life extension expressed in decimal format) = Pack Size

If you wanted a battery pack that could double the battery life of both your devices, you’d need a pack with a capacity of at least 13,660 mAh:

If you wanted to squeeze 50 percent more life out of them, you’d need a device with at least a capacity of 6,830 mAh. If you only cared about keeping your iPad going during your flight and you’d have your phone turned off, then you could stick with a battery pack that had around the 11,560 mAh capacity of the iPad to double its life.

Just like in every other battery application, there’s a trade off to be had between high and low capacity devices, and that takes the form of weight. The a lipstick-sized battery might only have 2,000 or so mAh in them, but they only weigh a few grams and easily slip into your pocket or purse. Our 14,000 mAh beefcake that can keep your iPad running over a trans-continental flight? It weighs 310g or so and won’t be very comfortable in your pocket.

Selecting the Right Amperage

In addition to calculating how much battery capacity you need, there’s also the matter of charging amperage. The bigger and more power-hungry your device, the more important having the proper amperage on the USB charging ports is.

Charging ports on battery packs, like charging ports on wall-warts and computers, can provide electricity at different amperage rates say 1A and 2.1A. All USB devices can use both ports, but if a device can only handle 1A of power then it will automatically limit itself to 1A on a 2.1A port and if a 2.1A device is on a 1A port it will also charge (but at a much slower rate).

For trickle charging, such as you might do overnight or if you just had the device sitting in your briefcase hooked up to the battery pack, the amperage doesn’t matter as much. Yes the 2.1A will charge the device faster, but if you’re not using it and it’s just topping off the device, the speed of the charge isn’t such a big deal.

Where the amperage becomes critical is when you’re shopping for a battery pack that you intend to use on a battery-hungry device while the device is in use. For example, if you want a battery pack that can keep an iPad Air topped off while you’re playing a graphics-intensive video game or otherwise taxing the system, you’re going to need, no questions asked, a battery pack with a 2.1A charging port. Packs with 1A ports simply won’t be able to keep up; you’ll be burning battery life on the device faster than the battery pack can replace it.

Ports for Your Pals

If you’re shopping for just yourself, it’s OK to spend less and get a device with a single port or a 2.1A and 1A port. Need to provide a steady flow of juice to both your iPad and your traveling companion’s iPad, though? You’d better spend the extra money to get a battery pack with two high draw 2A ports. If you’re planning on setting up a multiplayer gaming huddle at 30,000 feet, you can even find battery packs with 4+ 2.1A ports.

Given that it doesn’t cost much more to get a better pack with an extra port or two, you’ll come off looking like a very prepared spouse or business partner if you have some juice to share with your travel mates.

Extras Worthwhile and Worthless

Because the external battery pack market is pretty heavily saturated, many manufacturers have started including little extras to entice buyers. My advice is to avoid being swayed by the extras unless the extras offer you high-utility or save you money. For example, if the pack you’re looking at costs an extra dollar and comes with an iPad charging cable, and you were planning on buying one anyway, that’s a good value. If it costs a lot more and comes with 12 adapters for crap you don’t even own, then it’s not such a hot buy.