The Secret Language of Charging Your Smartphone

In today’s world, it’s not uncommon for a family – or even one or two people in said family – to have any variety of smartphones, tablets, and chargers. It can be a problem when charging your smartphone! Thankfully, Android device manufacturers have settled around the micro-USB format for chargers, while Apple has come up with two formats on the phone end. The most common cables all use the USB format on the charging side though, so it seems like you can grab almost any charger and plug in any smartphone or tablet. But can you really?

The short answer is yes. There are a few asterisks that go with that short answer, of course, and they have to do with that seemingly secret language of electronics. Words like amperes and mAh which seem to create more questions than they answer. We’ll try to give you the simple versions, but keep in mind the simple answers apply mostly to newer devices; anything manufactured before 2010 has a better chance of not quite following these guidelines, and you’re likely to experience different outcomes. With that in mind, let’s decipher the secret language of charging your smartphone and tablet.

What’s an Amp and why does it matter?

Most smartphones are 1 Amp devices, while many tablets are 2 Amp devices. What does that mean? Think of Amps like speed limits for electricity. Your smartphone most likely charges at 1 Amp, about like traveling down a street with a 35mph speed limit. Can you go faster? Yes. Will it cause any damage? Probably not. Will you get there faster? Mostly likely, yes.

Your tablet is likely to take a 2 Amp charger. It’s a bigger device, so you might not be surprised to learn it likes a little more juice. Can you safely use your smartphone’s 1 Amp charger? Sure. Will it work as well? No, but sometimes any charge is a good charge.

So, what happens when you plug your smartphone into a 2 Amp charger? If you’ve heard the term “quick charge,” that’s about what you’ll experience. You are pumping in twice the power in the same amount of time, so your phone should charge up more quickly. In the short term, that is not likely to hurt your device or its battery, but the long term effect may be a reduction in your battery’s lifespan. Most agree, though, that it won’t be a huge difference.

And what happens when you plug a tablet, which is hoping for a 2 Amp charge, into your smartphone’s 1 Amp power cube? Exactly the opposite of a quick charge. Since you are feeding it half of what it needs, it’s going to take twice as long to fill up. No damage will occur, you’ll just need some extra patience.

That 1 Amp / 2 Amp deal holds true for most charging devices, like portable chargers and the small wall chargers that come with your devices. You can also charge up your device by plugging it into your laptop or computer’s USB port. However, computers can have two kinds of USB ports, only one of which will actually charge your devices. Some manufacturers will indicate a charging USB port with a small lightning bolt but, if one USB port doesn’t charge your phone, try plugging into one of the others.

So what’s the deal with mAH on battery-powered chargers?

There are a lot of battery powered portable chargers on the market. Basically, it’s a battery in a case with a USB port to plug your phone or tablet into, and a microUSB port to plug your charger into. You will find big numbers like 2600, 5200, 7800 or more, with the letters mAh next to them. What the heck?

mAh stands for millampere hour, and it’s a measure of how much stored electricity a battery can hold. So naturally, you want that number to be as big as possible! Unfortunately, the bigger that number is, the bigger and heavier the battery is, so it’s a bit of a balancing act. There are very small, lightweight battery-powered portable chargers in the 5200 to 7800 mAh range, which is enough to give an average smartphone two to four full charges.

You can do some simple math yourself to figure out how much you can get from such a charger. If your phone has a 2600 mAh battery, then a 5200 mAh back-up battery should give you two full charges. It’s easiest to think of these as being similar to a water pitcher and a glass. If you have a half-gallon pitcher (64 ounces), you can fill up your 8 ounce glass eight times. Battery-powered chargers work the same way to quench your smartphone’s thirst.

As an example, a Samsung Galaxy S5 battery has a capacity of 2,800 mAh, and an iPhone 5S battery has a capacity of 1,560 mAh, so both of these devices will get more than two full charges from a 7800 mAh battery-powered charger. An iPad 4 battery is huge by comparison, holding 11,560 mAh. Does that mean it will last longer? No, because the iPad 4 uses (or “draws”) more power than a smartphone.

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Why it’s hard to predict how long your battery will last.

The math seems simple enough but, of course, there is more to it than simple math. 1 mAh is enough to power a device drawing 1 milliamp for an hour, but how much power your smartphone or tablet draws is extremely variable. So many things contribute to the drain on your battery, including what sort of network you’re on (Wi-Fi, 3G, 4G), how bright your screen is, how many (and which) apps are running in the background, whether GPS or Bluetooth are turned on, and so on. Unless your device is in Airplane Mode, it’s probably got far more going on than you suspect.

You may already have a good idea how long your battery typically lasts. When I used a Samsung Galaxy S5, it would go a little more than 12 hours on a full charge. Since I know it has a 2800 mAH battery, the math tells me it’s drawing about 233 milliamps per hour (2800 mAh/12 hours). I also know that I use more features when I’m traveling, such as the camera, GPS, and travel apps, and I use them more frequently. That means my battery will not last as long. With a 2800 mAh battery, I can get a little more than 2.5 charges from the 7800 mAh back-up battery I recently purchased, assuming I let my battery go completely dead before charging. So, even if I have to charge up every six hours, it should get me through a day on the road.

Our best advice for charging your smartphone and tablet.

Now that we have demystified the world of charging your smartphone and tablet a little bit, we do have a bit of advice gleaned from our own experiences:

• Size Matters! Buy the largest battery-powered portable charger that you are comfortable with. There is a meeting point of price, size in mAh, and physical size and weight that you will be comfortable with. We recently picked up a few iFrogz Golite 7800 chargers for the crew because they met our collective requirements: 7800 mAh is enough to charge our phones 2+ times, or our tablets once, they weigh about 4 ounces each, and are pocket-sized. They have both one- and two-Amp ports, and can be charged with our existing wall chargers. There’s also a built-in flashlight that we’ve actually found useful. Plus, they were on sale for about $40 (retail $49.99). (Update: Since this article was written, iFrogz has introduced a more powerful (albeit, more expensive) charger. The iFrogz Gofuel 13,000 mAh portable charger is usually $55 or under at Amazon. We have not tried this one but, since the Golite 7800 we got is frequently out of stock, this seems like a worthy upgrade.)
• Amps…not so much. Don’t worry too much about the Amp rating of your portable chargers. Almost everything you’ll find today will be 2 Amps or less, as will your devices. And don’t worry about getting a “quick charge” for your smartphone by using the 2 Amp port marked for your tablet.
• Do Not Pass Charge Just like bathrooms and gas stations, never pass up a charging station. If you have a chance to plug in for a few minutes, do it. No one has ever said, “I wish I didn’t get that 15 minute charge at the airport.”

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