You're packing for a trip. You've already crammed the chargers for your smartphone and laptop into your bag, but your tablet charger is MIA and you're debating whether to bring along a spare charger for your laptop--just in case.
Then you ask yourself: "Do I really need to bring them all? Wouldn't one or two chargers do the trick?"
Hmmm, would they? After all, users can charge most phones and tablets these days via a Micro-USB cable and a reliable source of electricity.
We challenged the TechHive Lab to find out whether chargers could switch phone or tablet models and still charge successfully, and the guys there rose to the challenge. Here's what they found.
Speedy charging
To find the quickest way to charge a smartphone or tablet, we tested how long it would take to charge two of each (the phones were an iPhone 5 and a Samsung Galaxy S III, and the tablets were an iPad 4 and a Samsung Galaxy Note 10.1).
We used several power sources in our tests, including the original charger for each phone or tablet and the USB ports of a Mac and a Windows 7 laptop.
We also charged the two phones using each other's charger, and did the same for the two tablets, to see how long they took to get fully charged.
And the winner is...
Generally the quickest charging time comes when you use the charger that originally came with your phone or tablet.
For three of the four devices we tested, the original charger worked the fastest--often by a considerable margin--to charge its companion device.
The only exception was the Samsung Galaxy S III, whose charging times with its charger and with the iPhone 5's charger were so close that the lab proclaimed the results a virtual tie.
We were surprised at how slowly some devices charged with an alien charger.
For instance, the iPad 4 took 19 hours, 13 minutes to charge when we used the charger designed for the Samsung tablet--that's more than triple the amount of time the iPad took to charge when we used its own charger.
The upshot: If you travel without all of your original chargers, you could be looking at a looooong wait to get a phone or tablet fully charged.
All of these phones and tablets contain circuits that detect the connected device: if it isn't one of their own, they deliver a lesser flow of power to avoid frying the device. That's a prudent precaution, perhaps, but annoying to the owner lugging around a heavy clutch of power bricks.
Don't mix chargers when a tablet is involved
Are you tempted to use your iPhone charger to charge your iPad? Feel free to do so, but only if you have 10 or 15 hours to spare.
We tried using chargers designed for phones on tablets, and vice versa. The phones had no problem drawing juice from the tablet chargers, but the tablets didn't respond well to the phone chargers.
The Samsung Note 10.1 was the worst here--it took an epic 15 hours, 29 minutes to charge using the Samsung Galaxy S III charger. But the iPad wasn't much better; it took over 10 hours to charge with the iPhone 5 charger.
The main problem here was simply the amount of juice available. Whereas the iPad charger delivers a hefty 2100mA of current, the iPhone charger can muster only 1000mA. This makes charging the iPad's massive battery of the iPad rather like carving out the Grand Canyon with a seasonal stream: it works, eventually, but it requires a lot of patience.
Not all USB ports are created equal
When it comes to charging a phone or tablet from a USB port, not all USB ports perform equally well.
We charged our phones and tablets from the USB ports of a Windows laptop (a Lenovo ThinkPad Twist S230u) and a MacBook Air--and found that they tended to charge our mobile devices quite slowly.
The Samsung Galaxy S III we tested took more than 5 hours to charge via the laptops, while the iPhone 5 took between 2 and 3 hours. That's because the iPhone 5 has a smaller battery than the Galaxy S III (1400mAh versus the Samsung's 2100mAh). Windows reported that both devices were drawing 500mA of power while charging.
This situation became more complex with the power-hungry tablets. The iPad took just 6 hours to charge from the MacBook Air's USB port, but it needed more than 25 hours to charge fully when hooked up to the Lenovo ThinkPad's USB port.
That's because Apple phones and tablets can request more power (up to 1100mA) from the USB ports of Apple devices This neat trick only works with Apple products, however: The Samsung Note 10.1 took more than 15 hours to charge from the same USB ports.
USB 2.0 ports on laptops can deliver 500mA (increased to 900mAh for USB 3.0), but only if the device requests it.
Otherwise, they deliver about 100mAh, to keep from overloading the device. The faster-charging feature is available on some recent PCs and is usually referred to as a high-current USB port.
Check your laptop's manual to see which (if any) USB devices offer this feature and how to identify a high-current port.
Unless you're using only Apple devices, its unwise to trust the USB ports of your laptop to charge your mobile devices within a reasonable amount of time. They'll do the job if you don't have your mobile device's original charger with you, but it will take a long time.
Use your original charger
Our tests show that you'll get the quickest charge from the charger that came with your device. However, if you want to take only one charger with you on a trip to charge both an iPhone and an iPad, choose the more-powerful iPad charger instead of the weaker iPhone charger.
For other devices, use a charger that the manufacturer has tested and verified with your particular mobile device. Most charger manufacturers produce a compatibility list for their products.
Some new technologies on the horizon could speed things up even more. For example, Qualcomm recently announced the new Quick Charge 2.0 standard, which will allow the charger to send a hefty 4 Amps (4000mA) of power. To use this technology, you'll have to work with a special charger and a phone or tablet that supports the standard.
