#1 By: Chris Hoffman, November 19th, 2013 06:40
Originally published at: http://www.howtogeek.com/175734/htg-explains-can-you-use-any-charger-with-any-device/
Every device — smartphone, tablet, eReader, laptop — seems to come with its own charger. But do you really need all these chargers? Can you re-use the same charger for multiple devices?
#2 By: Naman Sood, November 19th, 2013 10:42
Warning: If you have a Sony Xperia device, do not use another charger. Using my Nexus 7's charger on my Xperia E caused the battery to go hyperactive and stop working. Sony replaced the battery, but another charger may still be dangerous.
#3 By: Vincent Boswell, November 19th, 2013 11:56
I am pretty sure this sentence "If you’re travelling intentionally, you’ll need to know . . ." should read "If you’re travelling internationally, you’ll need to know . . ." So far all of my travel has been intentional, thank goodness
#4 By: Paul Silvan, November 19th, 2013 12:04
Nothing was mentioned about overcharging. My phone often beeps when fully charged to tell me that charging is complete and I should disconnect from the power source. I usually charge my devices overnight and leave them connected until morning. Is there a danger of ruining batteries by allowing the device to remain plugged in? If the charge reduces to a trickle, is that a function of the device or the charger?
#5 By: Tom Wilson, November 19th, 2013 12:21
This article has missed something very important: while most cell phones charge just fine with any 500ma USB port, that does not hold true for tablets. tablets won't work with generic USB chargers.
The tl;dr explanation: use a branded charger with your tablet. iPads should use Apple branded (or logo'd) chargers with at least 1000ma output. Samsung tablets will only charge from Samsung chargers. With others, it's kind of random.
The long version:
The good news is that your mobile phone will usually work just fine when plugged in to any USB charger: 500ma will charge a typical cell phone battery in around 2-4 hours. The bad news is that tablets actually draw more than 500ma when they're running, so tablets charge very, very slowly on a generic charger, if they charge at all. The iPad's battery? It would take at least 12 hours to charge off a 500ma power source.
The problem is that there's no way of actually knowing how much current an electrical circuit can safely provide. So manufacturers have settled on the practice of putting a small voltage on the center 2 pins of the USB cable. The device senses this voltage and uses that to tell its internal charging circuitry how much current to draw from the USB jack.
The problem with that approach is that the standard isn't universally followed. Apple and Samsung both use different voltages to tell their devices that they're plugged in to a 2000ma charger.
My iPad will only reliably charge from a 2000ma power adapter that says "iPad" on the packaging. My Samsung tablet would only charge from a Samsung charger. Plug it in to a PC, an iPad charger, or my Motorola adapter, and it says "Not Charging" next to the battery.
My Nexus 7? Same deal: it charged reliably from Asus chargers (Asus makes the N7), but not from others. I finally found a $10 usb power adapter that worked in the car, but that was after trying and returning half a dozen others.
So the short version of all this: if you buy a tablet, buy a spare charger (or two) from the same company. It's the only reliable way to keep your tablet juiced up when and where you need it.
#6 By: Tom Wilson, November 19th, 2013 12:26
Is there a danger of ruining batteries by allowing the device to remain plugged in?
Absolutely not. All Lithium-ion batteries (which includes the Lithium-polymer batteries in all cell phones and tablets) require that the charger stops charging at the battery's peak safe voltage, which is typically 4.2 volts per cell. In fact, the "unplug your device to save power" thing is exactly wrong, as your phone uses exactly the same amount of power whether it's plugged in to the wall or not. It simply draws the power from the battery when it's not plugged in. And since the battery needs to be charged, and no charging process is 100% efficient, you're actually wasting energy by unplugging your device.
If the charge reduces to a trickle, is that a function of the device or the charger?
Trickle charging refers to the process of keeping a battery topped off by running a small current, such as 10ma, through it. Lithium batteries cannot be "trickle charged," or they will explode. Instead, a proper lithium charger will check the battery's voltage periodically and keep it topped off.
And the term "charger" is misleading: the thing you plug in to the wall is a power adapter or power supply. The charger is actually inside the phone (or tablet or MP3 player.) The power adapter just supplies a constant voltage. Aside from that, it doesn't have anything to do with actually charging the battery.
#8 By: Rick P., November 19th, 2013 19:43
Proprietary electronic devices have always been a mess. (lol) (lol)
#9 By: Naman Sood, November 20th, 2013 05:11
Wouldn't that apply for flagship phones as well? The Galaxy Note 3 (or S4) has an octa-core processor, a 1080p screen and 3 GB (2 in S4's case) of RAM to fill up with apps. I'm assuming here too we should use the standard 2A charger that comes with the device.
#10 By: Tom Wilson, November 20th, 2013 11:55
Not really. The SGS4 and Galaxy Note batteries are around 2500 mAh, and the SGS4 can be "screen on" for a good 8-10 hours on a charge. This adds up to less than 300mA of current draw, more than enough for a generic charger to keep it topped off while driving or at the office.
The difference is all about current draw: the iPad "up to" 10 hours of battery life while web surfing or watching videos. With a battery capacity of around 6000mAh on the first gen, that equates to 600mA of current draw - more than a 500mA charger can support. Again, this is consistent with my findings: I could only charge my first gen iPad with a 1-amp or larger car adapter and with the 2-amp Apple supplied wall adapter.
While it's not ideal, the Galaxy note and SGS4 should work fine on generic power adapters, even if it takes a little longer to charge.
The math is very simple to do: divide the battery's mAh capacity by the reported battery life. If people are saying you can get 8 hours out of a device with a 2500mAh battery, that's a 312mA draw. If that's significantly less than 500mA, you can probably charge it with a generic charger - even with the screen on and the device doing stuff.
And - as usual - your mileage may vary. There are some devices that just plain won't charge on anything but a logo-certified power adapter. The real answer in all this is really very simple: just try it. If it works, it works. If not, go spend the $30 on a name-brand power adapter.
#11 By: Naman Sood, November 21st, 2013 05:15
But then that would mean I can charge the Nexus 7 (old one) on a 500 mAh charger. The battery is 4325 mAh (according to Wikipedia) and is expected to last ~9-10 hours (also according to Wikipedia). That amounts to a maximum of a 480.5 mAh power draw.
#12 By: Tom Wilson, November 21st, 2013 10:04
I already said that tablets should only be used with the logo'd power adapters, didn't I? The Nexus 7 is no exception.
It will actually charge from a 500mA power adapter, but it does so VERY slowly when the screen is off. When the screen is ON, the charger just barely keeps up - it keeps the battery from discharging while the tablet is being used, but that's about it.
#13 By: Naman Sood, November 21st, 2013 11:55
Okay... I'll just take my own sweet time trying to figure that out. Don't worry about me.
#14 By: system, November 29th, 2013 06:40
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