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Charger Compatibility - 550mA vs. 700mA

I have older chargers for that output 5.0v / 550mA and have noticed that the Captivate outputs 5.0v / 700mA.
1. Can I safely use the older, 550mA chargers with the Captivate and what will the effect be?
2. Can I safely use the Captivate's 700mA charger with the older phones and what will the effect be?
Thanks.

1. Yes, you can use it. But it will charge slower.
2. Yes, you can use it. I believe that just because the charger output is higher amperage doesn't mean that it will affect the phone adversely. Think of it this way: A lamp is plugged into the wall outlet at your house. That outlet is rated at 120v 15A. The bulb isn't using all 15 amps, so no problem. But if you were to turn the voltage up or down, the lamp will get brighter or dimmer respectively.
The Captivate can take up to a 1A (1000 mA) charger.

Truceda said:
1. Yes, you can use it. But it will charge slower.
2. Yes, you can use it. I believe that just because the charger output is higher amperage doesn't mean that it will affect the phone adversely. Think of it this way: A lamp is plugged into the wall outlet at your house. That outlet is rated at 120v 15A. The bulb isn't using all 15 amps, so no problem. But if you were to turn the voltage up or down, the lamp will get brighter or dimmer respectively.
The Captivate can take up to a 1A (1000 mA) charger.
Click to expand...
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Another question. You sound smart on this so how about using the nexus one car charger on this? Fits perfect and I don't see why not, but still Leary. .. what do you think?

As long as it puts out 5v, (which is USB standard), you are fine. The amperage is only relevant if the device REQUIRES it. For instance if the device draws 1A and your charger could only handle 550mA your device will charge very slowly.
On the other hand if your charger can handle 1.2A and your device only draws 700mA, then your charger will only output 700mA.
The important thing is the voltage, it needs to be 5v +/- 3% ...
I actually use a generic car charger I bought at walmart with 2 USB ports on it, and it works well for every USB powered device I own ... ZUNE, iPOD, phones etc.

OK. Thanks for the reply. I had read that a phone requiring 700mA that uses a 550mA charger could damage the charger and possibly the phone. That's what made me wonder. And that's what led to the question.
Let's make this a bit more interesting. There's a local, highly-reputable cell phone repair store that has stopped selling car chargers because, they say, the rapid charge is not good for the phone's battery. Their recommendation is to use an inverter (no, they don't sell them) so that you can then plug a standard wall charger into it or a USB cable if the inverter is so equipped. The AC current that results from utilizing the inverter is more consistent than the current flowing from a car charger. So...I purchased an inverter for less than $20 and use it to charge the Captivate in my car.

OK ... not sure we need to get this far down in the weeds on this but here goes ....
The USB2 standard for power distribution is 5v and the thresholds are 4.4-5.25V.
Power is supplied in units of 5v power ... 1 unit is 5v at 100mA, no device can draw more than 5 units from any one port. If you have ever seen a portable hard drive with 2 USB connectors it is because it requires more than 500mA to operate and by using 2 ports the device can draw up to 1A. For dedicated chargers the 4.4-5.25v still applies but shorting the D+/- and disabling the data connection allows the device to detect that it is connected to a dedicated charging port and draw a maximum of 1.8A.
In keeping with the above guidelines, when connected to your computer the Captivate can draw no more than 1 unit of power which is [email protected], when connected to a dedicated charger the phone can draw [email protected] and stay within the standard. (yes, it caps itself at 1A, I know).
OK ... the next bit is going to be hard to digest because there are plenty of examples to the contrary ... there is a standard for mobile USB chargers, and it requires wiring them as dedicated charging ports. What this means to us is that, in theory anyway, a mobile USB charger should allow a device to draw up to 1.8A from it (highly unlikely ... but that's the standard as written).
Here is the problem, if the device is plugged into a dedicated charging port and tries to draw it's maximum rated current, that amount of current may not always be available or it may fluctuate. This fluctuation is what causes problems. Have you ever turned you car stereo up real loud and seen your headlights dim in beat with the music? Same thing, the power system is being drawn down. There are a couple of ways to stabalize your power system ... install a large capacitor (mine is 2 Farad) to provide "conditioning", or go the transformer route.A tansformer provides conditioning, but only on its own outputs... while a large cap will condition the entire power system if installed correctly.
So yes, using a quick charger on your phone can cause issues if your car has a ****ty power system or a large stereo system which is not set up properly (again, ****ty power system). Make sure your charging device is within the standard, and you should be fine wether it is USB via a cigarette lighter port or a 110V transformer.

I appreciate your detailed, helpful reply.
Other than the important 5v parameter, what I've taken away from your information is that a car charger can be used in a vehicle with a power supply that is known to be stable, and that either a whole-car conditioning system or an inverter should be used on one with a, shall we say, "less than stable" power supply (PG version ).

Jack45 said:
I appreciate your detailed, helpful reply.
Other than the important 5v parameter, what I've taken away from your information is that a car charger can be used in a vehicle with a power supply that is known to be stable, and that either a whole-car conditioning system or an inverter should be used on one with a, shall we say, "less than stable" power supply (PG version ).
Click to expand...
Click to collapse
Pretty much ...
There's more than one way to skin a cat, and that Transformer will cost you a whole lot less than a 2 Farad capacitor. I hate cats, but they serve a purpose.

@Battlehymn - one more question for you
I have converted from iPhone to the captivate (no haters please) - finally found a physical form factor with specs i like and the captivate rocks.
Anyway, I have some extra external batteries I used with my iphone that i want to use with my Captivate. I just bought a Female iPod connector and I am planning to connect it to a micro USB connector - the pinout is straight forward, but here is my question:
Should I connect the D+/- (short them together)? That is my plan. My batteries are 1900 or 1000 mAH - I assume that even if the phone tries to the draw 1.8A, the batteries have a circuit to only discharge so fast.

[Q] Alternative chargers, voltages and mAmps

Hi all,
I have various chargers at home for the various pieces of kit we have.
My Asus Transformer tf101 has a charger which outputs at 15V, 1.2A
We have other chargers for phones & another tablet all with usb sockets on them.
An HTC outputs 5V, 1A
An Alcatel outputs 5V, 350mA
A Lenovo outputs 5V, 1.5A
Can anyone confirm my understanding about which charger to use and when, please?
I believe that if I use a charger with a LOWER voltage & amerage output than that delivered by the dedicated device charger, that it will NOT damage the device I charge with it - but it will probably take longer to charge. Is this correct?
So I shouldn't use my tf101 charger with anything other than my transformer tablet because it is 15v. But would it be OK to mix any of the other chargers around as they are all 5V? EG could I safely use the HTC charger on the Lenovo? Does the output amperage figure matter, or just the voltage?
Presumably I could use the 5V chargers on the tf101 - but it would take 3 times longer to charge? Could I use the Lenovo charger on the tf101 or would the higher amperage damage the transformer, even though the voltage is lower.
Advice please, helpful members

janner43 said:
I believe that if I use a charger with a LOWER voltage & amerage output than that delivered by the dedicated device charger, that it will NOT damage the device I charge with it - but it will probably take longer to charge. Is this correct?
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Click to collapse
This is my understanding: I believe it to be correct, but I may be wrong.
You must match voltages, if you use a charger with too low a voltage, it won't damage the device, but it won't work either. If it's too high, that would potentially damage the device and not work.
You need not match amperages (current) but in order for it to work correctly, you must use a charger greater than or equal to the rated current, eg., if the device wants 3A and you supply 5, this _should_ be OK, as the device only draws 3. But if it's _too_ high and you may exceed cabling tolerances, as the cables are only designed to handle current up to a certain amount, but I won't worry about this unless you're intending to supply currents >10A, say.

You can't charge a 15 volt device with 5 volts you could leave it charging for a million years and it would still only be 5 volts.
You can't charge a 5 volt device with 15 volts or you will cook the electronic components inside.
Another thing to remember the plugs used for different devices will be different sizes. The charging voltage's are usually direct current (DC) with a positive and a negative so you must make sure that the connections are correct.
As for the current rating's of the other chargers my experiance has showed me that isn't quite as important, as the current rating listed on the label is the maximum current that the power supply should have taken out of it.....
If you need to know more about basic electronics there is plenty of sources of information if you search Google.
Sent from my HTC Legend using XDA App

You should always use a charger with same volts of the stock one. The amps is relative, it will determine how fast it "delivers" the current, so the greater it is, the faster it charges...

Question about chargers

I have an HTC Explorer, which came with a USB cable and an adapter to allow me to charge via mains as well. (Something like this: http://i.expansys.com/i/g/g232723.jpg - that's not the exact same one, but you get the idea). This charger says on it that it has an output of 5V and 1A. I also have a Blackberry Playbook, which came with a charger with a micro USB connector. However, this charger says on it that it has an output of 5V and 2A.
I have tested the HTC charger with my playbook, and it worked, but the question I want to ask is this: would it be dangerous to try the playbook charger on my HTC phone? (2A output from Playbook charger versus the presumably expected 1A input on the phone) I would like to be able to only carry one charger when travelling and the playbook charger has interchangeable adapters for international plugs, so it would be better to take, but obviously I don't want to overload the phone and have it burst into flames or whatever.
Any advice on the matter would be great, thanks.

It's not recommended by the manufacturer. It can void your warranty, though I don't know how they'd ever find out you were doing so. There can also be issues when using the cable to transfer data and such.

I did watch a video about that Blackberry charger.
Supposedly because of that 2A output, it charges your phone twice as a fast.
Sent from my Ainol Novo7 Elf using xda premium

I don't think there would be considerable damages but..I'd just use them both, even if it's less comfortable

I looked around and I think it should be safe. From what I've read online, the phone will only take a certain amount of current, regardless of the current being made available by the charger. Because the voltage is the same (5V), and the resistance of the phone circuitry is constant, by Ohm's law, I = V/R, so I will always be the same as long as V is the same. Presumably it'll drop with a lower input current, but the max I will always be the same, and that'll be limited to a safe level.
It might take a slightly higher current (say if the max the phone can take is 1.2A or something, the 1A charger can only give 1A but the 2A would give the full 1.2A), but no higher than the circuits in the phone will allow. After reading this, I realised that it made a lot of sense, and I think it's right. I also read that if it does charge the phone faster (which it will if the phone is taking a higher current e.g. 1.2A) it'll reduce the number of charging cycles that you get out of the battery. But the consensus seems to be that doing it every now and again when travelling etc. should be fine.
Thanks for all your responses.
EDIT: I think at worst, I might damage the battery, and they're not overly expensive to replace I don't think.

I agree, the rating on the charger is what it's MAX output, not that it will push that much current to your device. If you have an extra USB cable (that you dont mind cutting apart) and a mulit-meter, you can check to see how much current your phone is pulling from the BB Playbook charger. connect your mult-meter in-line with the red wire in the usb cable (just connect all others together)
Just make sure your mult-meter is rated for at least 2A.
Hope this helps.

Devices with lithium batteries usually have a charger circuit that limit the peak current that is sent to the battery. They also utilize temperature compensation so if you are charging the battery too fast, it starts limiting the charge current.
Where you might have a problem is when it's plugged in and you are using it, especially if the battery is low. You get high charge currents, combined with the operating current.

[Resolved] Can i charge headphones with higher mA without issues?

I spent much time to research, ask sony support, google... but i dont have answer yet...
I have got: (Everything is 5.0VDC)
Xperia Tablet Z (It comes with 1500mA charger)
MDR1-RBT BT Headphones (It comes with no charger, charge only via USB PC port - 500mA?)
MW600 BT Headset (It comes with 350mA cherger)
Can i charge all with 1500mA charger without ANY issues?
Please help me i can't get answer for long...

Please help.

BUMP

It'll eventually damage it
Sent from my Karbonn A15 using XDA Premium 4 mobile app

Will damage the headphones
Sent from my GT-I9100G using xda app-developers app

arvin07143 said:
Will damage the headphones
Sent from my GT-I9100G using xda app-developers app
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So i can charge it only via USB to PC?
Sony supporter said i can charge it with adaptor with specs 1500mA...
I don't understand it at all...

BUMP!

This one is not quite so straightforward without knowing about the internal circuitry of those devices you have in regards to how they charge.
Now, in general, it is safe to say that you must always match the voltage and polarity of the device you are charging, often you can use a higher rated current charger or power supply.
Why?
A device typically only draws how many amps it needs in order to function.
Take your TV for example, it probably only needs 2-3 amps to run yet it is plugged straight into the mains which has the capability of supplying many hundred of amps yet your TV doesn't "fry", it simply draws what it needs.
When it comes to charging its a bit more complicated and depends on the device (does it have internal charging circuitry or is the the item you plug into the wall and actual charger and not simply an AC/DC converter).
Most small electronics which contain a battery and are simply supplied with an AC/DC converter, say, Input 120V 1A output 5V 100ma have their own current regulating charging circuitry inside. This means that the thing you plug into the wall isn't actually a charger, its an AC/DC converter.
In that case the converter can have a higher rated amp output than your device states it needs because your device will only draw what it wants.
If what you are plugging into the wall is an actual charger which has the job of regulating the current flow to the device that needs charging then you will want to get one as close to spec as the original so as not to damage your device.
All the devices you list seem to charge via 5V, most likely a USB type interface.
This means that they are not supplied with actual chargers, simply power supplies, the charging and current limiting mechanism is inside each device.
In theory therefore you should be able to 'charge' all your devices via the 1500mA AC/DC converter, the products you have will only draw what they need in order to charge, the 1500mA will not be pushed or forced upon each device.
Also, think of this, you have been smart and come to ask for advice, how many people simply use the USB 'charger' of their husband/wife/sister/brother to charge their phone or product when they can't find their own and those devices aren't damaged.
The only thing is if the current is too low then it will either not charge or take much longer.
I hope that helps.

zasy99 said:
This one is not quite so straightforward without knowing about the internal circuitry of those devices you have in regards to how they charge.
Now, in general, it is safe to say that you must always match the voltage and polarity of the device you are charging, often you can use a higher rated current charger or power supply.
Why?
A device typically only draws how many amps it needs in order to function.
Take your TV for example, it probably only needs 2-3 amps to run yet it is plugged straight into the mains which has the capability of supplying many hundred of amps yet your TV doesn't "fry", it simply draws what it needs.
When it comes to charging its a bit more complicated and depends on the device (does it have internal charging circuitry or is the the item you plug into the wall and actual charger and not simply an AC/DC converter).
Most small electronics which contain a battery and are simply supplied with an AC/DC converter, say, Input 120V 1A output 5V 100ma have their own current regulating charging circuitry inside. This means that the thing you plug into the wall isn't actually a charger, its an AC/DC converter.
In that case the converter can have a higher rated amp output than your device states it needs because your device will only draw what it wants.
If what you are plugging into the wall is an actual charger which has the job of regulating the current flow to the device that needs charging then you will want to get one as close to spec as the original so as not to damage your device.
All the devices you list seem to charge via 5V, most likely a USB type interface.
This means that they are not supplied with actual chargers, simply power supplies, the charging and current limiting mechanism is inside each device.
In theory therefore you should be able to 'charge' all your devices via the 1500mA AC/DC converter, the products you have will only draw what they need in order to charge, the 1500mA will not be pushed or forced upon each device.
Also, think of this, you have been smart and come to ask for advice, how many people simply use the USB 'charger' of their husband/wife/sister/brother to charge their phone or product when they can't find their own and those devices aren't damaged.
The only thing is if the current is too low then it will either not charge or take much longer.
I hope that helps.
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I know that Xperia tablets and phones won't take more mA than it needs but does MDR1-RBT has the same thing? I did a lot of research but i still can't find the 100% answer. I don't want to try unless 100% sure. (Its expensive headphones)
EDIT:
Few sony supporters said: You can charge it only via USB cabble to Personal computer
Few sony supporters said: You can charge it only via USB cabble to PC or Adaptor (Linked me to USB/AC Adaptor with THE SAME specs like XTZ charger - 1500 mA)
Is Adaptor same as XTZ?
I found this on OFFICIAL Sony eSupport
http://docs.esupport.sony.com/portable/MDR1RBT_guide/en/contents/01/03/01/01.html?search=charg
OFFICIAL TIPS:
Tips
If the micro-USB cable is connected to a computer while the headset is turned on, the headset will be turned off automatically.
To charge the headset from an AC outlet, use USB Charging AC Power Adaptor* (sold separately). For details, refer to the manuals supplied with the USB Charging AC Power Adaptor.
The headset cannot be turned on while charging the battery.
* Refer to the Reference Guide on the recommended adapter.
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Click to collapse

BUMP

Zas99 answer is spot on.once the voltage matches to your device your ok.most phone chargers you can pull out the usb charging cable. u could use that or buy a another usb charger at 1500ma to 2000ma.
Sent from my HTC Desire S using xda premium

E7ite: You should be fine, the fact that it charges via USB means that it must have its own internal charging circuitry.
I bet your Xperia tablet also charges via a USB type cable right, on a USB port?
All my USB 'chargers' have different mA rating yet they charge my products just fine as long as the mA rating is at LEAST what the device needs, not less, and hey, if its a little less it also works, just takes longer.
Look at it this way, the USB specs are always changing as is their current handling capability, now we are at USB 3.1, just recently we were at USB 3.0 which bumped up maximum device current usage during data transmission to 900mA or for dedicated charging 1.5A.
For USB 1.x - 2.0 it was 100mA before negotiation, up to 500mA thereafter, also with a dedicated charging capacity of 1.5A if the D- & D+ pins are shorted.
I bet Sony doesn't tell you that you can only charge via a USB 1.x - 2.0 port do they? Nope, that means if your computer has a USB 3 port that its has the potential to deliver more, remember, that's the key, it CAN deliver more if needed but it won't, it will only give the device what it draws.
The cable they supply with your headphone is most likely not a data cable but rather a so called charging cable so therefore is rated up to 1.5A or 1500mA but your headphones will only draw what they need to charge.
Everyone uses the term charger which is so wrong, when you put your AA or AAA batteries into the little black box and plug it into a wall, that is a charger, when you connect your car battery via the +/- terminals and clamps to the charger, that is also a real charger, they are directly responsible for charging the batteries.
All these other things we use to 'charge' our little electronic devices do nothing other than take the 120V A/C and convert it into for example 5V DC. The current rating they indicate next to the 5V is simply the max current handling capability, nothing more, it not what is pushed to the device, its what the device can request up to to be delivered. The actual charging goes on inside the device.
By the way, as the batteries charge the device reduces the current and sometimes also the voltage, batteries typically charge faster when they are low and able to absorb more current then as they fill up and can absorb less the charger adjusts to a more or less trickle such as 100mA or less in order to maintain but not overcharge the battery.
By the way, this is what I found on Amazon in about 2 minutes, a review from someone else who bought the headphones.
"For the price, sony should have included a wall charger. Instead they included a USB cable. The headphones will charge on any computer, but using a generic USB wall charger will show a blinking amber error light--but the headphones still charge."
Also, the link you indicated to the sony manual about charging gives absolutely no information at all.
You are over thinking it, just try it
If you are really worried why not get a regular cell phone USB charger and use that, one that states like 500mA on it and has a female USB plug on it. That way you can use your headphone USB cable and plug it into the 5V 500mA phone 'charger'.
One last thing, just don't use Apple product 'chargers' to charge non Apple products, why you ask, because Apple does strange things with the pins on their 'chargers' in order to indicate the supply current. This can sometimes lead to adverse effects for non Apple devices.
Good luck.

zasy99 said:
E7ite: You should be fine, the fact that it charges via USB means that it must have its own internal charging circuitry.
I bet your Xperia tablet also charges via a USB type cable right, on a USB port?
All my USB 'chargers' have different mA rating yet they charge my products just fine as long as the mA rating is at LEAST what the device needs, not less, and hey, if its a little less it also works, just takes longer.
Look at it this way, the USB specs are always changing as is their current handling capability, now we are at USB 3.1, just recently we were at USB 3.0 which bumped up maximum device current usage during data transmission to 900mA or for dedicated charging 1.5A.
For USB 1.x - 2.0 it was 100mA before negotiation, up to 500mA thereafter, also with a dedicated charging capacity of 1.5A if the D- & D+ pins are shorted.
I bet Sony doesn't tell you that you can only charge via a USB 1.x - 2.0 port do they? Nope, that means if your computer has a USB 3 port that its has the potential to deliver more, remember, that's the key, it CAN deliver more if needed but it won't, it will only give the device what it draws.
The cable they supply with your headphone is most likely not a data cable but rather a so called charging cable so therefore is rated up to 1.5A or 1500mA but your headphones will only draw what they need to charge.
Everyone uses the term charger which is so wrong, when you put your AA or AAA batteries into the little black box and plug it into a wall, that is a charger, when you connect your car battery via the +/- terminals and clamps to the charger, that is also a real charger, they are directly responsible for charging the batteries.
All these other things we use to 'charge' our little electronic devices do nothing other than take the 120V A/C and convert it into for example 5V DC. The current rating they indicate next to the 5V is simply the max current handling capability, nothing more, it not what is pushed to the device, its what the device can request up to to be delivered. The actual charging goes on inside the device.
By the way, as the batteries charge the device reduces the current and sometimes also the voltage, batteries typically charge faster when they are low and able to absorb more current then as they fill up and can absorb less the charger adjusts to a more or less trickle such as 100mA or less in order to maintain but not overcharge the battery.
By the way, this is what I found on Amazon in about 2 minutes, a review from someone else who bought the headphones.
"For the price, sony should have included a wall charger. Instead they included a USB cable. The headphones will charge on any computer, but using a generic USB wall charger will show a blinking amber error light--but the headphones still charge."
Also, the link you indicated to the sony manual about charging gives absolutely no information at all.
You are over thinking it, just try it
If you are really worried why not get a regular cell phone USB charger and use that, one that states like 500mA on it and has a female USB plug on it. That way you can use your headphone USB cable and plug it into the 5V 500mA phone 'charger'.
One last thing, just don't use Apple product 'chargers' to charge non Apple products, why you ask, because Apple does strange things with the pins on their 'chargers' in order to indicate the supply current. This can sometimes lead to adverse effects for non Apple devices.
Good luck.
Click to expand...
Click to collapse
Thank you for reply.

[Q] Charger Question

So, I've been wondering this for a while and thought I just ask. I've read about stories where people bought 3rd party chargers and had their phone malfunction. Because of this I have been worried about using any other type of charger and stick with the stock. Would it be fine to charge my Nexus 5 which a more powerful charger. For example the Nexus 7 charger? There's also a few other 3rd party chargers which seem to be much more powerful, but I was just worried that it would cause problems for the phone. Thanks in advance!

I've got a ton of Chargers laying around and they all work just fine. As long as the charger output is 5 volts you should be okay.
Sent from my Nexus 5 using Tapatalk

0dBu said:
I've got a ton of Chargers laying around and they all work just fine. As long as the charger output is 5 volts you should be okay.
Sent from my Nexus 5 using Tapatalk
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Exactly 5 volts? The Nexus 7 charger is 5.2

PsychDrummer said:
Exactly 5 volts? The Nexus 7 charger is 5.2
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It should probably be fine. I used my Mom's Nook charger at her house the other day with no issues.
Sent from my Nexus 5 using Tapatalk

0dBu said:
It should probably be fine. I used my Mom's Nook charger at her house the other day with no issues.
Sent from my Nexus 5 using Tapatalk
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http://www.amazon.com/Anker-Dual-Po...5839252&sr=8-1&keywords=anker+usb+car+charger
So this one is apparently 18V...says should work though. Weird.

PsychDrummer said:
http://www.amazon.com/Anker-Dual-Po...5839252&sr=8-1&keywords=anker+usb+car+charger
So this one is apparently 18V...says should work though. Weird.
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Click to collapse
the charger that you linked to is 18 W (aka Watts), but it is still 5V. it has a max output of 3.6A (amp). Watts = Volts x Amps.
As long as it's 5V, you should be fine. using a charger with a higher max A rating won't change anything, how much current that is actually drawn (amps) depends on the device.

jss2 said:
the charger that you linked to is 18 W (aka Watts), but it is still 5V. it has a max output of 3.6A (amp). Watts = Volts x Amps.
As long as it's 5V, you should be fine. using a charger with a higher max A rating won't change anything, how much current that is actually drawn (amps) depends on the device.
Click to expand...
Click to collapse
Oh I see. Thanks!

Okay, quick electrical lesson.
Volts: This one is relatively fixed at 5 for all "USB-Powered" devices. However, virtually all electrical devices have a 10% allowable variance. So... anything from 4.5V to 5.5V should work just fine, and be considered "safe." Of course, this can be tricky since some less-than-trustworthy manufacturers (*cough*China*cough*) will include the 10% variance in the specs. So... a charger rated for 5.5V charger may actually be running at 5.8V, which is within the 10% variance for a 5.5V device, and since 5.5V is within the variance for the 5V spec, they'll just double-down, and stamp it with 5V, which is bad. Confused? Yeah, me too. Just stay away from those cheap eBay chargers, to avoid such shenanigans.
Amps (aka Current): The thing to remember here is that the draw is king. What I mean here is that the device drawing power is what's important. If your device draws 1A, then it will ALWAYS draw 1A, no matter if it's plugged into a 1A, 5A, or 1000A charger. However, it will also attempt to draw 1A if it's plugged into a 0.2A charger, which would obviously be very bad (well, unless you're TRYING to start a fire). USB devices are designed to draw 0.5A, since that's what USB 2.0 (on a computer) provides. However, many devices can draw more if plugged into a wall charger. So... you're almost always safe plugging into a computer, but your wall charger needs to be rated AT LEAST what the device expects. That can be hard to determine, so the rule of thumb is that whatever Amperage charger the device came with is the MINIMUM amperage charger you should use. However, there is no maximum, since draw is king, so go nuts in the other direction.
Watts (aka Power): Power = Voltage x Current, so Watts is nothing more than Voltage times Amperage. Thus, a 5V charger charging at 2A is 10W (5x2=10). Now that you know this, you can ignore it. Nobody but the electric company cares how many Watts your wall charger is pushing. The only, and I mean only, thing this is good for is determining the Amperage if the manufacturer doesn't provide it. So... if the only spec listed for your micro-USB charger is 12W, then you can figure out the amperage by dividing that by 5 (since all USB devices are 5V). Your 12W charger, therefore, is pushing 2.2A. See the section on Amps, since that's what's really important.

jt3 said:
Okay, quick electrical lesson.
Volts: This one is relatively fixed at 5 for all "USB-Powered" devices. However, virtually all electrical devices have a 10% allowable variance. So... anything from 4.5V to 5.5V should work just fine, and be considered "safe." Of course, this can be tricky since some less-than-trustworthy manufacturers (*cough*China*cough*) will include the 10% variance in the specs. So... a charger rated for 5.5V charger may actually be running at 5.8V, which is within the 10% variance for a 5.5V device, and since 5.5V is within the variance for the 5V spec, they'll just double-down, and stamp it with 5V, which is bad. Confused? Yeah, me too. Just stay away from those cheap eBay chargers, to avoid such shenanigans.
Amps (aka Current): The thing to remember here is that the draw is king. What I mean here is that the device drawing power is what's important. If your device draws 1A, then it will ALWAYS draw 1A, no matter if it's plugged into a 1A, 5A, or 1000A charger. However, it will also attempt to draw 1A if it's plugged into a 0.2A charger, which would obviously be very bad (well, unless you're TRYING to start a fire). USB devices are designed to draw 0.5A, since that's what USB 2.0 (on a computer) provides. However, many devices can draw more if plugged into a wall charger. So... you're almost always safe plugging into a computer, but your wall charger needs to be rated AT LEAST what the device expects. That can be hard to determine, so the rule of thumb is that whatever Amperage charger the device came with is the MINIMUM amperage charger you should use. However, there is no maximum, since draw is king, so go nuts in the other direction.
Watts (aka Power): Power = Voltage x Current, so Watts is nothing more than Voltage times Amperage. Thus, a 5V charger charging at 2A is 10W (5x2=10). Now that you know this, you can ignore it. Nobody but the electric company cares how many Watts your wall charger is pushing. The only, and I mean only, thing this is good for is determining the Amperage if the manufacturer doesn't provide it. So... if the only spec listed for your micro-USB charger is 12W, then you can figure out the amperage by dividing that by 5 (since all USB devices are 5V). Your 12W charger, therefore, is pushing 2.2A. See the section on Amps, since that's what's really important.
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Click to collapse
I've plugged my device into chargers before that have rated outputs of .5A-1A when the device "expects" more... so, why didn't it start a fire?

Nitemare3219 said:
I've plugged my device into chargers before that have rated outputs of .5A-1A when the device "expects" more... so, why didn't it start a fire?
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How much "more" are you talking about?

طوني تبولة said:
How much "more" are you talking about?
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The stock charger is 1.2A, correct? So given that much... a charger I have used a few times on my Nexus 4 and 5 at a friend's place only outputs .5A... so at least .7A from what our phones should be able to draw.

Nitemare3219 said:
The stock charger is 1.2A, correct? So given that much... a charger I have used a few times on my Nexus 4 and 5 at a friend's place only outputs .5A... so at least .7A from what our phones should be able to draw.
Click to expand...
Click to collapse
An Android device knows that it's plugged into a wall charger, and thus can use more than 0.5A, only if the data pins are shorted together. Otherwise, it will assume it's plugged into a computer and only use 0.5A. Chargers made for android devices are usually so equipped. Apple chargers and some cheap-o chargers aren't. That's one reason why you'll see chargers with nothing more than a USB slot (no cable) specify that they're only compatible with Apple devices. Technically, they're compatible with any USB device, but not at the high charge rate.
Having said that, manufacturers can build in some safeguards. Quality chargers simply won't output more current than they're designed for. How they go about this varies. They may limit the output to their rated specs, they may blow an external breaker, or they may blow an internal fuse (usually killing the charger forever). Cheap chargers may not have such safeguards. Plus, many (if not most) phones/tablets will recognize when they're hooked up to a low-current source, and automatically switch to the low charge rate mode (0.5A).
In short, quality equipment is usually designed to be safe, with safeguards to protect against common scenarios. It's the cheap chargers that you have to worry about, because they tend to cut corners to keep the cost down. Safety provisions aren't technically necessary, and are usually the first to go.