Technology Explained

Why Can’t I Charge All Gadgets With the Same Charger?

Ryan Dube 19-06-2013

Years ago, at my previous job, my boss came into the office and asked a group of us if we had a spare cellphone charger. As everyone scrambled to help the boss out by offering their own cellphone charger, I pondered for a moment how odd it was that no one was bothering to ask him what model of phone he was using.


I was deep in the middle of a project, so didn’t pay too much attention to what was going on, but I do recall seeing my boss take the charger that one guy handed to him, compare the connector with the port on his phone, and satisfied, took the charger into his office.

About ten minutes later, the boss came back into our office area and sheepishly informed us that the charger had completely fried his phone. “I forgot to check the voltage of the charger” was his explanation.

Up until a few years ago, the mish-mosh of assorted chargers and connectors led to this problem more often than people realize. The general assumption by many people was that if the connector fit perfectly into the phone’s power jack, then it should be sufficient to charge the phone. This wasn’t the case at all. In the best of cases, the charger simply wouldn’t do anything. In the worst, it would fry the phone’s circuits and damage it permanently.

Thanks to the advent of USB, that all changed. However, there are still some important things you should keep in mind when you’re looking for a quick, temporary charger to get your phone or tablet’s battery charge back up.

Not All Chargers Are Created Equal

Here at MakeUseOf, we’ve tried to help out readers with a number of charger issues through the years. Matt provided 5 ways you can charge your phone in an emergency 5 Ways To Charge Your Phone In An Emergency Smartphones can be important tools in an emergency. Besides providing the chance to call for help, a phone can act as a flashlight, compass and GPS. But all of a phone’s functions rely on the... Read More , and he also described how wireless charging works What Is Wireless Charging & How Exactly Does It Work? [MakeUseOf Explains] We live in a wireless world. Except we don’t. Sure, we can send huge amounts of information across the airwaves, but the devices capable of sending and receiving it are tied down to power cords.... Read More . Christian provided a few tips on how to troubleshoot when your HP TouchPad isn’t charging HP TouchPad Not Charging? Don't Worry, It's Probably Not Bricked! The HP TouchPad is a remarkable piece of kit. This tablet computer with its dual core CPU was released with a buggy version of the webOS operating system back in mid-2011 and failed to capture... Read More . There are a lot of times when it would be good to understand just exactly how charging actually works.


So, just as a quick exercise, let’s do a quick test. Go around your house and collect as many of those newer style USB chargers that you might have. Some might be some form of mini-USB, or you might have those USB chargers for your tablet. Maybe you have a few of those “smart chargers” that you can disconnect the cord from and insert other USB cords into it. Gather those all up and then bring them back here.

Now, before I have you look at the actual numbers on these things, I’m going to describe what we’re looking at. Years ago, there was a much larger variety of chargers that went along with Nokia, Motorola and all other brands of phones. Everyone had their own proprietary connector that you had to purchase special if you ever wanted to replace it. Hopefully, you had a phone that was common enough that you could find the charger in a regular big-box store.

charge multiple gadgets

Each one of these had its own voltage and current rating, based on the phone manufacturer’s specs. USB changed everything, because manufacturers finally standardized on two or three mini-USB jacks, as well as the typical 30 pin tablet heads.


Those newer USB chargers all carry a standard output voltage spec of 5V. This is great, because now no one should be able to plug in a phone with a lower voltage demand and fry the phone, because the phone – if it’s newer – is likely manufactured based on that 5V input voltage.  However, not all is right with the world just yet. Every device has its own special current demands – so the current ratings for many of the manufacturer chargers still varies.

To show why this matters, take a look at the diagram below.

how chargers work

These aren’t your standard electrical symbols. I’ve taken the liberty of creating my own symbols to make visualizing what’s going on a little easier. Picture the “Amps” circle as a sort of a power generator that only works as hard as it has to in order to provide the amount of “energy” that your device needs at any given moment. Picture the “Volts” as a constant waterfall of energy that never changes.  Now, let’s take a look at those chargers you’ve collected.


Take a look at the labels on them and look for the “OUTPUT” section. Log the different numbers you see. Here are three chargers that I collected from around my house:

Samsung – 5 Volts, 0.7 Amps
Motorola – 5.1 Volts, 0.850 Amps
Asus – 5 Volts, 2 Amps

As you can see, with modern chargers, the waterfall never changes, but the capacity of each engine is different. Some chargers can only put out 0.5 amps. Others can put out 2 amps or more.

In the old style chargers where you might accidentally plug a charger rated with a large voltage into a phone with a small voltage requirement, it would be like trying to shove way too much energy through a very small hole.


how chargers work

That mass of energy would blow apart the hole – basically overcharge the circuit and fry it. Now that everything is based on 5V, what’s the problem? Why can’t we now swap around power chargers? Well, if you’ve ever tried plugging in a larger smartphone with a USB charger from a smaller phone, you probably know that the smartphone won’t work if you try to use it while charging. This is because that smaller 0.7 Amp charger just doesn’t have an “Amp” engine powerful enough to provide the energy needed by a 1.2 amp device in full use.

However, you could definitely take the 2 Amp charger for the larger device and use it for a smaller device that only needs 0.7 Amps, because that larger charger has an engine that’s powerful enough to feed all of the needs of that device.

how chargers work

This is the main difference between voltage and current in chargers. When that rating label shows a voltage that’s higher than the phone’s rating, it’s going to provide that voltage no matter what – and you’re going to destroy the device. However, when that rating shows an amperage that higher than the phone’s rating, nothing is going to go wrong. This is because the device “draws out” the amps from the charger that it needs – the charger will not pump the maximum rated amperage into that phone.

So, as long as your tablet charger is rated with the same voltage as your smartphone (these days, that’ll be 5 volts), then go ahead and charge your smartphone with it.

charge multiple gadgets

Keep in mind that the cable matters too. That USB cables that came with your phone may plug into your tablet’s interchangeable charger, but that USB cable will limit the current to between 1 and 1.5 amps.  Meaning – if you try to use your phone’s USB cable to charge your tablet or large smartphone, it may not work. Especially if you’re doing something with the smartphone that forces it to require a greater current draw.

Another mistake people make – assuming anything can be plugged into the computer USB port and charge. The reality is that a standard USB on a laptop is approximately 0.5 amps max. So, many devices will actually use up the same (or more) charge than the USB port can supply, never charging the battery at all.

The world of electric power can be a little complicated. The relationship between current and voltage isn’t always obvious, and sometimes people get tripped up when using certain chargers that have no business being plugged into those larger electronic devices. Hopefully this explanation provided you with a better understanding of what to look for when you’re trying to match up that charger with a device, or at least now you have a way to try and troubleshoot problems.

Have you ever had any odd charger issues? Every fry a device by plugging in charger that was too large? Share your thoughts and experiences in the comments section below!

Image Credits: Burning Cellphone Via Shutterstock, Power Up Via Shutterstock, Smart Phone Via Shutterstock

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  1. Filip
    April 7, 2019 at 10:03 pm

    Very good, thank you.

  2. Jong fernandez
    November 1, 2017 at 12:09 am

    Thank u sir for ur advises, but i read also that now even u will charge ur fon to 12v or 24v, the fon will not charge and not fry because of its built in controller.

  3. anon
    August 26, 2017 at 10:48 am

    thank you for the great article! I have an lg g3 and it basically only charges with a few things and its really annoying and I wasn't understanding why. If a cable does not say output but says vw-1 and 30v is it the 1 volt its charging at? Also the article say

    "Another mistake people make – assuming anything can be plugged into the computer USB port and charge. The reality is that a standard USB on a laptop is approximately 0.5 amps max. So, many devices will actually use up the same (or more) charge than the USB port can supply, never charging the battery at all."

    I didn't quite understand this. Will the phone only not be able to charge if its on? Like if you turn the phone off can it manage to slowly charge? I plug my phone into a usb on laptop or desktop or a usb in my car and it wont charge even if the phone is off. Should it be able to charge the phone if the phone is off just very slowly? I run into the problem you mention where it detects charging on and off and it will not charge or die lol just wondered if my cell phone will always need a charger which sucks for in the car were there is an easy accessible usb I had hoped could charge my phone but doesn't seem to work. Thank you!!

    • anon
      August 26, 2017 at 10:59 am

      edit** sorry it doesn't detect on and off if just says charging but doesn't ever charge to break even or slowly drains even while "charging"

    • anon
      August 26, 2017 at 11:17 am

      Side note: for example I just got a brand new Lenovo thinkpad and it was having the same problem and not being able charge the phone for about 15 mins and the phone would just die and now miraculously it has managed to start working and has half battery charge on phone. will charging my phone using the usb on my laptop possibly damage the computers usb in any way? if so id rather not use the computer to charge it. thanks again.

  4. Lisa Farson
    May 6, 2017 at 10:05 pm

    Thank you, 100 times over, for taking a topic which is too lofty for me to grasp and making it understandable. I will start looking now for anything else you've explained since I have just found, after a long history of looking, someone who can help me assimilate some technical concepts. Bravo!

  5. Anonymous
    January 9, 2016 at 1:35 pm

    simply explained , thanks Ryan :)

  6. Eissa Ibrahim
    January 9, 2016 at 10:06 am

    Very helpful and simply explained , thank you Ryan :)

  7. Anonymous
    October 13, 2015 at 12:08 am

    All actual "CHARGING CORDS" were created equal. The power source of said charger is the only this of importance.

    • Anonymous
      October 13, 2015 at 12:10 am

      *thing. Or "of the two."

  8. Anonymous
    September 29, 2015 at 3:31 pm

    My original Huawei was of 5V and 1A. Now I bought an adapter of 5V and 2A. Is it good? or it will blow my battery?

  9. Anonymous
    August 9, 2015 at 8:02 pm

    I've got a HTC charger for my HTC phone but usb got lost so can I use same adapter with some other usb

    • Anonymous
      September 21, 2015 at 8:35 am

      Sure you can , coz USB is universal that of the adapter. so you can buy another USB and use it for the same adapter the result will be same.

  10. george
    February 14, 2015 at 5:05 pm

    Baterry university... Com. Valuable info

  11. Big Chris
    December 30, 2014 at 8:21 am

    There's a great little device available (e-bay/amazon etc) called 'charger doctor' for a few dollars/pounds. It plugs into a USB socket and has its own USB socket into which you can plug your charger cable. It then shows the voltage and current flowing through it. I've tested all my chargers, both wall plugged and car cigarette lighter type, as well as computer/laptop USB ports and portable 'power pack' type chargers, with a variety of cables. The variation was quite surprising and I ended up throwing out many items. Worth getting one a experimenting yourselves. I'm not sure of the accuracy of the displayed voltage/current at such a low price but as a device for making comparisons it seems pretty reasonable.

  12. Silas
    December 20, 2014 at 4:06 pm

    Li-Ion batteries don't not suffer from the old Ni-Cad memory effect. In fact, Li-Ion batteries prefer to be kept topped up if possible. If I'm near a charger, my phone goes on the charger... and I get amazing longevity out of my Li-Ion batteries.

  13. Jack
    June 28, 2013 at 9:29 pm

    That was a really good article. It answered a lot of questions I have had about all these different chargers for a long time. Now I know what I can and cannot use.

  14. null
    June 26, 2013 at 1:37 am

    Is there an article like this on Laptop chargers? At one point with five people in the household each with a laptop..things got screwy. I often look at our chargers wonderin which came with which (the part that disconnectsp and is plugged into the wall) because my kids would just unplug from the bar, leave that part plug in the wall where they were and grab a similar one and go elsewhere...i have NO IDEA what came with what and i have no idea what the numbers mean alth i have tried to look them up.

    • Charlie O.
      June 27, 2013 at 6:11 am

      Well, if you get the chance, use a cheap magnifying glass and read the specs on each charger and laptop. Make a list with the names of the owners as your heading. The first thing to look for is the manufacturer's name. In the unlikely event that you have five completely different laptops, just match up the manufacturers and Bob's your uncle. Then I would get beige masking tape, put a large, flag like piece on each charger, near the end that plugs into the laptop, and write something stupefyingly obvious on it (like "MOM" or "Dell" or "Mac Book Air", or whatever. Just make it unique to the household). On the chargers, you want to look at the line that says "output" and then it will list volts (ex: 19.5 V) and amps (ex: 3.4 A). Those are the actual specs for my Dell laptop. Then, on a tag under the laptop is a line that says "Input". On mine, it says "19.5 V 3.4A / 4.6A / 6.7A". That's Dell's way of saying that several chargers will work with this unit, three different Amp ratings but they all have to be 19.5 Volts. If you manage to get a list that uniquely detects a separate charger for each laptop, get the tape out, mark em' (put a corresponding piece of marked tape on the matching laptop) and you're done. If not, as a last resort, check the DC power jack sizes (the round end that plugs into the laptop) and look for incompatibility. If, for example, you had two on the list that either had the same info, or not enough info listed to tell, a power jack that only fits one and not the other is as good a way as any to get that list functional - grab the tape. Also, consider that if it walks like a duck.... you may have a pair or more of off brand units that use, essentially, universal power supplies (generic) so, again, if the power requirements are equal (and ONLY if you're sure you read them right and ONLY if they're ACTUALLY listed) then it doesn't really matter and you can mark the matching units accordingly, remembering to mark them separate from the previously ID'd units that are different from the generic ones.

      Also, if I take your meaning correctly, and that by 'bar' you mean the block on the power supply, and not a wall plugged-in 'power strip' where you plug all kinds of stuff into, then what you're saying is that the detachable, AC cord with the universal, three prong insert for the 'bar' that plugs into the wall is being swapped out by the others in the house - and don't sweat it. It's only supplying the 'bar' with the same AC it gets from the wall. Those actually are universal - as long as it fits properly into the device you're powering. HOWEVER, leaving it plugged in to the wall without having it plugged into a device may present an electrical issue (Electrical Issue means FIRE HAZARD) Lovingly smile at your children and inform them that if they burn the house down they will NOT get new laptops with the insurance money. Then give them one of those free twisty-ties you get at the produce or bulk section of the super market and remind them that saving a few calories per day by not carrying the power cord with them will, in no way at all, save the ozone layer, prevent global warming, cure acne or help them get their licences. It will be equally useless against the Ninjas that are sure to stop by later because, "If you don't have it with you, you can't kill ninja's with it." (personal credo)

    • Charlie O.
      June 27, 2013 at 6:13 am

      Jackson, if you got your ears on, now would be a great time to allow us to post pics.

  15. null
    June 26, 2013 at 1:22 am

    Thank u soooo much for this article! my mom has messed up so many phones and tablets just sticking anythung in. Im emailing her this article!

  16. Krzysztof Buzko
    June 25, 2013 at 6:04 pm

    Thanks for the article, now I understand difference between amps and volts ;)

  17. Stephanie Staker
    June 23, 2013 at 5:01 am

    Thank you for this info. Fortunately, I have a hubby who knows electronics so this even made sense to me! A lot of times, technical stuff doesn't.

  18. Doc
    June 21, 2013 at 6:05 pm

    "typical 30 pin tablet heads." AFAIK, the only "standard" 30-pin connector was the original Apple 30-pin dock connector (yes, several cameras and other devices may have had other 30-pin connectors).

    The EU solved the problem nicely by requiring cell phone makers to standardize on 5v micro-USB (which also have a 10x longer connect/disconnect lifespan than mini-USB). Even Apple has to provide 30-pin or Lightning-to-micro-USB adapters in the EU.

  19. Sharon V
    June 21, 2013 at 2:29 pm

    I guess I should correct my statement above. The phone did charge for a while but I only had service 28% of the time. So it did not work well - I think it was a combination of a defective phone and an ineffective service provider, however it had nothing to do with the charger.

  20. Sharon V
    June 21, 2013 at 2:27 pm

    I had a Samsung Galaxy 2 that was charging fine with a charger and suddenly it stopped. I went to my phone company store and they told me it was that the charger was not compatible - even though it had been working so they sold me an expensive charger they had. It still didn't charge it was the phone - That phone was a total dud for me never would charge never had service and the phone company wouldn't fix so I had to change companies - so don't always jump to the conclusion that it is the charger some times it's the phone and some times the connectors on the phone get dirty as well. You used to be able to clean most connectors but now it is difficult to do that.

  21. Karl
    June 21, 2013 at 12:46 pm

    I remember blowing a few transformers while plugged into games consoles... the console drew more amperage than the bricks were rated for

  22. Joan Advincula
    June 21, 2013 at 5:37 am

    My phone got fried by the charger it came with. How does that happen?

    • digital_addict
      June 26, 2013 at 9:58 pm

      Faulty phone or charger. I have a power supply capable of delivering 5 volts at 30 amps and it's never fried anything.

  23. Alan Trinder
    June 21, 2013 at 5:29 am

    Good read, I recall a move to standardise phone power connectors years ago, must have been signed in invisible ink...

  24. digital_addict
    June 20, 2013 at 10:58 pm

    Beware of the wall wart usb chargers that have a minimum current draw requirement.
    I have a plug (1amp) that does not switch on unless it has a current draw (battery resistance) of more than 160ma. This is fine for charging a Kindle, or running a Raspberry Pi, or even a 12amp battery bank, but it will not charge an iphone 4, The iphone must not require more than 160ma or the data pins in the usb plug may need shorting. I can't find the charging requirement for my apple phone, it must be an apple secret. No change there then.

    • null
      June 26, 2013 at 2:06 am

      how do you know what the min draw req is?

      • digital_addict
        June 26, 2013 at 9:53 pm

        You ask the supplier, if he can't give an answer then don't buy.

  25. Jim
    June 20, 2013 at 10:39 pm

    If your device battery hss run excessivly low, you may need a heavier chsrger to kickstsrt the charging process. Many supplied chargers do not have the capacity to start charging a severly discharged battery.

  26. Steve J
    June 20, 2013 at 10:25 pm

    I thought the US was developing/mandating standardization is this area similar to the EU. I remember when Martha Stewart (of all people) testified before congress with her box full of phone chargers. This was a few years ago now. I thought the 'new standard' was supposed kick in about now. But knowing the way the US government works, we'll probably have to wait another decade or so...

  27. BB
    June 20, 2013 at 8:16 pm

    Nice article, thanks! In it you mention:

    "Keep in mind that the cable matters too. That USB cables that came with your phone may plug into your tablet’s interchangeable charger, but that USB cable will limit the current to between 1 and 1.5 amps."

    That seems to imply that some USB cables are different from others - is this the case?


    • Charlie O.
      June 20, 2013 at 11:48 pm

      Ooo, Ooo. I can answer that.

      Just like the limitations on a machine (like your car as a towing machine) can have a listed rating (my truck's bumper says "3000 lb trailer weight"), the various parts that assist in the weakest area of that limitation may vary. With a car, it could be the transmission, the suspension or the strength of the actual bumper. With a cable, the diameter of the wires and the amount of insulation on them determine factors like heat, electro-magnetic field effect, and of course, electron flow. But really, the options here are somewhat negligible. If the cable is rated at less amps than the charger is capable of putting out, its a design issue and your charger is junk. If the cable is rated at higher, it's not a problem.

      I think the most likely situation where this could be an issue is using a cable from a modular charger, where the cable is separate from the part that plugs into the wall. Here, if your cable is from a charger rated LESS than the charger and device your charging, your putting more amps through the cable than it was designed for. Neither the charger nor the phone can detect the limitations of the cable. Here there are two possible outcomes, either or both likely - less available amps for the device and heat buildup in the cable. I don't like either of those so I would try to keep the cable matched to the device it came with or, if you need to buy ONLY a USB power supply cable, buy it from a set that comes with a charger rated at or better than the amps listed on your device. Yes, now you have a more powerful charger, but you may not need another car charger or wall charger and you may want to keep the power supplier (the part that plugs into the wall or car) as OEM.

      • BB
        June 21, 2013 at 8:58 am

        Thanks Charlie, good reply. I did search on eBay, and on various other places, to get a good spectrum of what sort of USB cables are available. There were only one or two that made any sort of reference to the current carrying capacity of the cable. Perhaps this is a new niche that some cable supplier can exploit... I have a selection of cables at home (I find that, with teenagers in the house, the best way to ensure cable availability is to saturate the house with them ;-). I'll investigate further to see if there's any noticeable difference, though this won't be trivial without a standardised test setup.

        Anyway, if I find anything, I'll post it here.

  28. jkoenig24
    June 20, 2013 at 7:43 pm

    You forgot to explain the "Magic Smoke" that actually powers electrical / electronic devices. Most people have, at one time or another, witnessed the puff of this Magic Smoke leaving a device. Once the Magic Smoke is gone, the device stops working. Apparently, no one has figured out a way to reinstall more Magic Smoke so their devices can be used again ;)

    • Charlie O.
      June 20, 2013 at 9:00 pm


      I remember them packing LOTS of that magic smoke into the old 'tube' televisions and stereo sets. They must be making a more efficient version of the smoke, 'cause I don't see so much of it these days.

    • null
      June 21, 2013 at 1:29 pm

      Unless you have an older British-made car with Lucas electrics....

  29. Lisa Santika Onggrid
    June 20, 2013 at 6:43 pm

    Thank you for the explanation. It clears up a few things I were confused of.

  30. Jack Shaw
    June 20, 2013 at 5:49 pm

    Thanks for the info. But, I am having a great deal of difficulty reading the voltage/amperage information on any of the chargers I have. Documentation with the devices doesn't cover the chargers. A search on the web doesn't help either. I have a number of different devices and chargers and would like to reduce that two only what I really need to carry on trips. Is there somewhere I can gather this information?

    • Ryan Dube
      June 20, 2013 at 7:45 pm

      Jack - it's nearly always listed on the charger in very, very small print, next to "OUTPUT". It'll show voltage, current, and sometimes overall power as well, in Wattage.

      • Jack Shaw
        June 20, 2013 at 8:15 pm

        Even with a magnifying glass and bright light it's almost impossible to read either samsung or motorola.

  31. RL Jenkins
    June 20, 2013 at 5:28 pm

    I remember using a 3/8 hose to water my garden. It tookforever because the volume of water was so low. After I went and bought a 5/8 hose, it took a fraction of time. The current is much the same way. A too low of current can mean a battery never topping off or just take longer to charge.

    • Ryan Dube
      June 20, 2013 at 7:44 pm

      That's a great analogy.

  32. dusters16
    June 20, 2013 at 5:23 pm

    I have a question. so i have an old Motorola Droid 1 and Droid 2. I also have a HTC Evo 4g and a Evo Shift 4g. they all use micro USB, but when i use the htc cables on the Droids, they either don't charge or have some crazy screen issues. they would be ghost pressing and it seems to just go crazy, opening apps, calling people, playing games. the moto micro USB cable obviously works prefect. when i used the same htc cable on the htc's, they work prefect. the moto cable on the htc's work prefect too. anyone know why the droids are picky when it comes to cables? they were all plugged into the same wall wort, and the same usb port on a laptop .

    • Ryan Dube
      June 20, 2013 at 7:34 pm

      dusters16 - what are the voltage/current ratings for the HTC charges? You can look up the voltage/current requirements for Droid 1 and Droid 2 - I suspect the HTC chargers aren't quite right considering the behaviors your describing.

  33. Bud
    June 20, 2013 at 4:58 pm

    My concerns are with regular alkaline AA/AAA batteries and NiMH battery chargers, as WARNING labels mention the possibilities off over-charging and causing batteries to explode....... ???

    • RL Jenkins
      June 20, 2013 at 5:37 pm

      Many chargers are designed to detect when the battery is fully charged. Putting the wrong battery in a charger can cause the battery to overcharge. With cellphones; the circuitry that determines when the battery is charged is built in the phone not the charger. This is why generic chargers can charge a phone and you later see a notification the phone is fully charged.

    • dragonmouth
      June 20, 2013 at 6:30 pm

      You should NEVER try to charge alkaline batteries. They are not designed to be re-charged. Once they are discharged, they should be disposed of properly.

      NiMH batteries will not explode from overcharging. The may explode if you heat them to 200-300 degrees. Can't tell you for certain since I never tried to do it.

  34. Daniel Voyles
    June 20, 2013 at 4:35 pm

    Since the flow of electrons doesn't change from the output of your USB charger, doesn't the excess which the charging circuit does not use have to escape somehow? Like through heat? Would this not eventually damage the components of the charging circuit in your phone?

    • Ryan Dube
      June 20, 2013 at 7:44 pm

      No - it isn't like a fire hose where you're trying to shove 0.8 amps into something that only needs 0.3. You have to think of current differently, it's not like voltage. Current is like an all-you-can eat buffet for a phone that has requirements less than what's available by the charger. However, if you're a phone that needs 0.8 Amps and the charger is only 0.3 Amps, it's like a football player going to a salad buffet. The dude is not going to get enough calories and will probably starve. :-)

      Sorry - that's the best analogy I can come up with. Maybe someone out there can be a bit more creative. :-)

      • my10sense
        June 20, 2013 at 8:20 pm

        Boy, do I hate analogies. If he ate enough salad, he would get enough calories. Similarly, eventually, the lower current charger should charge up the battery--as long as it was current limited. If it isn't, it's going to heat up and either shut down or fry, depending on how sophisticated (protected) it is. I once had a Verizon tech explain to my wife and me that we should turn off the phone when charging just like we wouldn't charge our car battery with the car running. An (obviously more) useful comparison here would be a trickle charger--you can't start a car with it, but eventually it gets the battery charged.

        • Charlie O.
          June 22, 2013 at 9:07 pm

          I'm glad you mentioned current limiters. I also mentioned overvolt circuitry; people need to know that there are many different standards in micro-circuitry for these things, depending on where they're made and by whome. Also, there's no standard dictating that any of these specs have to divulged on the product or the packaging and even if they were (maybe online) available, the specs get complicated - but more than that: what would you be matching those specs against??!? The safest solution is to go with a known, trusted manufacturer whose reputation is more important to them than saving half a mil over the next quarter.

          Also, electricity works in a state that is easily quantified, but the real limits of the parts (the devices AND/OR the components that make up those devices) are (unlike electricity) subject to the incidental tolerances inherent to the manufacturing process. That and the fact that component failure is (like drug interaction) only looked at in a shallow, superficial way, there's no way to predict if a failure will result in 1) your charger not charging, or 2) your charger turning into an arc-welder (exaggeration). I do know that companies with more to protect will look at the problem more comprehensively, they guard their data and they charge us for its employment. Reputation is not everything, but it's a lot.

    • Charlie O.
      June 20, 2013 at 10:20 pm

      Let me know if this helps: You have a hose. It has a diameter and a pressure. You want to put various 'devices' on the end, lets say: a pressure washer (machine), a garden sprayer and a water balloon filler. No matter what, you have a couple of limits here: 1 the diameter can be changed in the device, but the hose itself stays the same, 2 the pressure is the pressure at the hose output (the hose end). It stays the same at that point.

      A quick disclaimer: electronics instructors have been using the water analogy for decades and sooner or later, that analogy breaks down, but for our purposes, it may serve.

      The water balloon filler will reduce the diameter at the output, but the pressure behind it stays the same (which is why a perception of increased pressure exists - same pressure in a smaller cross section or impact area). So you have reduced flow, but not pressure. Here the pressure is like the Voltage - it stays the same, but the flow is like the Amperage, the device 'needs' less and true to form, you have less output. (Fill two buckets side by side with an open hose vs a H2O balloon filler and guess which will be filled first) (Spoiler = open hose, try it.) So, here the volume or diameter of the flow (amps) is 'available', but not being used.

      The garden sprayer has a twistie end for 'variable' output. And notice on some models, there's a threaded end that fits another standard fitting. If you attach another hose to that fitting and change the allowed amount of water to be the maximum (assuming the max in the sprayer = the max of the hose), then the other hose (the one we screwed onto the output end of the sprayer) would have the exact same output (diameter, pressure, flow) as the supply hose. As you close off the valve though, you're reducing available water - even though it's at the same pressure as it exits the restricting valve - and then asking it to fill the same void in the form of the second hose. The exit pressure at the valve is the same as the entrance pressure into the sprayer, BUT the exit pressure of the second hose is reduced because the 'need' is higher than the supply (the amount of, say liters per second vs the diameter or volume of the second hose). Here we have again reduced the 'need', but attached our output to a device with more need, so it'll take longer to fill. This equates to a lower amperage rated device supplying a higher rated battery. Notice that, like the analogy, it takes longer to fill but, unlike the analogy, there's no accounting for damage to the equipment due to mismatched tolerances. Just remember that in electricity, within a certain percentage of amps, over is ok - under takes longer. Hang in there.

      Now for the pressure washer. Here we are going to ignore the intended output since it equates for other discussions I've had, but not this one. The important thing to remember is that the machine needs lots of water to work, so it has a tank. The comparison here is between the machine's tank and the water balloon. If you leave both attached to their respective, aforementioned 'devices' indefinitely, the tank will hold but the balloon will burst. Now, the analogy will break down further upon scrutiny, especially by a plumber, but keep in mind that we said that pressure was voltage. The pressure will kill the balloon. The voltage will kill the phone (or whatever). The pressure will NOT kill the tank in the machine because it's rated for that pressure. I'm sure if you could get more pressure, you could kill that too. That's voltage. The diameter, or flow in units per time (amperage) simply says how long it's going to take.

      How'd I do? Happy to specify or elaborate. All comers welcome. Please be gentle and remember the disclaimer.

      • Daniel Voyles
        June 21, 2013 at 3:31 pm

        The electrical engineer I work with told me that it is like going to a fire hydrant and hooking up a garden hose. You will get the same pressure (voltage), but your flow (amperage) will be less. Although it would take much longer to fill a swimming pool with a garden house compared to a fire hose. There are differing variables between this analogy and that of a phone with a calibrated charging circuit. The pool would overflow while a charging circuit would turn off the flow or reduce the flow when the battery is full.

        • Charlie O.
          June 22, 2013 at 9:20 pm

          YEA!! Confirmation on my attempt. Imagine your fire hose hooked up to my pressure washer! You're right about the pool, but another way to think about it would be like having a shutoff valve attached to the filler mechanism that is triggered by the height of the water (like a toilet tank).

          But you're also right about the differing variables: if the pressure of the neighborhood water supply suddenly doubled, it's not likely that the valve would melt open ('shorting' out the system) causing the pool to fill up so fast that it would explode.

    • Doc
      June 21, 2013 at 6:22 pm

      To expand on Ryan's comment, no, plugging in something that requires 0.3 amps doesn't permit the wall outlet to send 5.0 amps to the device, just like plugging in a 40 watt desk lamp doesn't pull as much power as plugging in your big-screen TV, and a hair dryer pulls even more; otherwise, your house's circuit breakers would trip every time you plugged *anything* into the wall.
      Most residential circuit breakers are 10, 15 or 20 amps (1,100, 1,650, or 2,200 watts total draw before they're required to trip), but your cellphone (and everything else) draws a *lot* less than the *maximum* current, so you can have 4-5 outlets on one circuit breaker, and everything plugged in draws a portion of that.

  35. EYE BM (@EYEBM)
    June 20, 2013 at 4:31 pm

    Because the companies want to charge you extra for their own charges, that's why. and that's the ONLY reason why. Same charger, different end.

    • null
      June 21, 2013 at 1:39 pm

      I wonder how much that was Barnes & Noble's thinking when they made the charging cables for the Nook Tablet. The cable end *LOOKS* like one of the less-used USB connectors, and another charger with that end will *sort of* charge it, but in order to get a charge that completes some time in this century, you have to use a Nook-specific cable, which is about 1/16-1/8" longer. And there are some wall USB adapters that won't put out enough power to charge the tablet.

      And finally, to put a final insult on it, the B&N proprietary cables are built *SO* poorly they can break within a couple months. And just *try* to find a replacement for just the cable, taht doesn't require you buying yet another wall-wart piece.

  36. Totoliciu Dan Catalin
    June 20, 2013 at 4:12 pm


  37. Onaje Asheber
    June 20, 2013 at 3:47 pm

    Will needed info, Ryan!

  38. Mike
    June 20, 2013 at 3:44 pm

    Thanks for the information. I bought spare battery power supplies for charging when in the wilderness and found the same sort of problems. Even if it plugs into your device that does not mean it will juice it up. Also the sales people gave me wrong information.

    Another irritation I would like to scratch: The one standard I wish they would make all manufacturers comply with is a label on the charger that will tell you what device it connects with. If I remember I usually stick a label on each cord but why can't the manufacturers.

    • Ryan Dube
      June 20, 2013 at 7:41 pm

      Mike - I made the same mistake re: the battery chargers. I completely forgot to check that the current capability of the battery pack/charger was sufficient for the phone. I found that my phone started charging okay, but then the charging icon changed to a strange one, and the charge started dropping. Very annoying. I'm back to searching for a stronger battery pack that can supply the required juice.

      • Charlie O.
        June 20, 2013 at 9:28 pm

        This brings me to the point I was thinking of while reading your article, Ryan. Under-current can be equally problematic, but over the long term. As you know, all batteries have a certain memory (from the old days of Ni-Cad) or, more accurately, elasticity. Under powering the charge will almost certainly affect the battery's behavior.

        In almost every instance where the amperage is not what the battery considers 'optimum' (regardless of the manufacturer's posted specs), the charge time AND number of recharges will be reduced - and I can't think of any instance where the change would be for the better. The only way to account for it would be to have the device keep track of as many factors as possible for each charge, but a key factor which I see no evidence of in terms of data availability, would be voltage and amperage. If smart devices could track charge state over time / per voltage and amperage availability, you could write software (theoretically) that could optimize charging, or at least make suggestions (I like that charger better than the other one).

        ALSO EVERYONE ! - be ware of voltage differences in cheap, aftermarket devices. I have seen outputs on chargers listed as 5v to be as high as 6.7. This will not be dangerous to a high-end piece of equipment that was made in anticipation of DC irregularity, but cheaper devices without better overvolt circuitry can get damaged. The only way to test it is with a reliable volt or multi-meter.

  39. Tina Sieber
    June 20, 2013 at 11:02 am

    For once, the European Commission used its power to the advantage of EU citizens.

    The European Commission has persuaded mobile-phone manufacturers to abandon the wasteful and inefficient production of different chargers for different phones. Fourteen of the leading phone-makers agreed on a harmonised system for data-enabled phones sold in the EU. The result on paper is new technical standards. The result in the shops - and in the pockets and handbags of EU citizens - is that all these phones can be charged with a simple micro-USB plug.

    Source: [Broken Link Removed]

    The agreement has been in effect since 2011.

    • Lisa Santika Onggrid
      June 20, 2013 at 6:46 pm

      If only governmetn could just stay with making 'good' rules like that instead of stupid rules no one would care for...

      • dragonmouth
        June 20, 2013 at 8:39 pm

        Not be pedantic but "good" for whom? The customer? The Manufacturer? Everybody has a different definition of what is "good" for them. There is a very good chance that what is "good" for the customer is not "good" for the manufacturer. Governments tend to follow the Golden Rule "He who has the gold, makes the rules."

        • Lisa Santika Onggrid
          June 22, 2013 at 1:04 pm

          I was clearly referring to customers, but you're right. You're not being pedantic. It's simply the truth. That rule is older than dirt.

    • Charlie O.
      June 20, 2013 at 9:11 pm

      Hello again, Tina. Excellent addition.

      Here's hoping that Corps will grow up a little and see the long term consequences of their actions - self steer - and avoid forcing us, in our respective representative forms of government, to force them to do what's right.

      I know most of the people here may not think like this, but I bet you're imagining a Fermi-like estimation of just how many discarded charger plugs are in landfills across the globe. I know I am.

  40. Sidharth Verma
    June 20, 2013 at 10:56 am

    “The world of electric power can be a little complicated. ”
    It is complicated on purpose by the manufacturers because different cables, different amp/volt ratings provides them with another way to lock in the suck.., I mean customers.
    This is nothing new. I run into this problem with printers all the time. I buy my printers (mostly HPs) at garage and tag sales. Each series of printers has a different shaped plug and a different power brick. Even when the plug is shaped the same, the power numbers of the printer could be different. Considering that over the years HP has made probably close to a hundred, if not more, different series of printers, it is very hard to re-use power bricks.
    I wonder how the auto industry would do if every model, or even only every manufacturer used a battery with different specs and/or cables.

    • dragonmouth
      June 20, 2013 at 12:21 pm

      Please try to think for yourself instead of blindly re-posting the comments of others.

  41. Chiranthaka Jayakody
    June 20, 2013 at 7:47 am

    A useful article !

  42. Min Xuan X
    June 20, 2013 at 5:10 am

    I have a question. Does higher amperage mean faster charging, or is it still the same for all chargers; the phone decides how much to draw from the charger?

    I have 3 different Nokia chargers, with 0.35 Amps, 0.45 Amps and 0.8 Amps. Does switching from the 0.35 Amp charger to the 0.8 Amp charger halves the charging time?

    • 3616833
      June 20, 2013 at 9:20 am

      It depends on the phone, if it can use 0.8 amps then yes it will charge faster with the 0.8 amp charger. If it can only use 0.35 then it will only pull 0.35 from the charger no matter how high the value is.

    • Ryan Dube
      June 20, 2013 at 7:39 pm

      As the other commenter just said - it does depend on the phone. The phone's current rating is a max - so the phone won't draw more than that rated current at any given time. So yes, the phone decides how much to draw - it uses what it needs. If it needs more than the charger is capable of, then it won't work.

      • Min Xuan X
        June 21, 2013 at 1:30 am

        Then does switching off the phone help? Since the phone uses less energy that way.

        • naresh
          June 21, 2013 at 5:50 am

          Yes, it might help. But though the phone is switched off, and it still needs more current than the charger can supply, it may not charge.

        • naresh
          June 21, 2013 at 6:03 am

          I have a question. Say charger 1 outputs 5.2V, 500mA and charger 2 outputs 4.9V, 500mA. Though the charging current depends on the smart phone's battery, can it also depend on the charger? I mean, the voltage level at which the charger outputs. Generally when batteries are charged at higher voltage, they tend to charge fast taking higher currents.

          My observation was the output of USB 2.0 port was around 4.9-5.0V and that of a smart phone charger (HTC) was 5.2V approx. So when I charge my phone via USB, it takes more time (charging at less current) and when the same is charged via charger, it takes less time (charging at higher current). The only difference in these cases is the current source with different voltages.

        • Doc
          June 21, 2013 at 6:13 pm

          USB's standard voltage is 5.0v; if the voltage is out of spec, whatever device is attached *could* be damaged, but probably won't with the examples you gave.
          Watts = volts * amps, so a higher voltage provides more current to charge the battery, so yes, it should charge faster unless the device lowers the amperage to provide a stable wattage, or uses a voltage regulator to protect itself. I'd still recommend using the manufacturer's charger or as close to "standard" 5.0v to protect the equipment.

  43. SH
    June 20, 2013 at 1:16 am

    Great post. There's another oddity with respect to Android phone chargers. Apparently Android phones are smart enough to throttle back the charging rate when plugged into the USB port on a laptop to prevent draining or damaging the laptop battery Some aftermarket AC chargers are designed in such a way that Android phones cannot tell that they are on AC and not on a USB port. This has the unfortunate consequence of substantially reducing the charging rate when using the AC charger. According to Amazon reviews, some enterprising folks have managed to fix the problem by opening the charger and soldering a connection between two specific pins.

    • Ryan Dube
      June 20, 2013 at 7:37 pm

      Crazy - I never heard of that. Will have to research and potentially do an article about it. Thanks for the tip!

      • White Wolf
        June 21, 2013 at 4:32 pm

        This is actually a usb specification. When data transfer is allowed, usb limits the charging current. This is done because of the possibility of the current passing through for charging interfering with the data signals. This is the reason a lot of android phones now have a "charging" option when you plug them into a computer which disables the data connection so the charging current is uncapped.

        The soldering he's talking about deals with soldering the two data pins on the usb cord, which makes the charging device a dedicated charging port.

  44. dragonmouth
    June 19, 2013 at 11:31 pm

    "The world of electric power can be a little complicated. "
    It is complicated on purpose by the manufacturers because different cables, different amp/volt ratings provides them with another way to lock in the suck.., I mean customers.

    This is nothing new. I run into this problem with printers all the time. I buy my printers (mostly HPs) at garage and tag sales. Each series of printers has a different shaped plug and a different power brick. Even when the plug is shaped the same, the power numbers of the printer could be different. Considering that over the years HP has made probably close to a hundred, if not more, different series of printers, it is very hard to re-use power bricks.

    I wonder how the auto industry would do if every model, or even only every manufacturer used a battery with different specs and/or cables.

    • SH
      June 20, 2013 at 1:20 am

      Not only printers. In the past half dozen years, I've had three IBM / Lenovo laptops, each with a different shape and size charger connection.

      Your auto analogy may actually come to pass - apparently electric cars (Tesla, Nissan Leaf) and plug in hybrids (Volt, Prius) all use different, proprietary charging protocols and systems.

      • dragonmouth
        June 20, 2013 at 12:18 pm

        Printers is the first thing that came to mind. I too have a couple of IBM laptops.

        If I am not mistaken, back in the dark ages when cars were just started being made, each maker had their own specs. Somehow I don't think we will see different charging protocols and systems for electric/hybrid cars. Strike that last. It would be a great way to eliminate competition, force them to build their own network of charging stations.

    • Ryan Dube
      June 20, 2013 at 7:36 pm

      I agree - there are so many other products like this. Not just power cords for printers and laptops, but what about ink cartridges? You would think the printer industry would have decided on a standard and gone with that - but these days the printer manufacturers make far more money on selling ink than they do on the printers themselves. Making a standard would put all that money at risk I suppose.

      • Donny
        June 21, 2013 at 5:55 am

        When the other company make a series of non-compatible charger and accessories for their products, Apple make it the other way. One of advantage of using Apple products is that you could borrow your friend's adapter and it will just works. I wonder what will happened to all other printers manufacturer when Apple produce their own printer, where the ink cartridges will work across different printer series.

        • Doc
          June 21, 2013 at 6:08 pm

          Not true. iPads require more amperage to charge than, say, iPhones and iPods, and any non-iOS devices (iPod nanos, for example) use different chargers. The latest iPads and iPod Touches also have moved to the Lightning connector, rendering all older "dock-connector" addons obsolete.

    • Charlie O.
      June 20, 2013 at 9:04 pm

      Again, Drag, you get right to the sweet spot. My prediction on cars is that Auto Mfgs will stick with the known money makers of repair/maintenance and "newer-shiny-er". Convenience of use = more repairs & maint = increased spending to keep it going as it gets older = easier to sell more shiny, new stuff.