All you ever wanted to know about battery chargersTips


  1. Idunno

    Idunno Well-Known Member

    I know a few people (including myself) have been wondering what is the best charger I can use for my phone... so essentially whats going to charge my phone the fastest. We have a few options, and it really comes down to how much power the charger puts out, for all intensive purposes all you need to know is Volts and Amps. USB connections all operate right around the 5.0 volt range (4.75v-5.25v depending on device/manufacturer), and anywhere between .5 amps (500mA) - 2.1 amp (2100mA). Just think of it like water, if volts are how much water is there, amps is the amounts of pressure pushing it through the pipe (wire). We are offered various voltage/amp combinations depending on what type of charger you use.

    So now that you have a little background lets look at specifics:

    Standard USB - Any USB port, any computer, anywhere will supply you with 5 volts and .5 amp (500mA) of output for charging power. That 1/2 amp used to be all you needed to charge mp3 players, phones, cameras etc... but with all these high end - high power devices .5 amps is getting to be not enough.

    A/C Chargers - This is where the most variation is as far as power output, they will all put out an acceptable voltage (4.75-5.25 volts), but anywhere from .5 - 2.1+ amps, and just about every value in between, .7, .8, 1.0 etc... so in theory the higher the amps the faster your battery will charge (more pressure in the pipes means the water is going to go in faster), kind of like if you trickle charge or quick charge your car battery.

    Car chargers - 12v (cigarette lighter) automobile chargers, i've seen .5 amp and 1.0 amp car chargers, all were 5 volt.

    For this test I used the stock Samsung 1.0 amp A/C charger that was supplied with the phone and a 2.1 amp Duracell A/C charger, charged for a while, noted the differences in time and charge, took a screen shot and ran the numbers so here they are. (note: USB charging was not taken into account because we all know it was going to be the slowest one anyway, the real comparison here is between wall chargers)
    [​IMG]

    The first big charging bump is the 2.1 amp Duracell charger. It charged for 1.33 hours (1 hour, 20 mins) which yielded a 36% increase in battery charge. Take note of the relatively shallow angle of the incline as it charges compared to the Samsung charger. This works out to 23.25% charge per hour, or 3.75 hours to go from 0-100%.

    The second big charging bump is the 1.0 amp stock Samsung charger. It was charging for the same 1.33 hours (1 hour, 20 mins) which yielded a 65% increase in battery charge. Notice how steep the incline angle is compared to the Duracell charger. This works out to 50% charge per hour, or 2 hours to go from 0-100%. When calculated it was actually 2 hrs 3 mins... but we aren't that picky right?

    So the results are rather interesting... the stock samsung charger outperformed the quick charger, you may be asking why? Well, its not defective because I originally thought that and got a replacement to run the test again... same result. So either duracell is crap brand of charger or there is a charge limiting mechanism in the phone (which I highly doubt, because then they both would have charged at the same speed, not different). This is good for me because I like to charge quickly, I don't like standing around waiting for things to juice up so I would always buy the highest amp charger I could find, I never actually tested to see if it was charging faster.

    Now its nice to know that the bone stock little charger they gave us not only beats other brands of chargers, but now we know that even with just 1.0 amp a full charge is only going to take 2 hours which in the long run is not bad at all. So in conclusion my friends... don't waste money on a fancy charger in IMO, the stock charger and one for the car to top up is all you need.

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  2. HarvesterX™

    HarvesterX™ Member

    Edit: Deleted huge post as it ended up straying way off topic by the end. Short story, my OEM Samsung wall charger was only picking up as charging in USB mode. Was going to short out the pins and just bypass usb altogether to see if it was the cable or something else... Instead figured I'd just try Force Fast Charge first before pulling out the equipment. Got it working perfectly, and according to Battery Monitor Widget it's drawing what it should be now, and I can ditch the old short og droid cable I had plugged into the wall port. Crisis averted. :)
  3. Idunno

    Idunno Well-Known Member

    what is this force fast charge you speak of?
  4. degg

    degg Member

    It is an option in some custom kernels, like Franco's. Normally the phone will only draw 500 mA if it is connected to a real USB port, but if it is a wall charger it will pull as much as it can take, or as much as the charger will deliver. The wall charger shows that it is a wall charger by shorting the two USB data lines. The Galaxy Nexus shows "Charging (USB)" or "Charging (AC)" depending on what it thinks it is connected to. The fast charge option makes it ignore the difference.

    Some wall chargers don't short the data lines, maybe that is the problem with the Duracell charger in the OP. Some USB devices don't check for shorted lines, but pull as much power as they can. This will not harm the USB port, unless it is badly designed.
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  5. Idunno

    Idunno Well-Known Member

    So how would I go about shorting the terminals/which ones do I short? I'm pretty sure this is exactly what's happening, because I didn't get 2 bad chargers in a row, and the "2.1A" is really only drawing .5A... it takes pretty much twice as long as the 1A. Now I'm interested, it's 5:00 am and I feel like going to walmart and buying some wire and pliers and having a go at this. This will be good for my study on chargers. Thank you.
  6. dhworph

    dhworph Well-Known Member

    this matches my experience of roughly 2 hrs for a full charge from empty on the OEM charger... good work! I love seeing the posts where people experiment like this and post data...
  7. Idunno

    Idunno Well-Known Member

    I'm going to update this as soon as I experiment with the shorting out the data pins trick mentioned above. This way I can compare USB, 1A a/c and 2.1A a/c, more thorough.
    jbdan likes this.
  8. jbdan

    jbdan Well-Known Member

    +1 thanks for this data!
  9. colchiro

    colchiro Well-Known Member

    FWIW, usb3.0 ports on newer computers should be able to output .9 amps.

    My Gigabyte computer at work also has an app that can be installed to enable more. See this: GIGABYTE 3x-usb-power

    My work computer has all 3.0 ports, but my laptop only has one.
  10. Tim K

    Tim K Well-Known Member

    If I am not mistaken, isn't it the phone that determines the amperage that it "accepts"? I was under the impression that if you put 1, 1.5, 2.0 amps to the phone, it will only accept a max of 1.0 amps. That prevents it from ever being fried by a charger putting out too much amperage.

    I'm not surprised the 2.1amp charger wasn't faster.... I would have expected it to perform identically to the 1.0 amp charger.... I am a little surprised it is that much slower. I wonder how the phone is wired to only take 1.0 amps. I guess there's an internal resistor...and it must be less than 1.0 amps.
  11. stoli40

    stoli40 Member

    Hi all, I don't post much hence the new user status, but I read forums a lot.
    My next couple of posts are just to correct some mis info. Sorry if they come across as trolling.
  12. stoli40

    stoli40 Member

    Tim K is right. The phone/battery has a regulator which controls the current draw from the charger. The phone only takes what it needs based on it's max current draw.
    It's hard to find the specs sometimes, but most phones top out at 1A of draw. So plugging a 2.1A source isn't going to charge your phone any differently if all it will draw is 1A.
    As Tim mentioned, this stops someone connecting their phone to a 5v 20amp source and turning it into a bomb.

    There's a good discussion about it here:
    Max safe amps for car charger in us?

    So why were your results different for each charger?

    Sorry to say but your experimental method is flawed.

    Firstly have a look at the 'screen on' bar in your picture. You can see that the screen was on more in the Duracell test than in the OEM.
    This has a huge impact on charging rates as the screen is generally the biggest consumer of power.
    Also, your phone consumes power at different rates at different times depending on what apps are running (CPU usage) and whether they download data (WiFi usage even if it's 'on' for both tests).
    This is also true for the charging cycle. Even though the max draw might be 1A, the phone might not be drawing it all the time. This is largely dependent on the controller and the OS.
    I mention this because you performed each test sequentially and the drain/charge variables were probably different for each test. You can't tell from your graph and in fact, to know the exact draw (charge)/drain (usage) at any one time would require a graphing multi-meter for both current and voltage. If you don't have a Motorola or Samsung, try 'current widget' on the apps market to do this.

    Secondly, Li-Ion batteries and their controlling circuits are complex bits of kit and they don't charge at a linear rate throughout the battery cycle regardless of what the phone is doing. The rate from 0-50% or 25-75% or 50-100% is different even without the phone being turned on.
    Again, I mention this because you started each test sequentially at a different level of charge.
    Also, temperature greatly affects Li-Ion batteries and their charge/discharge rate. Unless the temp was maintained constantly throughout, it would affect the charge rate.
    Ask any tradie using Li-ion power tools about the difference between a hot and cold day and they'll tell you the difference in battery performance.
    Also, have you ever run out of power using a digital camera on Li-Ion batteries? Try warming them up with your hands or body heat to squeeze out a few last shots. Same temp principle here.

    Lastly, your final results of time were based on linear extrapolation in a non-linear environment. You applied the same formula to both, which is fine if you're just comparing two things, but the final 0-100% time doesn't stack up. Particularly as Li-ion trickle charge towards the end.

    Add all this up, and it's not surprising the charging results were different. Too many variables.

    If you want to have another go, try this:

    Run your battery down until the phone shuts down.
    Let it sit for 15mins to let the battery get to room temp.
    With the phone off, start charging.
    Check the indicator at 30mins, 1 hr, 1.5hrs, 2hrs then every 15mins from there until the phone indicates the battery is full. Some phones might play a tune when this happens.
    Record the time within a 15min bracket.

    Repeat with the other charger EXACTLY as before, including frequency of the check intervals. (checking more will run the screen more)

    If you really want a semi-valid result. Repeat two more times.

    My guess is that the results should be similar. Within 15mins I'd say given other uncontrollable variables.

    Again, I'm not here to poke holes, but when you title the thread
    "All you ever wanted to know about battery chargers" , publish results so emphatically and others think it's right, someone needs to say something.
    There's a reason why the term "controlled experiment" exists.
    But good effort for trying. :)
  13. stoli40

    stoli40 Member

  14. tmach

    tmach New Member


    Not trying to troll, but this may only be partially correct. It really could be an issue with the charger since car chargers suffer from this same problem. Here's why:

    It's true that many phones will only accept a max of 1A no matter what, but it doesn't explain why a 2.1A universal charger was only delivering .5A. The phone should still draw 1A, just like its standard wall charger, so why doesn't it? The answer to that lies in the charger, the phone, and/or the cable used to connect them.

    Most smartphones will assume, once they're connected to a standard USB port with a standard USB cable that they are connected to a computer. At that point, they will only accept .5A. This is a big problem with car chargers, since it means the phone won't draw enough power to be able to charge and use things like bluetooth and GPS at the same time. The battery will still drain, because it isn't getting enough juice.

    So why does the phone assume it's connected to a computer when connected to a car charger or some universal chargers? It's because of the data pins, which are 2 & 3 on standard USB. These pins are bridged in wall chargers (or may not even be there at all) so the computer sees it as a power-only connection and draws what it can. In some universal (and just about every car) charger, the pins are left alone and the computer sees it as a data/power connection and reduces its draw. Why they leave the pins like that, I don't know. Maybe some phones need it for something, but no Android phone I've used needs data pins just to charge the phone.

    There are two things you can do to fix this: Use a charge-only USB cable or, if you don't want to buy another cable that's useful only for charging, you can open up the charger and bridge pins 2 & 3 with a bit of solder. That should make the phone see your charger as a regular wall charger and draw the max power it can.

    I've only ever needed this for the car so I use a charge-only cable, but there are a few guides out there for bridging the pins to modify chargers if you need them.
    mllyou likes this.
  15. stoli40

    stoli40 Member

    Thanks for that but as far as I know any decent brand of AC charger will ship with a decent cable, Duracell included. I can't say whether the original poster swapped out the cables, but he'd have to be REALLY daft to try compare 1A vs 500mA charging rates then publish them.
    Also, there's not enough of a difference in results to indicate the cable issues you mentioned. If the Duracell charger was only delivering 500mA, the difference would have been MUCH bigger, especially considering the other factors.

    The things I've said are either true or not. They can't be 'partially true'.
    If the charging ability of the cable was the same (which I believe it was) then the comments stand.
    If the charging ability of the cable was different (ie 1A vs 500mA) then the difference in results would have been much greater.
    You can work the rest out from there.

    The problems you describe tend to occur in car chargers (as you mentioned) and people using cheap USB cables to plug into AC chargers. Stick to a decent USB cable, not a 2c string off eBay and they should be fine. You can check in 'settings' to see whether the phone thinks it's plugged into AC (1A) or computer USB (500mA) when charging. Or download current widget and see the actual charging current.
  16. frankws

    frankws New Member

    I wish someone with a degree in this would state their qualifications and give us true facts. There are too many opinions here to really know what is safe to use and what isn't.
    IDUNNO says, A/C Chargers - This is where the most variation is as far as power output, they will all put out an acceptable voltage (4.75-5.25 volts)
    Then why does the one I purchased say, Output 7.6 volts-1000mA?
    Someone says 2 amps turns the phone into a bomb but others say it's the volts or amps that affect it and damage it.
  17. colchiro

    colchiro Well-Known Member

    I use my HP Touchpad 2 amp charger to charge everything:

    Hp Touchpad
    Google Nexus 7 tablet
    Samsung Google Nexus phone
    Motorola DroidX phone
    Harmony One remote.

    Only the first two devices require 2 amps. The rest are between .75 and 1.5 amps. No explosion, no smoke, no flame. :D

    If the output is 5 volts, it shouldn't matter what charger you use as long as you use a compatible cable.

    I have a Nook Color tablet that has a proprietary cable that shows orange when charging and green when fully charged. I can use the HP Touchpad charger for this but need to use the NC cable.
  18. Lautermilch

    Lautermilch Member

    I was searching for this thread after noticing how fast my Samsung charger that I got with my Nexus a few weeks ago charges. The other charges I use at work and my car charger are so sloooooow to charge.
  19. colchiro

    colchiro Well-Known Member

    There's a reason they made the micro-usb plug standard for phones and tablets... they're designed to be interchangeable.

    Obviously it's best to use the higher output ones tho. :D
  20. peterhoth

    peterhoth New Member

    Hi,

    I need advise for the following:

    Charger A (Li-polymer battery) output : 5V, 1A
    Charger B (Li-polymer battery) output : 5V, 500mA
    Device input: 5V, 750mAH (Li-ion / Li-polymer)

    When using Charger A, some people comment that it will limit the current of 750mAH for the device and the device's battery should be fine since both the charger and device are at 5V. However, some people comment that this will shorten the battery life of the device since it will perform a 'quick charge' using 1A.

    When using Charger B, some people comment that the device will draw more current than it can deliver and causes it to heat up and reduces the charger's life. However, some people comment that Charger B will extend the battery life of the device since it performs a 'slow charge'.

    I also read that USB pins on the charger denotes if the charger is a PC or a dedicated charger. If it is a PC, the device will limit the drawing current. If it is a dedicated charger, the device will draw more current to charge itself.

    I am confused as to who is right and which charger should i be using.

    Can someone enlighten me ?

    Thank you very much.
  21. colchiro

    colchiro Well-Known Member

    Where's the stock charger for your 750 mAH device? It's always best to use the stock charger and stock cable, when you have a choice.

    Your device determines how fast it will charge. Using a charger that has more current capacity will not ruin it if the voltage is the same. (All usb chargers should be 5 volts.) if it gets hot or acts goofy while charging or complains (incompatible charger), then don't use it.

    The cable you use often makes a difference too. When possible, try to use the original cable. My wife has a Nook Color with a special cable with an LED that shows orange when charging and green when fully charged. Although I can use other chargers with it, I have to use the stock cable, which must have extra pins. I also cannot use that cable with other devices.

    Regarding your question, you can use either charger, but the smaller one will charge slower. Slower charging and not charging to 100% will make your battery last longer in theory, but batteries are cheap. Fully discharging your battery on a regular basis will greatly decrease it's life a lot more than which charger you use.
  22. TheyCallMeBT

    TheyCallMeBT Well-Known Member

    So my 6 ft.+ Blackberry charger died (frayed). The one that came with the phone was fine for charging at my desk, but I need a 6 ft one or even a 7 ft to charge at night and be able to use the phone while plugged in. Anyone have any specific links to either chargers or cables (that can be used with a bare USB plug charger-- link for that, too) that charge full speed for the GNex?

    I know that Amazon started something new where you have to buy like $25 or around that when buying small cheap items like this. But I actually want to buy a few for stocking stuffers, so if that's all you have, that's fine. Thanks!!
  23. sperho

    sperho Well-Known Member

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  24. TheyCallMeBT

    TheyCallMeBT Well-Known Member

    Perfect! Thanks. The Amazon link in the article was good. Then I'm getting a couple of cables on Monoprice, along with a couple of USB extender cables. Good stocking stuffers for family members that are also tired of short phone chargers. Thanks!!
  25. colchiro

    colchiro Well-Known Member

    I use my HP Touchpad charger for everything. It charges my Nexus 7 better than the charger that came with it. :D

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