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  1. Thread Author  Thread Author    #1  

    Default Max safe amps for car charger in us?

    I don't want to fry my S3 or cause a car fire!

    Do they make ones with max amps that can charge two S3 phones at once? (max amps to both at same time?)

    Thanks!

    Sent from my SAMSUNG-SGH-I747 using Tapatalk 2
  2. #2  

    Default Re: Max safe amps for car charger in us?

    Do they even make a Y spliter for micro USB's?
  3. #3  
    sparksd's Avatar

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    Default Re: Max safe amps for car charger in us?

    Quote Originally Posted by jcp006 View Post
    Do they even make a Y spliter for micro USB's?
    There are car chargers with dual USB slots allowing the simultaneous connection of two charging cables.

    http://www.amazon.com/gp/product/B00...idcentral00-20

    Dave
  4. #4  

    Default Re: Max safe amps for car charger in us?

    At 2.1 amps, that's going to be a quick charge. Can the GS3 handle that much current as the OEM is, I believe, a 700 mAh.
  5. #5  
    sparksd's Avatar

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    Default Re: Max safe amps for car charger in us?

    Quote Originally Posted by jcp006 View Post
    At 2.1 amps, that's going to be a quick charge. Can the GS3 handle that much current as the OEM is, I believe, a 700 mAh.
    With a standard USB data cable the phone recognizes it as a USB charging source and only pulls 500 mA. You can get "charging only" cables allowing higher (still safe) amperage --

    Amazon.com: Naztech Micro USB Charging Cable - BlackBerry, Cal-Comp, HTC, LG, Samsung, Nokia, and Sony Ericsson: Cell Phones & Accessories

    Dave
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  6. #6  

    Default Re: Max safe amps for car charger in us?

    Quote Originally Posted by sparksd View Post
    With a standard USB data cable the phone recognizes it as a USB charging source and only pulls 500 mA. You can get "charging only" cables allowing higher (still safe) amperage --

    Amazon.com: Naztech Micro USB Charging Cable - BlackBerry, Cal-Comp, HTC, LG, Samsung, Nokia, and Sony Ericsson: Cell Phones & Accessories

    Dave
    In other words, in most cases, it would charge both phones or one phone at a slower rate then the OEM. Still probably worth it.
  7. #7  

    Default Re: Max safe amps for car charger in us?

    Amazon.com: Samsung OEM Galaxy S Micro-USB Dual Male Y Adapter: MP3 Players & Accessories

    This is a Samsung micro USB dual male y adaptor. It is compatible with the Note. I looked on Samsung's website and it does not list the GS3 as being compatible but that may be due to how new the GS3 is. Does anyone know if the Note pin configuration is the same as the GS3?
  8. Thread Author  Thread Author    #8  

    Default Re: Max safe amps for car charger in us?

    Quote Originally Posted by sparksd View Post
    With a standard USB data cable the phone recognizes it as a USB charging source and only pulls 500 mA. You can get "charging only" cables allowing higher (still safe) amperage --

    Amazon.com: Naztech Micro USB Charging Cable - BlackBerry, Cal-Comp, HTC, LG, Samsung, Nokia, and Sony Ericsson: Cell Phones & Accessories

    Dave
    OMG: Dave made a huge point here: I always bought usb sync/charge cables because I figured they were the same price, why not have the extra versatility of being able to sync too!

    OK. I'll definitely get the charging only cables so I'm able to get more than .5 amps.

    Now the only question remains is if it will fry my new S3 at 2.1 amps.

    If 2.1 amps is fine, why did Samsung only ship with .7 amps? (Wouldn't they want their devices to charge as quickly as possible if there were no downsides?

    Thanks again Dave!

    Mike
  9. Thread Author  Thread Author    #9  

    Default Re: Max safe amps for car charger in us?

    Is the answer that the phone only sucks .7 amps, so any more on the charger side would not be used?

    Is that why you can safely charge an iphone with an ipad charger? (the phone only sucks as much as it wants)?

    (I do recall that you may NOT plug an ipad into an iphone charger because the ipad will suck too much power and will overload the iphone charger.

    Mike
  10. Thread Author  Thread Author    #10  

    Default Re: Max safe amps for car charger in us?

    Wait a second: isn't the charger that came with the Galaxy S3 a charge & SYNC cable which plugs into the wall adapter? If all this is true, shouldn't the charging from the wall be a slow .5 amp (usb speed)? It seems MUCH faster than that.

    What am I missing?

    If it's the cord that determines the rate, how could I be getting fast charges from the provided cord plugged into the wall adapter?

    Mike
  11. #11  

    Default Re: Max safe amps for car charger in us?

    Quote Originally Posted by pcguys View Post
    Wait a second: isn't the charger that came with the Galaxy S3 a charge & SYNC cable which plugs into the wall adapter? If all this is true, shouldn't the charging from the wall be a slow .5 amp (usb speed)? It seems MUCH faster than that.

    What am I missing?

    If it's the cord that determines the rate, how could I be getting fast charges from the provided cord plugged into the wall adapter?

    Mike
    For a wall/car charger the data pins may be shorted together internally, so it doesn't matter what cable you use. If a generic wall/car charger is designed for the iPad, it uses Apples weird way of signalling to the device that it can draw full power. Instead of shorting the data lines Apple provide a specific voltage on the data lines (2.0 or 2.8 volts IIRC) to tell the device how much voltage it can pull. By using a charging only cable you are tricking the device into drawing maximum power.
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    Default Re: Max safe amps for car charger in us?

    Sorry for being slow on this, and ignoring the iphone/ipad issue for the moment:

    If a charging-only cable tricks the phone into drawing maximum power, then how does the stock charge + sync cable provided by samsung charge faster than USB (since their cable is a removable USB cord)??

    Mike
  13. #13  
    sparksd's Avatar

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    Default Re: Max safe amps for car charger in us?

    I took a look and using the Amazon dual-port 2.1A charger I referenced above, my S3 battery status says Charging (AC). Using the same cord but plugging into a laptop USB port, it says Charging (USB).

    Dave
  14. #14  
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    Default Re: Max safe amps for car charger in us?

    snip - accidental double post. Sorry

    Dave
  15. Thread Author  Thread Author    #15  

    Default Re: Max safe amps for car charger in us?

    Quote Originally Posted by camiller View Post
    For a wall/car charger the data pins may be shorted together internally, so it doesn't matter what cable you use..
    Having re-read this thread again, it sounds like CaMiller's point is important:

    A fancy wall or car charger can be designed in such a way that it doesn't matter if you use a sync cable vs. a charge-only cable).

    Mike
  16. #16  

    Default Re: Max safe amps for car charger in us?

    Quote Originally Posted by pcguys View Post
    Having re-read this thread again, it sounds like CaMiller's point is important:

    A fancy wall or car charger can be designed in such a way that it doesn't matter if you use a sync cable vs. a charge-only cable).

    Mike
    Right. But it is important to re-iterate that if the wall or car charger is made for/targeted at Apple devices (which for some unfathomable reason seem to be popular ) an Android device is likely to see it as USB instead of AC.

    So if the advertising copy says it charges your iPad and Android devices, it most likely will charge the Android device at the slower rate.
  17. Thread Author  Thread Author    #17  

    Default Re: Max safe amps for car charger in us?

    I think I'm going to stick to the suggested links for the charger & cables above.

    Thanks everyone!

    Mike
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    Default Re: Max safe amps for car charger in us?

    I use a 2.1 amp USB charger in my car and my s3 has been fine.

    All chargers these days (unless you buy some POS for 50 cents) trickle the last bit so you dont overcharge and thus ruin your phone.

    and FYI, the stock charger that came with the s3 (at least on Verizon) is a 1 amp charger.
  19. #19  
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    Default Re: Max safe amps for car charger in us?

    oops duplicate
    Last edited by snork; 07-30-2012 at 04:04 PM. Reason: duplicate
  20. Thread Author  Thread Author    #20  

    Default Re: Max safe amps for car charger in us?

    Quote Originally Posted by camiller View Post
    Right. But it is important to re-iterate that if the wall or car charger is made for/targeted at Apple devices (which for some unfathomable reason seem to be popular ) an Android device is likely to see it as USB instead of AC.
    .
    Now I'm feeling really dumb:

    Since I do have an iPad also, if I got one of the car chargers that mention iPad, but use a charge-only cable, will my android still charge slow?

    Mike
  21. #21  
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    Default Re: Max safe amps for car charger in us?

    I am surprised no one has piped up a little basic electricity here. A device draws the power its can use. The power is regulated to the battery to control the charge. The regulator is in the battery. But a laptop USB port with a power capacity of 2.5w can never provide more than what its capable of. 5 volts at .5 Amps = 2.5 watts. Your wall wart (car plug) is capable of more than that. I have wall warts rated from 10 watts (5V. x 2A) to 5 watts. (5V x 1A).

    There must be some sort of use of the data lines to signal to the phone the limits so it can indicate USB or AC. I guess the regulator could be smart enough to conclude which it is based on the initial charge rate which would be the time of highest draw.

    So, the maximum capacity of the power source will affect how fast a charge it is capable of, but the regulator of battery will control and limit the power consumed to what it decides is the right level. I have a 12v. 50A power supply to power my 100 watt radio transmitter. I could slap a big 5 volt regulator on it to control the voltage and use some car battery jumper cables to my phone (nice image, eh?) and the phone would be just fine.
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    Default

    I am also getting really dumb lol. Ever'm after all the explanations. Here is the question I want to know...

    Assuming this phone has a max of charging at 1 amps then if I bought a 1.8 amp charger it would only charge at 1 amps?
  23. #23  
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    The answer to your question is yes. If the maximum draw of your device is 1 Amp and you connect it to a 1.8 Amp charger it will draw 1 Amp.

    It will charge at the maximum safe rate determined by the regulator in the phone. The current is referred to as current DRAW. That is, the unit being powered will draw current from the charger at the rate it consumes it. Until you hit the max of the supply, when it will not go up any further.

    Think of this like a household light bulb. The voltage is 110v. Let me make the math easier to do and lets pretend its 100v. Your house has a master fuse of 100 Amps. The max power you can draw before the fuse blows is 100x100=10000 watts. Your 100 watt light bulb does not blow because 100 amps is available, it draws what it needs. 1 Amp. 100v x 1A = 100 watts. Remove the bulb and replace it with a 50 watt bulb. The current draw drops to .5 Amp because thats what it needs. 100v x .5 Amps = 50 watts. But if the electric company is having a bad day and only 45 watts is available to your house, the 50 watt bulb will dim because its draw exceeds the max available. Your light bulb is not harmed by the fact 100 Amps is available to it.

    The battery in your phone is not like a light bulb. Its a smart device. It is capable of controlling its rate of charge and, as the battery fills, it reduces the charge until it is full and stops charging altogether. An automobile battery charger does the same thing, hard charge at first, taper off as it fills, trickle when its full. So, if your charger is capable of 1.8, but your phone is limited to 1.0 there is excess capacity available at the charger. Get a Y connector and plug in another phone. If your charger is capable of 50 A. get 50 Y connectors and plug in 50 phones. There is no harm in having more capacity than any single device requires.

    Now all this applies to current capacity, but not voltage. Plug your phone directly into 100v and watch your teeny lil regulator cook itself to death in but a tiny little instant. All USB chargers are always 5 volts.

    A moment, if I may on the cables to connect to the charger. Every piece of wire has resistance. The resistance of the wire consumes power by turning it into heat. The resistance of a given piece of wire is a matter of its diameter and length. For our purposes the length is short enough that the amount of heat generated is negligible. What do you get in a "charging cable" ? Maybe a lil larger diameter wires on the charging lines. I bet not. I bet its a marketing scam. I have never felt a USB cable get warm while in use charging. I got one of these lil cables on a retractor that winds it up when not in use. The wire bundle is really thin. I have never felt it get warm even when used to charge my tablets. I have never noted a slower charge when using it over one of my larger cables.

    I do note that my little Sedio charging stand charges my phone slower that directly connecting the phone to the cable. Why? It has some electronics in it that deals with and lights some led's. That consumes power leaving less available for the phone. If I connect it to a 2A charger instead of the one that came with my phone I bet the charging rate goes back up to the full rate. Will I harm anything by doing so? Nope, not a chance.

    Sent from my cm_tenderloin using Android Central Forums
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  24. Thread Author  Thread Author    #24  

    Default Re: Max safe amps for car charger in us?

    Excellent explanation JaltMan, very informative!

    So, my only remaining question before I buy them is CaMiller's point about proprietary signaling for car chargers designated as ipad/iphone.

    Is there one that will charge an ipad AND an android at full speed using a charging cable?

    Thanks All,

    Mike
  25. #25  

    Default Re: Max safe amps for car charger in us?

    Quote Originally Posted by jaltman View Post
    The answer to your question is yes. If the maximum draw of your device is 1 Amp and you connect it to a 1.8 Amp charger it will draw 1 Amp.

    It will charge at the maximum safe rate determined by the regulator in the phone. The current is referred to as current DRAW. That is, the unit being powered will draw current from the charger at the rate it consumes it. Until you hit the max of the supply, when it will not go up any further.

    Think of this like a household light bulb. The voltage is 110v. Let me make the math easier to do and lets pretend its 100v. Your house has a master fuse of 100 Amps. The max power you can draw before the fuse blows is 100x100=10000 watts. Your 100 watt light bulb does not blow because 100 amps is available, it draws what it needs. 1 Amp. 100v x 1A = 100 watts. Remove the bulb and replace it with a 50 watt bulb. The current draw drops to .5 Amp because thats what it needs. 100v x .5 Amps = 50 watts. But if the electric company is having a bad day and only 45 watts is available to your house, the 50 watt bulb will dim because its draw exceeds the max available. Your light bulb is not harmed by the fact 100 Amps is available to it.

    The battery in your phone is not like a light bulb. Its a smart device. It is capable of controlling its rate of charge and, as the battery fills, it reduces the charge until it is full and stops charging altogether. An automobile battery charger does the same thing, hard charge at first, taper off as it fills, trickle when its full. So, if your charger is capable of 1.8, but your phone is limited to 1.0 there is excess capacity available at the charger. Get a Y connector and plug in another phone. If your charger is capable of 50 A. get 50 Y connectors and plug in 50 phones. There is no harm in having more capacity than any single device requires.

    Now all this applies to current capacity, but not voltage. Plug your phone directly into 100v and watch your teeny lil regulator cook itself to death in but a tiny little instant. All USB chargers are always 5 volts.

    A moment, if I may on the cables to connect to the charger. Every piece of wire has resistance. The resistance of the wire consumes power by turning it into heat. The resistance of a given piece of wire is a matter of its diameter and length. For our purposes the length is short enough that the amount of heat generated is negligible. What do you get in a "charging cable" ? Maybe a lil larger diameter wires on the charging lines. I bet not. I bet its a marketing scam. I have never felt a USB cable get warm while in use charging. I got one of these lil cables on a retractor that winds it up when not in use. The wire bundle is really thin. I have never felt it get warm even when used to charge my tablets. I have never noted a slower charge when using it over one of my larger cables.

    I do note that my little Sedio charging stand charges my phone slower that directly connecting the phone to the cable. Why? It has some electronics in it that deals with and lights some led's. That consumes power leaving less available for the phone. If I connect it to a 2A charger instead of the one that came with my phone I bet the charging rate goes back up to the full rate. Will I harm anything by doing so? Nope, not a chance.

    Sent from my cm_tenderloin using Android Central Forums
    The way the USB battery charging spec of 2007 is written ( sorry I don't have a link to the spec handy), the device knows it can draw up to 1.5A if the two data lines are shorted together. A "charging cable" does this internally, probably at one end or the other. A AC to USB adapter or car charger can do this internally as well by shorting the data pins together.

    Apples 10W/2A charger puts 2.8v on one of the data lines and 2v on the other (I forget which is which) to tell an iPad that it can pull up to 2A. Earlier iphone/ipod wall chargers put 2v on each data line which will limit the device draw to 500mA.

    This is why you need to use a "charging cable" with wall/car chargers made for apple products. The Apple oriented chargers do not internally short the data lines so most android phones will treat it like a 500mA source. The charger that ships with your android phone has the data lines shorted internally so it doesn't matter what cable you use.
    Last edited by camiller; 07-31-2012 at 08:27 AM.
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