How do you force something to take current?

Discussion in 'General Electronics Chat' started by Guest3123, Jun 16, 2016.

  1. Guest3123

    Thread Starter Member

    Oct 28, 2014
    312
    18
    So I charged my cellphone with 4x AA Eneloop Batteries in series last night. The current was 424mA, and was charging 1% at roughly 6+ minutes.

    The charger made by Anker, can charge the cellphone at roughly the same voltage, but at 1A.

    How do create or force current (Amps)?

    So a Benchtop power supply can force current threw things.

    How can I force current?

    I = E/R, I = P/E, I = the square root of P/R

    Great. So how is it done?

    So obviously, if I had a coil with a resistance of 2.1Ω, and put 4.2vdc threw it, it would glow red, and dissipate 8.4 Watts, allowing 2 Amps or 1.6x10^19 x 2 electrons to pass a given point, per second. That's really great.

    So basically, anything after the coil, or resistor in series receives the 2 Amps?

    No it doesn't because the device also has a resistance. So whatever the device resistance is, it shares or divides the resistance with the other resistor.

    How do you force current onto something?
     
  2. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
    4,771
    971
    The reason your batteries only supplied a certain amount of current is due to their own internal resistance.. They only allow a certain amount of current to be drawn from them..
    Same reason that one can get buy not having a resistor in a childs toy that is just a simple coin cell battery + LED circuit.. Normally a resistor is needed to "limit" the amount of current through the LED or the LED would blow up.. But as the batteries have their own internal resistance they can only supply so much at one time..
     
  3. joeyd999

    AAC Fanatic!

    Jun 6, 2011
    2,691
    2,756
    USB chargers are not "dumb" like batteries. They actually communicate, digitally, to negotiate the charge rate.

    IIRC, USB will nominally charge at 500mA passively. Communication and negotiation is required for higher rates.
     
    MrSoftware likes this.
  4. bertus

    Administrator

    Apr 5, 2008
    15,648
    2,348
  5. Guest3123

    Thread Starter Member

    Oct 28, 2014
    312
    18
    So if I used a 40C, 1S (4.2vdc), 3600mAh LiPo Battery, then it would work better? If I were to do that. LiPo batteries are known to supply constant voltages with far less voltage drops than a low end AA Battery..
     
  6. Guest3123

    Thread Starter Member

    Oct 28, 2014
    312
    18
    I don't see how asking what voltage my charger supplies has anything to do with the question I asked. But here's the information.

    The Anker 5 Port Charger supplies 5vdc @ 1A Constant.

    Again, I honestly don't know what that has to do with my question.

    The 4x Eneloop Batteries in series were supplying 5.3vdc @ 424A Constant.

    A USB 2.0 Port on my laptop supplies 5vdc @ roughly 500mA Constant.
     
  7. joeyd999

    AAC Fanatic!

    Jun 6, 2011
    2,691
    2,756
    Like I said, the charge rate is negotiated between the USB charger (or hub in the PC) and the device. This is a fact of life. Changing batteries will affect *nothing*.
     
  8. Guest3123

    Thread Starter Member

    Oct 28, 2014
    312
    18
    How do I get something to supply 1A @ 5Vdc.

    Even using the new 430 Watt Evga ATX Power supply today, that can give 5vdc @ 3A Constant, will more than likley NOT give me the full 3A.

    So how do I force batteries or a power source capable of supplying greater than or equal to 1A?

    Its circuitry, obviously.. So how is it done?

    Even if I had and used a 40C, 1S (4.2Vdc), 3600 mAh Nano-Tech LiPo Battery.. Which is capable of supplying 40 x 3.6 = 144 Amps (Minimum).
     
  9. joeyd999

    AAC Fanatic!

    Jun 6, 2011
    2,691
    2,756
  10. Guest3123

    Thread Starter Member

    Oct 28, 2014
    312
    18

    What kind of circuit will supply or force 1A @ 5vdc?
     
  11. joeyd999

    AAC Fanatic!

    Jun 6, 2011
    2,691
    2,756
    A USB charger that supports 1A charge rate and is compatible with your device.
     
  12. Guest3123

    Thread Starter Member

    Oct 28, 2014
    312
    18
    wow...

    So basically all I have to do is plug in my Anker USB Charger into the wall, and then plug my device in it, and charge at 1A.

    Which is does.

    Thanks so much for your help Joeyd999. That's exactly what I wanted to hear.
     
  13. bertus

    Administrator

    Apr 5, 2008
    15,648
    2,348
  14. joeyd999

    AAC Fanatic!

    Jun 6, 2011
    2,691
    2,756
    You are welcome. Unless you are being sarcastic. I cannot tell.
     
  15. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
    4,771
    971
    Seemed like sarcasm to me..
     
    GopherT likes this.
  16. wayneh

    Expert

    Sep 9, 2010
    12,151
    3,058
    If your phone was a dumb device like a lightbulb, you would increase the current to any level you like by increasing the voltage. There is no other way to make it take more. At some point you exceed what the device can tolerate, and it blows like a fuse.

    You phone is not a dumb device. There's no way to know how it would react to excess voltage. It might protect itself (up to some limit), or it might not, and turn itself into a fuse. Poof. No way I would experiment with mine.

    What Joey is trying to tell you is that your phone may be limiting itself, even if you are connecting an adequate supply. It tries to communicate with the supply, gets no reply from it, and limits itself to what you observed. People have had success placing certain voltages onto the data pins of the USB connector to initiate charging. You need to know which voltages your device needs to see, or spend some time experimenting.

    Your problem could be as simple as your batteries unable to supply 1A at 5V, or the phone doesn't call for 1A throughout the charging cycle, which I'm sure is true. Have you tried making a current measurement with your genuine charger?
     
  17. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
    4,771
    971
    As stated there is a "negotiation" that occurs..
    Seems some phones either look for shorted data lines or specific voltages on those 2 data pins.. (via voltage dividers)
    From that they go into fast or slow charging mode..
     
  18. joeyd999

    AAC Fanatic!

    Jun 6, 2011
    2,691
    2,756
    wayneh likes this.
  19. Guest3123

    Thread Starter Member

    Oct 28, 2014
    312
    18
    I'll just try a slightly higher voltage.

    Ok, so if the phone is getting 5vdc of voltage, and is only accepting 0.424A of current, than that means it has a resistance as a whole of 11.7924528301887Ω resistance.

    If that's true, which it is.. Then passing 6vdc, threw 11.7924528301887Ω of reistance (Note 4), then the current should increase to 0.508A

    and if I try to pass 10vdc, to the phone, with the phones internal ressistance of 11.7924528301887Ω, then my DMM should read something like 0.847A..

    That's too much voltage.. But I think I might be onto something.

    Current (The Ampere), doesn't come from thin air, it's generated. It's defined as an X amount of electrons passing a given point, per second.

    Voltage, on the other hand, is NOT an Ampere. But they co exist together, and are determined by Ohm's law.

    I = E/R, I = P/E, and last.. I = the sqr. rt. of P/R.

    Current (The Ampere) is equal to Voltage divided by resistance.
    Current (The Ampere) is equal to Power divided by voltage.
    and Current (The Ampere) is equal to the square root of Power divided by Resistance.

    One does not exist without the other. Ohm's Law 101.

    So..

    How the hell can I make more current.

    The Phone isn't alive. If I went out and bought something that someone else made (ANKER CHARGER) I could force the phone to take whatever the hell I wanted to give it, and the phone couldn't do jack about it, because it's stupid. It's an inanimate object. It's not living. And even a person is stupid, and if I wanted to put you in the electric chair, and pass 1000 Amperes of current threw your body, I could do so, because people are stupid.

    So.. Let's see here.. You saying that putting more voltage on it is a really good answer, but I could damage the phone, because I need far too much voltage to get 1A of current. Ohm's Law proves that giving more voltage, when the phone indeed has a resistance as a whole, would allow me to pass more current to the phone, by simply increasing the voltage. That's easy, and it's too easy, and in turn, would "YES" damage the phone if I took the voltage too high, because after all, the phone is stupid and is just a punch of plastic, metal, and chemicals.

    So I honestly need to sit and think a little bit, because I think just with the answer of the higher voltage, I could figure out the missing piece to the puzzle, just by using Ohm's Law.

    Ohm's law is smarter than the phone, it governs the whole idea how the phone is made. Without Ohm's Law, the phone doesn't work.

    So.. I need to sit and think for a while, until I can think of what the missing piece is.

    Thanks for the help so far, some really good answers from helpful people.
     
  20. joeyd999

    AAC Fanatic!

    Jun 6, 2011
    2,691
    2,756
    You phone may not be animate, but it is also not a resistor. It does not obey ohms law.
     
Loading...