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Need Help with Understanding And Changing a Circuit Diagram

  1. Aug 25, 2015 #1
    I am by NO means an electrical engineering student, so please explain it to me like I'm 5.
    My friend sent me a circuit diagram and I don't know how it works/what it means, but basically I want to know if it's possible to charge 2 batteries at once instead of 1, using the same mechanism. If so, how would I?
    Thanks!!
     

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  3. Aug 25, 2015 #2

    meBigGuy

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    It's not even a complete diagram for charging 1 battery, much less 2.

    What do you plan to connect as the "charging mechanism"?
    What kind of batteries?
    Is this a stand alone charger or do you have to charge while supplying power.

    Describe a bit more about what you are actually trying to accomplish.
     
  4. Aug 25, 2015 #3
    Well, I'm trying to learn some circuit 101 here that applies to my project.
    Basically, what type of voltage regulation and circuitry would I have to incorporate to charge not only 1 battery, but two. Both would be lithium ion but of different voltages.
     
  5. Aug 25, 2015 #4

    davenn

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  6. Aug 25, 2015 #5

    sophiecentaur

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    Charging batteries in parallel is not always a good idea and definitely not if they are different voltages. Lithium Ion are particularly fussy about the way they need to be charged. If you know as little as you claim then it could be dangerous for you to get involved. (That is not an overstatement.)
    Charge one at a time or, preferably, use two different chargers which are suitable for each battery.
     
  7. Aug 25, 2015 #6
    I see. Couldn't I just use two separate voltage regulators so that voltage isn't a problem?
     
  8. Aug 25, 2015 #7

    davenn

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    no,
    reread Sophiecentaur's second sentence ....
    which is why I posted the link to ideas, there were many other links on google
    for Li-ion, Li-PO batteries, the voltage, current and timing of the charge all need to be considered :smile:

    Dave
     
  9. Aug 25, 2015 #8

    meBigGuy

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  10. Aug 26, 2015 #9

    sophiecentaur

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    A "Voltage Regulator" is NOT what you need, for charging Li (or many other types of) batteries. You can easily EXPLODE an Li battery if you don't treat it nicely.
    What you are discussing, constitutes a dangerous practice. If you are not careful, the mods will close this thread. :))
     
  11. Aug 26, 2015 #10
    Understood.
     
  12. Aug 26, 2015 #11

    sophiecentaur

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    But don't be put off by that. There is loads to say about the different charging methods for the various battery technologies.
     
  13. Aug 26, 2015 #12
    I was also wondering how multiple things could charge one battery (safely of course). Could I get some circuitry information on that too?
     
  14. Aug 26, 2015 #13

    sophiecentaur

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    The way to approach this would be to use the different sources (wind, pedal, solar etc.) to combine in a single source - perhaps a large master-battery. That would buffer the variables in the source from the requirements of the battery to be charged. This is, of course, what the mains supply does all the time.
     
  15. Aug 26, 2015 #14
    What if I was using say, 3 solar panels and wanted to charge one large (lithium ion) battery? What circuitry would I need there? Each panel may gather different voltages, and I'm assuming as with before, Li-Ion are finicky so I'd need to do something different?
     
  16. Aug 26, 2015 #15

    sophiecentaur

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    Are you assuming the panels are nominally the same voltage and that one may begetting more sun than the others? The characteristics of solar panels are not as straightforward as you might be assuming. This link shows a typical V/I characteristic and you can see that there is a big range of voltages as the device starts to hit its current output limit. This, I think, would imply that you could connect more than one panel in parallel (with a reverse protection diode in series with each) and they would settle down into sharing the currents according to the illuminance. This would not be the most efficient solution though. If you wanted the most out of such a system, you would need a switch mode regulator in each circuit. Certainly not a beginner's project. If the panels were cheap enough, you could point each one around the ecliptic plane and get a high voltage out at all times of day. But I think that would be an expensive solution, even though panels are dropping in price.
     
  17. Aug 26, 2015 #16

    meBigGuy

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    Google "li-ion energy harvest"
    Contrary to what others say, there are lots of solutions to choose from
    IC's for energy harvest:
    http://www.linear.com/product/LTC4071

    This article explains the technology area you are in:
    http://www.eetimes.com/document.asp?doc_id=1273070

    This has pointers to reference documents:
    http://www.ti.com/paramsearch/docs/...og&familyId=3057&uiTemplateId=NODE_STRY_PGE_T

    Here are some more references:
    http://www.digikey.com/en/articles/...y-effectiveness-for-energy-harvesting-systems
    http://www.digikey.com/en/articles/...ify-backup-power-in-energy-harvesting-designs
    http://www.digikey.com/en/articles/...li-ion-battery-charging-for-energy-harvesting

    One solution is to simply buy a board that charges LI-ion batteries from solar panels.
    http://www.adafruit.com/products/390?gclid=CPL40bKiyMcCFYU5aQodb7wLGw (needs a 6V panel though)
     
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