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I can’t find out how amps are converted to volts

Shaye2 | Posted in General Questions on

As I said in an earlier thread I am making a solar powered usb charger. My solar panels have more than enough amps for the charge but the volts are behind at 7.71 and needs to be at 12. So my question is this: How are amps converted and how many amps WILL BE converted to supply the needed 4.3 volts more?
This is by far my favorite solar site.

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  1. GBA Editor
    Martin Holladay | | #1

    First of all, since you already started one thread on this Q&A forum, you should post all of your follow-up questions on the same page, instead of starting a new thread with your second question.

    I'll answer your question, however. The voltage of a PV module is determined by the number of solar cells in the module. This voltage is fixed. Each solar cell produces 0.5 volt. Two cells produce 1 volt; 6 cells produce 3 volts; 24 cells produce 12 volts.

    While it is possible to boost the voltage of this type of DC source with electronics, it's far simpler to just choose a PV module with the voltage that matches your needs. If you need 12 volts DC, purchase a PV module that produces 12 volts DC (or a little more) instead of a PV module that produces 7.7 volts.

    Another approach is to obtain two PV modules that produce 7.7 volts and wire them in series. (Connect the positive output of one module to the negative output of the other module, just like when you put two batteries in a flashlight.) Wired in this way, the two PV modules will produce 15.4 volts -- a good voltage for charging a 12-volt battery.

  2. Shaye2 | | #2

    Is there a way that i can combine this one to the other one? And thank you for the response.

  3. GBA Editor
    Martin Holladay | | #3

    Once you have created two threads on this site, there is no way to combine them.

    Q. "I can't find out how amps are converted to volts."

    A. The reason is simple; amps can't be converted to volts. Amperage and voltage are two different qualities of electricity. To make an analogy: you can convert inches to centimeters, but you can't convert height into weight.

  4. wjrobinson | | #4

    P=VxI so with a transformer voltage can be increased and the amps will decrease proportionately with some loss due to efficiancy which shows up as heat.

    Like Martin said much easier to buy what you need though there are sites on the net where folks tinker and create all kinds of home made stuff. Pop Sci is one along with check Pop Mech and others.

    Here's a site with basic formulas for electricity.

  5. Expert Member
    Dana Dorsett | | #6

    What exactly are you trying to charge with the PV? How many amps of +12V do you THINK you need? How many amps of 7.7V can/does your panel deliver.

    Most USB as in "Universal Serial Bus" devices operate at a nominal +5V, not +12V, up to 2 amps (for 10 watts total) but high power devices can be up to 5 amps at +12V /or +20V (for 60 to 80 watts total.)

    We would need to know the peak draw of the load you intend to hang on this to come up with reasonable recommendations for what to use for a boost converter (if it's needed at all). If the PV panel is marginal on how much power it delivers there may be no truly satisfactory solution. Designing even a 10 watt boost (or buck) converter powered by PV is not a totally trivial exercise if the power needs to be both clean & stable (which may or may not be the case.)

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