Connect with us

Noob Solar USB Circuit Help

Discussion in 'General Electronics Discussion' started by Jake., Jun 25, 2013.

Scroll to continue with content
  1. Jake.


    Jun 23, 2013
    This is my first circuit and I need help.
    My plan is to use a 5 volt solar panel, drop the power down and charge AA's, and step it up again to charge a USB.

    The diodes i'm using are "1N4001" diodes with the 0.5v voltage drop.
    The USB output is a step up regulator seen here:
    The USB output takes anything from 1v and amps it up to 5 volts (I Volt metered it and it works).

    After a good long charge on the AAs, I plug in the charger for my phone (or any other usb device) and it registers as charging, but looses power. Even when trying it in the sun.

    I think it has something to do with not enough current, so I also made (not seen in the picture) a input powered directly off of another usb with a couple diodes. My devices still say they are charging, but loose charge.

    I am a complete noob with this stuff, if anyone could help, that would be great. I already invested more than I wanted to with this project and I would like to make it work.

    If more info is needed, let me know.

    Thank you,
  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    Jan 21, 2010
    Well, that's going to give you about 1.8V to your USB. That's a lot less than 5V.

    Also there's not a lot preventing the AA cells from being overcharged (the three diodes in a row aren't going to do it)
  3. Jake.


    Jun 23, 2013
    the USB module I have amps up the volts to 5 volts. the link to it is included in the description.


    it would have been nice if you had supplied a clickable link, so I didnt have to type that whole flamin' thing in

    The AAs are rechargeable, any suggestion how to keep them from overcharging?

    Also, any ideas how to get the circuit working or do you think i need more current? if so how?
    Last edited by a moderator: Jun 25, 2013
  4. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    Jan 21, 2010
    OK, sorry, I misread what you were doing.

    What type of batteries do you have? You really need the appropriate chantrger for them.

    If you used Li cells (LiFePO4 are the safest) then you can probably connect a charger to the solar panel output. The 3.3 to 4.2V you get from them would be ideal to drive the module you have.

    In addition, you don't waste power with all those series diodes.

    Oh the diode before the USB module is not (or should not) be required.
  5. Jake.


    Jun 23, 2013
    I'm using AA NiMh cells. I'm not sure how safe those are but do I need a charge controller for those?

    If I were to get the batteries you suggested, would I need to get a separate charge controller or is it included with the battery?


    What do you think about this battery?

    If i'm right, I wouldn't need a special charger as long as 4.2 - 3.7 volts go into it?

    Thanks again
    Last edited: Jun 25, 2013
  6. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    Jan 21, 2010
    *ALL* batteries require a special charger! The only exception is for very slow trickle charging of lead acid batteries.

    For a LiIon battery, failing to provide the correct charging (and discharging) regime will result in a permanently dead battery at best and a very nasty fire with possible explosions at worst.

    In this case, you could probably get away with a cheap LiIon charger that plugs into a USB socket (there's bazillions available from China for a couple of bucks). Your Solar panel could probably plug straight into them, although I'd probably place a 5.6V zener diode across the solar panel to limit the maximum voltage.

    The charger will limit the current that can flow to the battery, so a few judiciously placed diodes would allow any excess current to pass to your USB module bypassing the batteries.
Ask a Question
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.
Electronics Point Logo
Continue to site
Quote of the day