Solar panel charger analysis with Ladyada

[Phillip Torrone], one of the original crew of HackaDay, now working with [LadyAda] tipped us off to this video of her explaining the device they built for configuring the charging circuits to be used with their solar panels. Unlike most of their tutorials, this one is not intended to be a final product sold on their store. Rather, this is a project that helps them deliver the best quality they can.

The unit itself is built around an Arduino and can log the statistics to an SD card, show battery voltage, panel voltage, and current from panel to charger. You can see in the video above how she uses this to refine her design in real time for optimal results.

24 thoughts on “Solar panel charger analysis with Ladyada

  1. It is not a project I have much interest in, but I love reading her writeups. The level of detail is excellent. It is nice to see how someone with more experience then I does things.

  2. @Whatnot

    Yes, the original charger let you adjust it up to 1000 mA by adding a resistor.

    I know this was really to cover the datalogger as an advert for the project case, but it still would’ve been interesting to see what the rest of the breadboard was doing.

    Presumably, altering that resistance to stay within the solar panel’s optimum range.

  3. I was really excited to see where this was going..and then the video ended. So what are we to take away from this? Some “analog electronics” is used to double the charging (?) current. Oh and there’s a nice box, too.

  4. Why did she go to the trouble of using an arduino instead of just etching a board? She was doing all of the additional circuitry, it seems counter-productive to use on of those things like that…

  5. @Jake the arduino wasn’t used to make a DMM, nor is it part of the charge controller, appears the plan is to have data logging that would require the arduino.

    @Matt MPP tracking, that was what I couldn’t dredge out of my memory to respond to the comment by Whatnot. This is a bit difficult to wrap ones mind around, but really does make sense when it hits home.

    Not sure where Adafruit/ Ladyada does her work, but clearly the “park” was a private residential or industrial are green spot, with AC units running. Glad I live where the only AC I hear is my own.

  6. So it logs/displays volts & amps, as well as being able to calc/view watts from the v&a?

    I’ve got a Metrix MTX3283 multimeter that can do that, with graphs, but the really interesting part of this, um, project is the MPPT (maximum power point tracking) she started to talk about with the extra breadboard, but then the video stopped and there’s no info on the linked url as to what she was doing with the extra breadboard. :(

  7. The first time I saw this project I notice same failure that I had during field try after developing mine solar charger.
    The failure is – too small solar panel, it gives less current than most phones want, so you cant use device when it. This limit functionality and situations where this charger can be use, for example you cant just sit in park and browse Internet on you phone without draining battery, so such charger useful only to campers on long trip who dont plan to use their phone much.
    Also it lose a lot of efficiency since it take much more power to charge battery instead of directly use this power

  8. I know it was kind of confusing. I think what she is doing is taking a 12 volt 2 watt solar panel and using a switching regulator (buck) to bring it down to 5 volts at 280 mA (about 1.4 watts). A good design tool is on the national semiconductor website called webench designer for switching regulators. Best you can get is about 90% or so efficiency on switchers and it looks like she is running about 70% with her circuit. I also think she was comparing the switching regulator to a linear regulator that has about 50% or less efficiency in this particular circuit. If you would like to design on webench try theses numbers Vin (min) = 5.5 Volts, Vin (max) = 15 Volts, Vout = 5 Volts, I out = .3 Amps, Temp 30 DEG C. Turn the webench optimizer up to 98% efficiency and you will get some nice circuit designs. The one that uses the LM21305 looks like a good candidate with about 89% efficiency at $3.55. The nice thing with national is the give you a great BOM and in some cases they can actually kit the circuit. And for the newbies out there check out EEVBLOG#90 “Linear and LDO regulators and Switch Mode Power Supply Tutorial” Dave gives a great explanation on switchers, LDOs and linear regulators. Later Mr. J

  9. yea the arduino is kinda piggy with its current consumption in stock form

    you can dick with it and get it into ultra low modes, but thats just the chip, the regulator burns off a lot of heat

    I like arduino, I try to be a helpful member of the community, but yea, its overkill, its a clunky software based datalogger, and the arduino language is as about as efficient as the banning system employed here

    if the arduino is an important part of this project, and you know absolutely nothing of real micro-controller development,you could still use a attiny84 with arduino code at less than 2v and 1mhz and still get correct data

    crap read her article about avr dude, anyone who is not a total dolt can figure it out in less than 10 min by selectivity scan reading (I know I did)

  10. It’s possible with passive components and a single IC to handle direct solar output, but it’s still not reliable in most environments.

    You could do a successful startup off intelligent portable solar solutions, nobody has yet and there is plenty of profit because of cheap manufacturing.

  11. I have wondered for years why there are not better solar charging systems. There are several successful solar panel companies that sell to everyone from the military to the eco-geeks but their solar charging offerings are still pretty sad. Many don’t even have a charge controller; just a diode to prevent reverse current.

    I think something that could be tuned for a particular cell and automagically optimises charging for available light would be really popular especially in the out of doors crowd. I would buy one.

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