solar to power mintyboost?

by MTXRooster on Mon Oct 01, 2012 11:02 am

My question is generally similar to a post located here: viewtopic.php?f=15&t=19515&start=0 (about powering mb with 6vdc)
Recently I read a post elsewhere about using solar panels to power a usb port to charge various devices. I have an assortment of panels, ranging from tiny 1.x volt panels about 1 in. squared to a full sized, 6/12v 53w "home/commercial" grade panel.

I'm trying to use them (live in a really sunny state) to save a little and put the solar energy to good use, but don't have the funds to "go big", and actually make a deep cycle battery "proper" system. I read an article recently about using the mintyboost as a vessel between the panel and "device". My main concern is this..

The article used a 6v panel, and led mention that you could alternatively use a cluster of small panels (such as the 1in ones from those solar night lights you put along your path, driveway, etc.). When I started digging around though, I find warnings and notices all over saying NOT to ever use more than 5v with the mintyboost. The article I linked (also on this forum) even mentions an elaborate schematic someone was working on to allow the 6v source, though gets lost in a debate over battery vs. capacitors..

Can someone give me a decisive "this will or will not work" with a 6v source? Some research seemed to indicate I need a "Buck converter", not "Boost convertor", but when I looked up buck converters, they were all these large mammoth devices, where people are taking far more excessive amounts of voltage and desiring low voltages.. Didn't seem to really fit what I need, but by the same token, there are a ton of posts/comments here and on other articles in regard to using a mintyboost NEVER to exceed 5v.

As a follow up item. Whether I provide an exact 4.8-5v or less (or more, like the 6v I am mentioning above), is there a "easy" way to get 1000ma out of this instead of the 500ma? I ask because while I see the HTC Evo listed (one of the many things I plan on using this for), the Evo actually prefers to draw 1000ma, and in fact, on car chargers rated at 500ma causes the battery/phone to overheat as well as heats up (excessively) the car charger. The stock supply ac adapter in fact is rated at 1000ma. I'd like to replicate that, if possible, but know next to nothing to make it happen. I can solder and build for days though, if I have something to follow, rofl :)

Appreciate all the time and assistance on this, thanks :)

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Re: solar to power mintyboost?

by adafruit_support_bill on Mon Oct 01, 2012 5:21 pm

Solar power is not steady power and it typically paired with batteries for that reason. The output voltage also tends to collapse if it is overloaded, so a solar-specific charger circuit is required for efficient charging.

See the "Solar Minty Boost" in this tutorial: http://learn.adafruit.com/usb-dc-and-solar-lipoly-charger
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Re: solar to power mintyboost?

by MTXRooster on Tue Oct 02, 2012 1:07 pm

How does that devices load circut work exactly.. I live near Phoenix, Az., we have direct non-stop sun almost from sun-up to sun-down. While I've never experienced an issue powering stuff, I won't argue with ya, but I'm wondering if I'm going to end up killing a battery or something, either from it never getting fully charged, or un-nessarily being depleated on a daily basis where it doesn't need to be.
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Re: solar to power mintyboost?

by adafruit_support_bill on Tue Oct 02, 2012 1:34 pm

You are lucky to live in one of the most solar-friendly locations in the world. But you still have to worry about the decreased solar output at dawn & dusk. When the solar output decreases to the level of the load, the voltage will drop suddenly. If this output is directly driving the MintyBoost with no battery as a buffer, the Mintyboost output will drop suddenly too. The charging logic in may smartphones and similar devices does not handle this condition well. Some will start discharging back through the Mintyboost - quickly draining the smartphone battery.

The Design Notes section of the tutorial describes the theory of operation: http://learn.adafruit.com/usb-dc-and-solar-lipoly-charger/design-notes
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Re: solar to power mintyboost?

by ffair on Fri Nov 22, 2013 8:03 pm

Sort of along these lines, I think I may have overloaded my LiPoly chip. Is there a bit/resistor/ something that can be replaced, or is the chip likely damaged beyond repair?
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Re: solar to power mintyboost?

by adafruit_support_bill on Fri Nov 22, 2013 8:52 pm

@ffair - Have you connected in a way that you think might have overloaded it? What are the symptoms that make you suspect it has been overloaded?

Some kinds of damage may be repairable, but we need to know what we are looking for.
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