2) Will the ultracaps negatively affect in any way how the panels charge devices when there is ample solar input?

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1 Solar USB Charger Posted by Joshb /07/09 12:16 Hi! I'm Josh Brown, 26, from Hampton Roads, Virginia. I went on and bought (10).47 Farad ultracapacitors($1.49/pc), (20).5v 200mA solar cells($.50/pc), some 7805 voltage regulators ($.39/pc) that put out v and up to 1A when properly sinked and a few other things (diodes, switches, ect.) I gotta have at least 7 volts for the 7805 to do it's thing so that should use up about 14 cells in series). I plan to wire the capacitors in parallel (they are 5.5v so I just want to multiply the energy capacity) and charge the caps with the solar cells. I also plan to wire in a diode so the caps won't bleed back into the regulator/solar cells and I'm going to wire in a female USB connection to charge USB charged devices from. I might need more ultracaps in the end but I needed to start somewhere. The devices that I want to charge pull less than 500mA (max USB spec) and most pull less than 150mA. Any help/input would be GREATLY appreciated. I recently got laid off, college and this project are my boredom fighters. I'm also an avid photographer so I'll will highly document this project with pictures. A few questions: 1) What formula can I use to compute how long a 5v 150mA device can charge from 4.7F of ultracaps when fully charged and no sun input? 2) Will the ultracaps negatively affect in any way how the panels charge devices when there is ample solar input? 2) How will a 14v 200mA solar panel react when a device wants to pull more than 200mA, will the solar panel heat up like transformers do? (the 7805 voltage regulator can handle up to 1A when sinked) More questions to come as these products arrive and I start to play! ;) Posted by Michael C /07/14 13:15 Hi Josh, Welcome to this site. I work with solar power (and Ultra caps) so I can answer some of your questions. The last question 2) ( 3? ) is easy. The solar panel will not heat up from current flow. The sun WILL heat the panel. The panel will only give what it can - the device will be a little starved for power. If your device takes that much power, the solar panel may not be able to run it. The rating on the solar panel is only a guide. You may not have as much sun or the angle of the panel to the sun is off. In both cases you get less then "test" spec for your panel. You could test your device by connecting it to the solar panel, place the panel in the sun and start the device. If it runs - you are set. Last point, you may not be able to run a device and recharge Ultra caps at the same time. 2) ( 2? ) If the ultra caps have a lower voltage, they will drag the voltage down like a regular rechargeable battery. Once charged fully - the current will go somewhere else - like into your device. So, if the ultra caps need charging then there is less for your device. They work the other way too, they will discharge (into your device) to compensate for a cloudy solar panel. 1) (1?) You need to convert Farads to Amp hours (milli Amp hours) to give you something that you can use. This formula should help: (Vmin + Vmax)/2 * F / 3600 = Ah Vmin & Vmax - upper and lower voltage. This is the voltage range that your device has to work in. Vmin is the voltage that your device dies at, my GPS stops at 2 volts. F - Farads coulomb, a unit of electrical measure. Ah - Amp hours (/1000 = mah)

2 So, (4.5V + 5.5V) /2 * 4.7F / 3600 = Ah 5 * 4.7F / 3600 = 6.53ma You have 6.5 mah in Ultra caps. Also, remember that you are charging a battery inside the device which takes more then 150ma. If the device lasts 4 hours then you have 150 * 4 = mah battery to charge. Running the problem backward: 0.7Ah * 3600 / 5 = 504F You need about 500 Farads in caps to charge one device. Hope this helps... Posted by Joshb /07/14 15:51 Thank you for all the valuable information Michael, you're like an electrical encyclopedia! I have twenty 200mA solar cells arriving any day now. Wiring them in series should give me roughly 10 volts and 200mA in perfect conditions right? I could order another 20 and wire the two sets in parallel to get 10v and 400mA. I was planning on using a 5v voltage regulator to take the voltage (70% output at 7v to 100% at 10v) to where I needed it for USB spec power 4.75v-5.25v. Do you think a cloudy day would give at least 70% output from the panel? From what you said, it sounds like I'd be better off charging some batteries if I want to stay portable. My main motive is to charge a device with solar power and if all my devices are charged, then the internal power storage saves the solar power for charging when not in the sun. There are products on the market that do this but they don't have enough solar output, making them take too long. I can construct the higher powered panels much more cheaply myself considering I only need 5 volts max and 500mA max. I guess the main question is what is the most efficient way to do this? I've also considered designing some fresnel lenses to concentrate the light and improve the panel output. Posted by Joshb /07/14 19:40 Oh I just had another thought...what if I wire the 20 cells for 5v and 400mA (2P of 5S) and use the caps for when the voltage output drops below 4.75? 4.75 isn't necessarily the Vmin of the device but is the Vmin of USB-spec. If I do that, then when the caps are charged, the device will start charging (letting me know the caps are full) and if a cloud drops in the way it will charge hopefully till the sky clears again pulling what it needs from the caps, but not solely from the caps. (I need to take more electrical engineering courses next year ;) ) Posted by Michael C /07/15 14:25 Josh, I was thinking more like "info clearing house". Yes, You will get that much 200ma) from the solar cells. On your question of cloudy solar, I like the explanation of Home Power magazine. If it is hazy out you get between 70-95%, for light clouds 50-70%, for overcast skies 25-50% and heavy clouding 5-30%. If it is raining, your panels will just get clean. Of course, the skies can be sunny and rainy at the same time - go figure.

3 On the "concentrator lens" - I would not do it. The solar panels that you get are not designed for high heat conditions. In a short time the Silicon will degrade OR the solder connections may fail OR the plastic cover on the solar cells will turn opaque. I made a solar panel (DIY - Ultra Cap Battery - Part 1) that is made from 6 thin film solar panels. It is very portable (folds) and it powers the size of cap Battery that you are looking at for USB stuff. The thin film panels work well in cloudy weather too. Each one of those puts out 3.6-4V at 150ma. Six of them collect about 900ma (just shy of an amp) in sun light. Look up (web) "Big Frog Mountain" for these film panels. There are higher voltage solar panels too. Besides, you would just have a bulkier system with lenses fixed on some frame work to focus light. If I were going to do (USB charger) it, I would get the solar cells like you are (50 cents each- good deal) doing. I might buy enough for 6V at ma. I would use 2X F 2.7V caps which will store enough power to charge things. I would box the caps just like the Cap Battery that I made. I would use an "Any Volt Micro" (runs on V) for the final output (USB-5V) so I do not have to rely on a meter. The "Any Volt Micro" would save me from needing different (7V, 10V???) voltages. Just like my original cap battery - I would add switches (including one to cut power to the voltage regulator) and jacks - USB and the "N" size jack (external solar/ gen set charging) for running straight off the caps. My cap packs will work now. I would only need a cable with the voltage regulator to connect my caps to a USB connector. Hope this helps some more. Ps. As for the School courses, I would not bother so much. In 2 years (approx.) the only skills you will need are for Farming. Why? Because "Peak Oil" will sideline any plans you might have. Imagine that your civilization runs on only one power source - oil. Now, what would happen to that civilization if the oil ran out? You are in that world right now LATOC Posted by Joshb /07/16 19:55 I checked out the AnyVolt Micro when I started reading your other posts (before I joined ultracapacitors.org) and the datasheet says it's 73-77% efficient...which doesn't sound too appetizing when figuring that solar is already very inefficient. There's got to be another dc-dc converter that doesn't cost 20 bucks and is a bit more efficient. Those film solar cells are quite interesting though. Amorphous silicon does well in cloudy conditions as well, I assume thats what these thin film cells are. I bought a 5 dollar 12v to USB adapter from a hardware store. I think I might be able to rob some parts from it for the DC-DC conversion, maybe I can solder in the caps in between the converter and the panels along with a diode, I will report back on it. The solar cells and caps are due to arrive on July 23 (electronic goldmine is SLOW!) Posted by Antonm /11/15 00:02 BTW., your link doesn't work... Posted by Antonm /11/15 00:12 I would welcome an update on your project. Did you find a better Boost/buck converter than the Any Volt Micro? I may put together something in this vein too, as I have two MP3 players that charge from a mini USB cable. I have an extra USB to Mini cable to sacrifice. The regulator will be the hub piece that eventually I'll add a panel and ultra-cap pack. But first I'll make a NiMH battery pack.

4 Posted by suely /12/02 20:53 Antonm,you are great to use ultracapacitor in series in your USB charger. i am interested in with your USB,and which ultracapacitors you will be choose? You can to me. Thanks, Suely suelydong@yahoo.com Posted by danielhenry /06/29 03:02 The market products that do this, but do not have enough solar power in order to take too long. I can build a top panel fueled much cheaper considering I only have 5 volts and max 500 ma max. I think the most important question is, what is the most effective way to do this? Are also considered during the design of some of the Fresnel lens to focus light and improve the return on the panel. Posted by Michael C /07/10 19:15 The question really is which type of panel to use? If it has to be attached then mono or multi crystal silicon. If it can be "corded" then get thin film panels at 6 volts. You can get more than one panel on a cord. Posted by dwaynejenkins /07/06 03:06 If I need anything can you give me a link to how it looks like? I have a lot of electronic stuff but im new with hardware tinkering so i might have it laying around but might not recognize it Posted by Michael C /07/13 17:33 Sure, just describe or picture it here. I'll see if it is familiar... Posted by greenrvliving /08/03 12:26 Thank you for giving information.no harm in using solar usb charger.i also want to use USB charger.

5 Posted by greenrvliving /08/03 12:30 I don't have much idea about the type of panel. Solar energy is a conventional source of energy also eco-friendly. Or at least, it can be everywhere if you have the right solar panels to catch, store and use it Posted by MichelleVivera /09/05 00:36 I'm not sure how long it would keep the DR powered for, but this might be a good soulution. Solar Panels Posted by ShelbyBoaro /02/09 08:41 I have been looking at a few and thought it would be nice to have a good sounding radio that has solar and hand cranking power options. Mobile Crane Portable crane Mobile Cranes