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Step 7: Enjoy

That was easy. I've done this a couple of times before and at this point building one takes me under 20 minutes.

So the breakdown is this.

Cost: $4

$1 Tupperware
$2 Solar Panels
$1 Battery holder
$0.02 Blocking Diode

Time: 20 minutes.

You can use this EXACT same setup to power little light up projects. Throw in a few transistors and resistors and you can make a dark detecting circuit for all of $0.20 more.

If you're looking for solar panels or little solar kits I have several available on my website browndoggadgets.com.

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<p>I have been struggling with this forever. All I want to do is use my 5v panel to charge my 1.5v NiHM triple A batteries. Seems like it kills every battery, they start out low at 1.0V and then after I use the panel with + to + - to -, with a diode on the negative lead.</p><p><br>What am I doing wrong?</p>
<p>First of all, the blocking diode usually goes on the positive terminal of the solar panel going towards the batteries. Secondly, you are using multiple batteries correct? I completely disagree with this article, if you have a 4.5v panel you need to have 3 batteries connected in series to charge safely since each battery is 1.35v charged. With only two batteries on a 4.5v panel you are putting too much voltage on the batteries 4.5v on 2.6v max of batteries, and risk damaging them, especially long term. Over voltage destroys batteries. This is why most solar lights have 1.5v, or if they use two batteries 3v, panels.</p>
<p>Sorry I missed that you have a 5v panel. In this case you may want to use either 4 batteries (which would never get fully charged but would come pretty close at 1.25v) or else consider using a resistor with at least 2 batteries. Remember R=V/I from physics? If you need a refresher see this page here: http://www.gtsparkplugs.com/Dropping_Resistor_Calc.html You do need to be careful though since the more voltage you are dropping, the higher the wattage resistor you need (in general, most resistors are 1/4 of a watt. For one battery ideally shoot for a voltage of 1.5, 3v for 2 batteries, 4.5 for 3 6 for 4, and so on.</p>
<p>Ok, also if I stepped the volts from 4v5. to 3.6 v to charge 2 batts or something like that, could I get more mA current, charging the battery faster?</p>
Ok, I have a 4.5V Panel at 200mA, about 1W, and I only had 2 NiMH triple A's connected for charging. <br><br>I realized I did the diode on the wrong side, but was confused because I guess the Positive side of the battery actually has the most Negatively charged particles (sigh..lol) so everything I read prior about current flow direction was misleading to the project.<br><br>Soo, I set the diode on the pos terminal of the panel facing toward the battery pack (I guess about 2.5-2.7v) and It didn't die, but didn't seem to charge after a couple hours in the sun.<br><br>Is there a way to directly check if the current is flowing into the batterie's + terminal?
<p>I would first make sure that you have the diode the right way round. Diodes do obviously only go in one direction and have a set polarity. The line on the diode always indicates the negative (out) end. </p><p>The easiest way to check is to put a multimeter, set to the ma current range and then connect it in series between the diode and the battery pack with the red positive probe on the diode out side and the black negative probe going to the battery pack. The meter will read a positive reading in mA if everything is working correctly, which is how much power is flowing into the batteries. If you don't have a multimeter I would highly suggest getting one as it's really an essential tool and worth it just for checking batteries and basic repair/automotive uses; For basic dc, low voltage, use, they can be found quite cheaply at around $7 (I can recommend some if you don't have one). You can also short circuit the solar panel through a multimeter with just the diode and nothing else attached to it to get an idea of it's performance. Solar panels are one of the few things it's fine to short circuit. Unfortunately apart from a multimeter the only thing I can suggest is connecting an LED temporarily in series before the battery packs just to see if the panel is producing power (though if you leave the LED in it will burn out without a properly sized resistor).</p><p>The other thing to keep in mind is that solar panels in general, although especially these smaller ones, are very sensitive to the angle of the sun and the output can go from maybe 100mA or possibly less laying flat on the ground to 200mA angled into the sun. This site has lots of detail on solar panel angles (and the effect on output) and was very helpful to me: <a href="http://www.solarpaneltilt.com/" rel="nofollow">http://www.solarpaneltilt.com/<br></a></p>
where's the best place to find the solar panels? I'm sorry if someone asked this and I didn't see it when I looked
<p>Hi,</p><p>Great idea, but your $4 build figure doesn't add up.</p><p>On your website you are selling the..1V 500mA Solar Cells for $8.99!!..so how can you build it for $4?</p><p>Sorry I dont mean to be negative, but this fact appears to have been &quot;over looked&quot;</p><p>I look forward to your comments.</p><p>Regards</p>
What I did was got 2 little solor toys from the dollar store and hacked off the panels
<p>Yep me too</p>
<p>Hi,</p><p>Nice build you made! I want to make my own now aswell. I have a question, what will happen if there is no battery hooked up? Will this destroy the cells?</p>
<p>How would I hook up a battery and a charge, like the pump with panel with battery below? Should I put a diode at the solare panel and a zener diode towards the battery? </p><p><a href="http://www.amazon.co.uk/gp/product/B007IS4B4S/ref=s9_dcbhz_bw_g86_i3_sh" rel="nofollow">http://www.amazon.co.uk/gp/product/B007IS4B4S/ref=...</a></p>
Could a charge controller be placed somewhere between the solar panels and the batteries? And can the batteries be charged while they are also powering a small device?
<p>In theory, you have the right idea, however as these solar panels product such a small amount of current.voltage, I am not sure if it would be worth it.</p><p>If you had a larger panel producing more power, say a 12v / 2.5W+ then you could connect this to acharge controller and car battery/inverter setup... </p>
<p>Hi,</p><p>Great idea, but your $4 build figure doesn't add up.</p><p>On your website you are selling the..1V 500mA Solar Cells for $8.99!!..so how can you build it for $4?</p><p>Sorry I dont mean to be negative, but this fact appears to have been &quot;over looked&quot;</p><p>I look forward to your comments.</p><p>Regards</p>
<p>Works very well.</p><p>Thanks.&lt;img src=&quot;http://s04.flagcounter.com/mini/kfoW/bg_FFFFFF/txt_DEDEDE/border_F7F7F7/flags_1.jpg&quot; style=&quot;display:none&quot;&gt;</p>
Great idea, you mentioned the dark detecting circuit, how would you work that in? It would be perfect for some Halloween led &quot;eyes&quot; i built a few years back.<br>Thanks again
<p>Nice job !!</p><p>But I have question, do we really need the blocking diode? </p><p>As far as I know, solar panels have almost the same physical structure with diodes and they don't allow back current.</p><p>Could you correct me please</p><p>Thanks</p>
<p>Solar panels do allow back current.</p>
<p>What would be required to run a laptop computer?</p>
<p>You would need a much bigger solar panel (~15v and at least 60 watts) and good size car battery plus a 12v DC to AC 120v inverter, to plug in your AC laptop adapter.</p>
Will a small led work as a blocking diode ?
<p>yes</p>
<p>so simple</p>
<p>Very nice project, could have made it very smaller and thus more portable/convenient. Great make overall, hopefully make my own in the next few days/weeks.</p>
<p>Hey boys and girls, here's a source for some cheap solar battery chargers. Used solar powered yard lights. These ARE solar powered battery chargers already along with a circuit to turn the light on when it's dark. Folks toss these things when they stop working. Usually it's the battery that dies or corrosion that causes the failure. Many end up at your local 2nd hand store. Maybe 50 cents or less for each one. Insert a new battery and/or clean up the contacts and pull out the LED bulb you're done. They're inexpensive when new too. $2 - 4 bucks each. </p>
Hey, kids. Here are some electricity basics. mAh (milliAmpere-hour), a unit of charge and mA (milliAmpere), a unit of current (charge per unit time) are not the same thing. A 3000 mAh battery would run, in principle, for 30 hours if a constant current of 100 mA is drawn from it, for example.
I can't get over this charger, it's just &quot;different&quot; from the others, this is what got me wanting to make one, so whenever I pass by this when looking for a good design (which I'll probably just end up making my own), I just always click on it and look at it again and just see how simple it really is<br><br>P.S. My Algebra teacher in 8th grade had a last name of Zimmerman, so I always think of him when I see yours
mpeterson19, I can't tell if you mean on/off switch or have the electricity go one way? If your talking about direction then use a diode inbetween the panel and the circuitry (so it goes panel, wire, diode, wire, circuit stuff). If you're talking about on/off switch for charging then you would put an on/off switch between circuit and output or between panel circuit (in order)
Where did you get the solar panels from?
AndroidJack... it's the mA... the panel's mA shouldn't exceed 10% of the mA capacity of the battery...(theoretically)... the panel usual doesn't get what it says when it comes to mA so you have a little wiggle room.
Awesome build! <br> <br>This really got me thinking, so I visited browndoggadgets.com for even more ideas. I have two 5V 100mA solar panels already that I want to use, but my question is what determines the rate at which the batteries charge? Is it the difference between the mA from the panels and the mA capacity of the batteries, is it something to do with the voltage, or is it a combination of both, and if so how exactly?
Great Instructable. <br> <br>Just wondering how much the voltage of the solar cells matters? You went into depth about the amps, but only mentioned that your cells run at 4v. <br>Does the voltage need to be higher than the battery supply? <br> <br>Also what happens if you do leave them to charge for months? I have some ideas for projects, but they would be sitting outside for a long time...
Yes, the charge voltage must exceed the total full-charge voltage of the batteries. <br> <br>As long as you have your diode properly in place, keeping this setup out for a few weeks should be ok, but months may be pushing it, as the batteries are being charged and charged and charged without any usage save for leakage. In your case, this sounds unavoidable, so you may want to look into batteries that are built for this kind of duress, or even consider some type of device that switches off the solar panels when the batteries reach full capacity, and then on again when they become low.
On my battery clip I have a toggle switch. When I have the solar panel charging the batteries, do I leave the switch on or off?
Depends on where the switch is located. If it is switching between the panels and the batteries, then leave it closed (on) so that the panels may charge the batteries. If it is after the batteries, then it really doesn't matter, unless there is a device plugged into the USB. In that case, close the switch to charge the device, and open it to prevent the device from charging. Are you using the switch INSTEAD of a diode? If that is the case, keep the switch closed only when you know the panels can harness sunlight.
Is it okay if I want to hook my two 4.5v 80mAs in a series for just two batteries, to make it more powerful?
I am doing some research that requires about 300 AA batteries in a village with no electricity. I want to use the eneloop 2000 as it seems like they will last a long time and also recharge a lot of times. I decided to make solar chargers because $30 each for 30 chargers ON TOP of the battery costs is tough. I'll be right near the equator so sun isn't an issue. Been reading what I can, but what would you EXPERTS recommend to charge 4 AA batteries in about 8 hours? I'm guessing over 6V panel but what ma? I'm thinking of training women to make these little chargers for batteries and cellphones so trying to figure out how to solder without electricity. MAYBE can use butane if I can find a can in the city to recharge the cartridge. I leave in less than three weeks so any help would be appreciated.
For soldering u can use any kine of metal with sharp tip... Heated with any kind of heat source, fire from wood chips would work, nor biogas, kerosene stove, alcohol burner and many more....
You can find solder guns that use gas to burn. I have one. They are portable and use lighter fluid. You can find them on ebay pretty cheap.
You can get some that you actually put a lighter in. Thats a lot easier than trying to find lighter fluid

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Bio: I used to teach middle school science, but now I run my own online educational science website. I spend my days designing new projects for ... More »
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