I need some solar help.

Ok so i dont know a whole lot about solar but i love the stuff. I also dont have alot of money (byproduct of not having a job) and wanted to make my own solar stuff for cheep. I posed another question about this but it was poorly writen so im putting more time into this one. I bought 9 solar powerd garden lights from dollar tree and one car phone charger. Now ive been led to belive that if i take a 9V battery and hook it up to that car phone charger it can deliver a safe and efficent charge to charge my phone. However since i dont want to spend a ton of money on batteries i deside to turn the consept solar. Ive found a few bumps along the way so if you have any advise please share it. 
1. First ive been told that you need to connect a solar pannal to a load (for example a motor) to get an acccurate reading on your multimeter about the panals output voltage. Is this true?
2. I measured one of the solar pannals with a load in the sun and was told the cell emitted 1.5 volts. I then put five of them in serize and only got of reading of 2 volts not the 7.5 i was expecting.
3. I dont understand the imprtance of diodes when it comes to solar projects but as far as i know their just a safety procaution to help protect your cells against damage. Is this true and if so can i make my project work without them.
4. I dont know how to messure the amprage on my multimeter. Do i need a knew device or am i just missing something.
 Thank you so much for takeing the time to help me out with this.

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-max-5 months ago
2. I measured one of the solar pannals with a load in the sun and was told the cell emitted 1.5 volts. I then put five of them in serize and only got of reading of 2 volts not the 7.5 i was expecting.

OK, you are headed the right way! You need to size your load appropriately to the solar cell(s) you are using:

If you think about the power your panel produces, it produces NOTHING if you don't connect anything, right? and if you short-circuit the output, then again, you get NOTHING.

In the first case, the panels give a pretty high voltage reading, but that is because there is no load and as such the voltage naturally rises to some maximum value. lots of volts * 0 amps = No power!

In the second case, you shorted the output, so the panels are delivering as much current as they possibly can, but alias, no voltage is produced by definition of a short circuit. lots of amps * 0 volts = No power!

Now, as you can probably imagine, there is a special "goldilocks" zone where the voltage provided and current delivered collectively give the most power! This is known as the Maximum Power Point (MPP). There are special types of DC to DC converters, called Maximum Power Point Trackers (MPPTs) that have advanced circuitry inside that attempt to constantly track the MPP to charge batteries as fast as possible. Good ones are expensive and for small hobby projects, not necessary. Just try and size your solar bank appropriately to the load, that's close enough.

-max-5 months ago
4. I dont know how to messure the amprage on my multimeter. Do i need a knew device or am i just missing something.

Just set your multimeter to the "Amps" or "milliamps" range, and you might need to move the red lead over to the fused current jack. Then just measure away! Be careful though, and never connect the ammeter directly across any device that can supply lots of current, because that's how you blow it up.

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If your current multimeter does not have a current range, then you should not even be using it, as it is likely a very special type of meter (like a vintage analog voltmeter) or just a worthless piece of sh*t, most likely the ladder. I recommend this one as it's pretty accurate / precise, very cheap for what it offers. I also recommend getting a cheaper model along with it so you have 2 decent meters so you can voltage and current.

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If you absolutely cannot possibly afford something that costs less than a good dinner out, and will last you a lifetime with good care, then you can just get a current shunt resistor (a one ohm resistor or smaller), measure its exact resistance and note it, and then pass the "Current-under-test" through it while measuring the voltage drop across it to calculate the current that way.

-max-5 months ago
3. I dont understand the imprtance of diodes when it comes to solar projects but as far as i know their just a safety procaution to help protect your cells against damage. Is this true and if so can i make my project work without them.

"Diodes" can actually serve several purposes in solar applications. In the case of "protection," I assume you are referring to connecting a solar cell directly to a battery to charge it. The diode prevents the battery from discharging back into the solar cell when no light is available.

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If you want to connect a whole bunch of cells in series, then it's common to have a diode across each individual cell (in reverse, of course) so that if that particular cell gets shaded by a leaf or something and it stops producing voltage/current/power, than the current the rest of the string is generating still has an electrical path to follow. Let me explain:

Suppose you have 12 cells in series: Each generates 1V @ 100mA under the sun, for a total of 12V @ 100mA. Great! about 1.2W is being generated. But what happens if you shade just a single panel? You would think that this is a proportional drop in power, with 11 cells still getting light, and the shaded one getting maybe half light, so 1/24th less power, maybe 1.15W?? well WRONG WRONG WRONG!!! If even just one cell gets half-shaded on, then that V-I curve drops/changes, and now with the shade, it can't even produce 100mA short circuit!!!! Let alone produce any power at that current! The other cells are still trying to push 100mA through it, but that damned shaded panel is now not only not producing any power, it's actually acting as a resistor and draining power from the rest of the series! The panel might have something like -2V across it, so now with only a ~5% loss in light, we have lost like 25% of the power! Worst of all, forcing a current through the cell might damage it, particularly in larger solar arrangements. By having a reverse-diode across each cell, it prevents any cell from becoming a hindrance to the series rather than a help. This helps somewhat in preventing massive power losses by small amounts of shade in the "worst places".

-max-5 months ago
1. First ive been told that you need to connect a solar pannal to a load (for example a motor) to get an acccurate reading on your multimeter about the panals output voltage. Is this true?

Solar panels typically have a couple of common voltage ratings:

* Vopen: the open circuit voltage: this is mostly useless because this is under no load. Like a car revving it's engine in neutral.

* Vpmax (voltage at the maximum power point). This is the "ideal" voltage output of the solar panel, and is the point at which the voltage * current = the most power! You need to have a just the right amount of load connected to the panel to ensure it operates at this maximum power-point. Hopefully you can see the picture I pasted below:

http://solarprofessional.com/sites/default/files/a...

-max-5 months ago
1. First ive been told that you need to connect a solar pannal to a load (for example a motor) to get an acccurate reading on your multimeter about the panals output voltage. Is this true?

Solar panels typically have a couple of common voltage ratings:

* Vopen: the open circuit voltage: this is mostly useless because this is under no load. Like a car revving it's engine in neutral.

* Vpmax (voltage at the maximum power point). This is the "ideal" voltage output of the solar panel, and is the point at which the voltage * current = the most power! You need to have a just the right amount of load connected to the panel to ensure it operates at this maximum power-point. Hopefully you can see the picture I pasted below:

Jack A Lopez5 months ago

I guess this is a 4-part question. So here's a 4-part answer:

1. Electric power is the product of voltage and current: P=V*I

For a device to do anything useful,it needs a little bit of both voltage and current.

The Wikipedia article for "Electrical Load",

https://en.wikipedia.org/wiki/Electrical_load

I think is sort of a good introductory explanation as to why the voltage of a voltage source will change as it is loaded, i.e. as current is drawn from it.

For a story more specific to solar cells, look for a site that explains the I-V curve (current-voltage curve) typical to solar cells. I found this one:

http://www.pveducation.org/pvcdrom/open-circuit-vo...

By asking Google(r) Images to show me "solar cell i-v curve".

2. I expect the no-load voltage (meaning measured with just the voltmeter) of 5 panels wired in series, to be approximately 5 times the no-load voltage of a single panel. I am guessing you have some of them wired backwards, or you have some large differences in illumination, like a shadow falling on half of them.

3. All you need is a single diode, placed in series with your series string of 5, or N equals however many, panels. It is important because the voltage across the panels depends strongly on how much light shines on them. (Duh! 'Cause they're solar panels, amirite?) Also the amount of light can vary wildly, e.g. a shadow from a cloud, or something else, covers the panels, and instantly the array of panels has a voltage less than the battery voltage. As a consequence of this, the batteries will try to push current backwards through the panels. Aside from the possibility of damaging the panels, this is condition where the battery is losing energy rather than gaining it, and the whole point of this game is to move energy from the panels into the battery, not the other way around. So do not omit the diode. It is important.

4. To measure current with a multimeter, the meter must be set in ammeter mode, AND, it must be placed in series with the load. This page has some pictures and explanation,

https://www.allaboutcircuits.com/textbook/experime...

I found the link above by asking Google(r) Images to show me "ammeter how to measure current".

Notice that the multimeter often has a separate jack for measuring current, meaning you have to unplug one of the leads and move it to a different jack.

Also note that the meter is essentially a short, like a piece of wire, when configured as an ammeter.

By the way: Do not forget that your meter is configured this way, as a short, as an ammeter, and then try to use it later as a voltmeter; e.g. by putting it across a battery and shorting the battery, and maybe over-currenting the meter. It is kind of an easy mistake to make.

Another way to measure current is to include a small resistor (small compared to the load) in series with the load, and then measure the voltage across that resistor. For example if that small resistor is a 1 ohm resistor, and you measure 50 mV across it, that means there is 50 mA flowing through it, by virtue of Ohm's law: V=I*R

inconceivable1 (author)  Jack A Lopez5 months ago

ok this was also pretty helpful

1. i did make sure each cell was configured the right way( unless the black and wihite wires were worng.

2. if i wired 3 cell in parrell and put a diode between the them and the battery they charged and then replicted thi 3 times would that be an effectave way to charge 3 AAA batterys?

It turns out I have some of these solar light gizmos, and I think they are the same as the ones you have. I got 'em from the local DollarTree(r), and they even have the same color wires (black and white) on the inside, and a single AAA Ni-Cd cell, and a holder for it, and everything.

So I am just going to take three of these apart, and rewire them the way you suggest, for to charge the 3 AAA cells that came with, with the addition of a single diode, and also a 1 ohm resistor, for to measure the charging current.

This will probably take a few hours, or days, depending on how distracted I get by other things I am working on or playing with.

While you are waiting, please ask Google(r) to tell you about "YX8018 solar light".

https://www.google.com/?q=yx8018+solar+light

It is the name of the IC. You see, a bunch of people have already taken this gizmo apart, and written pages about it. Also it looked like there was Youtube video in these results too. I have not watched it yet.

Also that link is for anyone else reading this thread, who wants to know more about the specifics of this particular dollar-store-solar-light thing.

OK. I took apart three of those solar light gizmos, and I added some little stubs of solid 24 AWG copper wire to the panels and to the batter holders, so I could plug them into a little proto-breadboard thing I've got.

The reason I did things this way, was so it would be easy to re-arrange things, so that I could try both, battery cells in series plus solar cells in series, and, battery cells in parallel plus solar cells in parallel.

The other two components you will see on the breadboard, are a common silicon diode (1N4007), and a 1 ohm (brown-black-gold-gold, 1/4 watt?) resistor.

The resistor is just there for current sensing; i.e. I measure the voltage across that resistor, and I assume the current flowing through it is I=V/R, and the math for that is easy because I am dividing by one. In the pictures, my meter is measuring millivolts (mV). Dividing by 1 ohm, gives that same number, only in milliamperes (mA) of current.

I am kind of ignoring the fact that my resistor is not precisely 1 ohm. Last stripe gold means 5 percent tolerance. So the numbers you see on the meter are imprecise, by about %5, not including the (hopefully small) error introduced by the meter itself.

Anyway, the first pic is everything wired in series.

The second pic is a parallel group of 3 solar cells, in series with diode, in series with 1 ohm resistor, in series with parallel group of 3 batteries.

I kind of think the series arrangement is putting more power into the batteries; i.e. (30 mA)*(3.6 V) = 108 mW versus (55 mA)*(1.2 V) = 66 mW

To say that another way, the parallel arrangement did not seem to give 3 times as much current, for some reason.

I think these numbers are approximately correct, but the sunlight was varying a lot, due to the sky being cloudy. I tried to give you two occasions of "full sunlight" for both the series and parallel tests, but that was tricky because the sunlight kept kind of, uh, turning off, as shown in the 3rd picture.

Last picture is sort of a side view, so you can see my solar-workbench, which is actually an old refrigerator turned on its side. My back yard has a lot of junk in it, but I live out in the hills, so thankfully I don't have nearby neighbors who care if I'm making their neighborhood look trashy.

;-P

I was also shading my multimeter with a plastic bucket, just because I was kind of trying to keep my meter cool.

solar-cell-experiment-01-in-series.jpgsolar-cell-experiment-02-in-parallel.jpgsolar-cell-experiment-03-sun-behind-clouds.jpgsolar-cell-experiment-04-in-parallel-side-view.jpg
inconceivable1 (author)  Jack A Lopez5 months ago

awsome! yep those are the same solar lights. so im only 16 and dont have the privlege of ,like, anything. I dont have a job yet so funds are quite limmated and thus dont have a sotering iron and as you can tell i cant spell : P. but any way i sent you a pic of my solar arangemet just so you can see if everyting looks good. if its a go ill cement the whole thing in hot glue (basicly the most advanced tool i have) also a the only electronic parts i have (such as diodes) ive got from my arduino uno set so these are my last three diodes.

Screen Shot 2017-07-08 at 5.02.59 PM.png

Well, you know, tools are handy to have. Skills are handy too, but skills take time and effort to aquire them.

What's the old saying?

I started with nothing! And I still have most of it left.

;-)

Actually, these days, there are a lot of tools, particularly software tools, that are so cheap they're completely free, aside from the time involved in downloading, installing, and learning how to use them.

For example, my browser, Mozilla(r) Firefox, has a built in spell-checker, and it underlines in red, words I'm typing right now, that it thinks I have spelled incorrectly. So, for me, part of gaining skill in spelling, was just turning the spell-checker on, and also taking the time to try and learn from it from it; i.e. noticing the words it kept underlining, and trying to get those right next time.

Regarding the picture, it kind of looks like three of the same thing: a parallel group of three panels, in series with a diode, in series with a single AAA cell holder, and that looks believable, like it could actually put some current into the AAA, if the panels were placed in sunlight.

But you know, I can't "see" everything. I'm not clairvoyant. For example, from where I am, I can't see if the connections under the duct tape are closed or open.

But that is something you could discover for yourself, provided you can learn how to measure electric current. You know, like if the meter says exactly zero amperes, or milliamperes (mA), that often means there is an open circuit, something disconnected, somewhere.

Actually that happened to me yesterday, when I wired up the example with 3 panels, and 3 cells, all in series. The meter said zero, in full sun, and that didn't make any sense. It turned out, I just had to wiggle the wires on all those individual connections until I found the one that was open, but looked closed from far away.

Regarding your question about, "would it be alright if i followed you and messaged you when i have some electrical problems", that is fine. I almost always respond to PMs.

I'm not sure what good following me will do. Although there are other people doing this, for some reason. Maybe they're expecting me to write another 'ible, or something.

inconceivable1 (author)  Jack A Lopez5 months ago

alright well thanks for all your help. Turns out the solar pannal desing works cuz i left it out in the sun for about 3 howers and the batrys were charged enought to run the orignal lights all night. my big problem however is i used hotglue to hold the pannals togather and that didnt go so well. Think i have to use super glue instead. as for spelling thats pretty hopeless. thanks for helping me out i appreciate it! : )

Sure. Glad I could help!

inconceivable1 (author)  Jack A Lopez5 months ago

now right now i have my pannals in parrall but from your pictures it seems serize works better. however ive already had to rewire everything once and dont really look forward to doing it again so... i might just keep them in parrall we'll see. Anyway thanks alot would it be alright if i followed you and messaged you when i have some electrical problems im kinda a noob.

inconceivable1 (author)  Jack A Lopez5 months ago

sweet ill finish my configuration and lets compar notes see how things preforme. btw thanks for all your help : )

Downunder35m5 months ago

1. True.
By increasing the load until the voltage starts to drop you can also check the max Ma it can give you.
2. At the end, so read on...
3. Diodes between the panels protect them from overheating and damage if a single cell is partially shaded.
With no sum but power from the other cell it acts like a resistor.
4. You can measure the voltage drop on a resistor - that is how A meters work ;)

Now for the big number 2:
I played quite a bit with solar panels but started with proper modules.
Here all the normal stuff we learn about solar cells works out as expected.
Cheap cells from gadgets like garden lights that work with a maximum of 3V are a totally different breed.
As you noticed it makes no sense what get in output after putting them in series - the same goes for trying them in parallel.
In commercail panels for higher voltages we already have diodes between the single cell clusters and then another at the actual panel output.
These garden light ones have none at all.
Makes sense though if you check for what they are used...
Cheap, cheaper, sold...
All that is required for working is integrated into a single chip inside the light, it does the charging, light control and of course switches to battery during the night.
If you take just the panel and connect another to it than they will both have a different internal resistance.
Without any diodes seperating the single strips in your cells each one will count as a single resistor.
The more you add the more resistors in series you get.
On top of that comes the fact that these cells are designed to provide just enough power to charge the battery within 8 hours of full sunlight.
Which means really low power.
We could now calculate or measure the internal resistance of your cells but I think you got the point already.
If we now see all you single panels as a series of resistors and also consider all panles here then you see there is a problem.
The current goes through all of them so the single strip with the highest resistance will determine the max power from all cells.
That is why adding solar cells in series will almost always result in a slight ampere drop.
The bigger the cells the better to avoid this, one reason for the size of commercial panels.
Now take the sun and replace it with an external power source connected to a long row of resistors - your strips in the solar cells...
Each resistor will have a fraction of the supply voltage and with a load each resistor will heat up differently due to having a different resistance.
But since your cells are not really designed to provide much power at all the combined internal resistance will make getting a load to work with it next to impossible.
I dare all of our specialists here to grab a bunch of garden lights and find a proper explanation for the solar cell conundrum.
In my tests connecting more than 4 of these tiny cells in series always resulted in basically no output at all.
And before you ask: The cells had their polarity printed next to the connectors, so I can confirm it was done the right way ;)

inconceivable1 (author)  Downunder35m5 months ago

ok that is pretty awsome thank you for all your help. now i do have a few questions and comments

1. what does ma stand for?

2. so your saying the diodes do two things. keep the pannles from turing into resistors and keep the pannles protected

3. garden lights are a horable choice cus they put out harly any power at all and dont work well with other pannals

4. the reason why the end voltage in serize was so low was because the resistor factor each pannle possed basicaly equaled the volttage the pannle would have contributed.

Kiteman5 months ago

1. Yes

2. Solar cells have polarity - maybe you turned some around?

3. If your project has no batteries or other stored energy in it, possibly.

4. Make sure you are connecting the meter in series (not parallel like you do for volts), and see the picture I just snapped of one of our cheap school multimeters (I need to clean the lens...).

meter.jpg