A solar powered shed light? Let's open up and see what's inside. The picture in the front shows quite a lot of sections of silicon in the solar panel, but that is not always a guarantee you're going to get much silicon on it. This one came from a local shop which makes our refreshing change. it did not come from eBay came from Jacks and Ramsay in the Isle of Man.

So there's the light and here is the solar panel and a bracket. What's the racket? Go under other bracket Clips in here. Okay, I'll put the box out the way. So first thing I'm noticing here is lots of silicon.

This is good. It's actually pretty much filled this area. so we've got one, two, three, four, five, six, seven, eight, nine, ten eleven. So it's a 5.5 volt panel.

I Think it said in the box so that's all squished up I Think I said in the box that it was three points and volts suggesting it's the the classic 4.2 volt lithium cell because that's a mid voltage. Let's plug it in, plug it in and it lights, so that's not bad. Um, right. let's take it apart.

I'm guessing that the battery is in here I Don't think it's in 18650 although they could fit one in here. Let's open it four screws. I'll open the light as well and we'll see if there's much in it. I Would expect to let him sell to be in this one because it does have a switch on it and it does seem to have that Vibe For structure there is, The Lithium cell battery must be recycled or disposed of properly.

Oh you don't just throw in the bin. Date code: 15 for 2022 which is pretty good so you can get it out. Can I get it out? Maybe not Fingernails Smart store. Listen: 500 milliamp hour.

It's a 14 500 which is a the size 14 millimeters diameter by 50 millimeters long and three point symbol. So is this a 4.2 volt cell? Let's actually hike that out since they're going to be getting the circuit board out anyway. I Want to see also March in the back 14 500 3.7 Let's Zoom down this. What I'm seeing here initially is not much.

Is there anything else In the back of that circuit board? there's the chip Aster and a resistor. Is there anything in the back? so take these two screws out. Just the switch. That is it.

There's a chip for number on it. Eight, one, eight, three. Okay right. I'll take a look at that circuit board.

let's pop this open and see what's inside this. So is this just going to be there? Well, this is just going to be the LEDs but are there going to be resistors as well? Let's Zoom back out to here. Is it going to be something sophisticated or just a panel of LEDs? Maybe just one or two. LEDs Last few turns in that screw, we have a huge sneaking parallel array of LEDs There's a little pull cord, switch, power jack.

That is it. All the circuitry is in that unit there I Wonder if that resistor is the series resistor for these then right? Okay, tell you what. I Shall uh, take the circuit board out, take a picture of it, and uh, we can reverse engineer it and see how this works one moment. please and resume.

It's the first time I've seen this particular chip. This is a Yx8183 and it's like the classic little four pin boost chips you get in standard solar lights, but this one is optimized for Lithium use and it lets you choose whether it's going to be a standard lithium-ion battery or a lithium ion phosphate. So the only two components on it are a decoupling capacitor across the battery because this also controls the charging that's to provide stable detection of the battery's charge condition and also 0.33 Ohm resistor which isn't in seriously? LED Well, it isn't Sears the LEDs but it's being. It's got a 98 millivolt threshold on here that's .09 volts and it detects the voltage drop across that and it's got a built-in current regulator for the LEDs Very interesting.

The reason these Uh pins are all connected to the negative here is because they are programming different functions. So we've got the switch here. This is a switch that, uh, ultimately, You may wish to just shut this out. Once you get it, the only time it's ever going to really be used Is in long-term storage.

But I'd recommend just chanting these out because when water gets in, they do feel. and we've basically got a connection for the solar panel and a connection for the battery and then the output to LEDs. That is it. Right now, let's take a look at decision decisions.

Let's take a look at the chip itself. first. cue the data sheet. I'm going to team this down a bit teaming down now.

So the chip has two distinct sections. It's got the battery charging current regulation section and then it's got the LED driver section. The solar panel connects here and it goes via this fat to the battery and the battery voltage is sensed and you've got our mode pin down here. Now if that mode is tied to negative, it sets it for the standard 3.7 volt average voltage battery the one that charges up to 4.2 volts.

But if you either leave it floating or you take it to the positive rear of the battery, it will effectively turn it into a life Po4 unit and it will adjust all the voltage thresholds accordingly. not just the end of charge voltage level, but also the point it cuts off and and stops driving. the LEDs and then the pointer will actually cut back in again because it does have hysteresis. It does that of that little voltage threshold that once LED is cut off, they won't just cut on on again until the solar panels put some charge back in.

Other things worth noting: there is the feedback sense resistor and it's got a sense voltage of 90 millivolts on that PIN Um, which means that as the current flows through, that mosfet will just vary its output to regulator. and in the case of this one, it was a 0.33 Ohms equates to 273 milliamps. It's roughly measuring 90 millivolts at that point. It's got an enable input Not sure why, but that was just tied low.

and at CDs now I'm guessing that's cadmium sulfide. It looks as though that's for the option of either adding a light sensor or sensing the intensity level from the solar panel itself. but in this case it is tied to the negative connection. Which means it's just on all the time because this is a shed light.

I Tried the light in a dark room in the house and it was surprising how much light it puts out. It was very useful. Here's the schematic and no need to draw it, just add some color because this is the manufacturer's schematic. the solar panel incidentally, and I don't like this aspect of it I Like the solar panels where they've got the silicone strips bonded onto fiberglass and then the layer of resin over the top, but this one, it looks as though it's just they're laid onto the plastic and then they've got the resin on.

And the downside of that is I've found the pass that some of these solar panels have a different thermal coefficient of expansion of the silicon and the plastic and resin and it can actually in hot. Sunshine It can actually crack the solar strips I'm not sure if that's going to affect this one or not, but if it does, you usually see a distinct white line appears across them and when it does, that really impairs the whole solar panel. It hobbles the whole thing. Quite annoying when that happens.

I Don't know if they still do it. Let's Zoom down this a little bit since this is what we're wanting to see. So in this case, the current Cent the light level sense instead of being tied to the top of the solar panel via a resistor. Don't know if that resistor turns the level it chips out or if it's just to basically avoid current just going straight.

I'm not really sure why if that resistor is essential or not, but that's not used. It is literally just tied to negative. The blue here indicates all these pins are tied to negative. The LX is the switched output LEDs red is the battery positive, orange is the solar panel positive, and the feedback is the sound resistor for the LED current.

There's a switch to show on the schematic for choosing between the 3.2 volt Lithium cell and the three-point symbol lithium cell that can apparently just be left floating, but in this case it is just tied to negative. The solar panel the only capacitor is the one directly across the battery here. Um, and about the LEDs connected between the positive output the battery through that mosfet inside, through that current sense resistor to the zero volt rail. that is it.

There's not really an awful lot is there. It's a very good, very simple, so that is more or less. It set a nice enough little light. It does put out a useful amount of light under air that current it's going to give you.

Given that it's current regulated, it's not going to do that thing that then tends to gradually lowers it. It's pretty much going to run at the full intensity all the time. and you can change that resistor if you want. If you've changed it from one extreme to other 0.23 If you increase the value, the current goes down.

For instance, 10 Ohms is 9 milliamps and the other thing is it relies purely on the amount of current the solar panel can put out. You cannot exceed 600 milliamp, but in this case I Think this one is about 150 to 200 milliamps Max for these size of air solar strips. But uh, it's basically just a taking all the energy, all the current that comes from the sword panel and putting it straight to the lithium cell to top it up and then turning it off. It doesn't have that current regulation facility, it is purely basically whatever there is it puts to the lithium cell and that is it.

It probably still is that slight issue that these things have. Technically speaking, you shouldn't charge a Lithium cell below zero degrees Celsius which is not great in a sunny Winter's day, because what happens is that the the lithium cell operates by the lithium ions moving back and forth between the two electrode materials and the lithium ions do what's called intercalcation. They actually blend into the material as they go across at very low temperatures. I Don't know if it's like molecular contraction material that the lithium can't get in, it forms a layer on it instead, and that can increase the damage the battery in the sense that it's a concentration lithium in one area, but it can also potentially damage the thin divider membrane if it doesn't form up in a sort of controlled manner.

It can actually pierce the membrane. But that's just one of these things. I Think it's just Collateral Damage I guess I wouldn't you wouldn't really? Maybe put this in a flammable surface? I'm guessing I've never I've seen the batteries exploding, blow the guts out, but not burst into flames as such. and I don't know how that will affect this one, but ultimately, if it's going to charge at Sub-Zero temperatures, yeah, it's going to affect it.

Um, I Suppose Ultimately, if you were in a situation that was an issue, you could have a separate enclosure for the Lithium cell and put it inside in a sort of protected area and not really sure it depend on the application, but that is it. the fairly neat little solar shed light. It's actually not too bad at all, and that chip is really interesting.