This is a super simple project. No circuit board needed nothing, just scavenged components that you can just basically use whatever you can find. It's what I'd call an apocalypse project. Imagine the entire well, the majority of mankind obviously not you because you're still there.

Scavenging But imagine that, uh, mankind has largely been wiped out and there's no power, no fuel, nothing, and you're just Scavenging your fine solar panels and old products. You've got a diode, couple of old nickel metal hydride cells, random cells, and even some loose LEDs that could actually just be a scavenge. So I'm just digging one up here. A one watt LED in its own, or a bear still a string of lights because the strings of light are quite nice.

and uh, let's grab a notepad here and just doodle something up that we can do with this. So the solar panel would be something like probably about five or six volts. So say five six volts. Um, solar panel and the output of that would go through a diode.

Let me Zoom down this. Any diode, Just whatever you can find. It could be a 1n4140, a 1n400701. Anything you can find, even a Zener diode or rocker.

Though it's not really optimal for the application and we'd be using the solar panel to charge a couple of nickel metal hydrate cells. that I've chosen. a couple you could use three if you use a higher voltage solar panel, but I find that the idea of using two nickel Metro hydrate or a nickel cadmium if that's what you found and that would have its own uses. Uh, the if you had the three cells, it's got a slight disadvantages over the two cell, but would be suitable for a brighter use.

Now here's the point that this is the simple charger circuit. you've got. the any energy created by the solar panel in any level of light will go into charge these nickel metal hydride cells. I'd recommend a small one because otherwise if you used a really huge panel, it's going to bake these cells much like many of the solar lights do.

I'm just looking for the way buttons. so I'm not seeing a button cell that you'd find in many of sore lights that do actually get baked by Cheap solar lights. so you choose a smaller panel. I Guess this one's going to be about 50 100 milliamp and the number of sections of silicon one two, three, four five, six, seven, eight nine ten mean this is a five volt panel.

It's roughly half a volt per section. But any anything generated by the sun will go into these nickel metal hydride cells and it doesn't matter. There's no charge control because as soon as they reach their upper voltage of about 1.5 volts or the fuel capacity because it will usually float around that before they get there. uh, all that will happen is there'll be a sort of chemical reaction inside that recycles the liberated gas and electrodes and back into electrolyte and they'll warm up slightly, but they won't effectively overcharge.

It's not ideal to actually leave them hammered with a charge current all the time, but this is kind of designed just to harvest, uh, sunlight in the sense that it, for most of your own, they just barely top them up, maybe halfway or more. Then across that, you've got an option. You could have just a switch and a resistor if you wanted and an LED so that just whenever you needed light, you could turn the switch on and you'd have light. So say, for instance, you're in a cabin somewhere.

This little module is sitting there just happily charging the cells up. Whenever there's any light, you'd basically just add the circuit and it means you could have the option of a light on all the time when you needed it with a switch. the other option is to use a resistor just straight in line with the LEDs. That's what I'm going to do here with the this little string of LEDs and the idea is that it means it will be lit during the day, but whenever the sun shines, it's going to be partly making these LEDs light.

But it's also going to be topping these nickel metal hydride cells up to a degree OBS a balance you therefore you wouldn't can't really use too high a current. It's like basically it's a solar light, but it is just lit all the time. There's no dusk sensor. The other option you could put two resistors in series with your LEDs and this would allow a winter and summer mode.

The top resistor there would have a switch across it and say for instance, this one was 10 ohm for the summer mode. Whenever the switch was closed, the current would go straight through that low value resistor and it'd make the LED light quite brightly. You could have say for instance, a 47 Ohm resistor here and it means that in Winter When there's less sunshine and you open that switch. It would add the 47 ohm in series of the 10.

it just means that the entire should be lower, but it would make the most of whatever Sunshine was available. Let's build this noting that the negative connection is common to everything, which makes it easy. You could put the diode anywhere. really.

Um, you could put it in the negative or the positive. It doesn't really matter in this application. So here's a solar panel and here is the connector I'm going to use to connect to my lights and here's the battery pack. Let's get the soldering and just Cobble this together.

So I'm going to twist the two negatives together and put some solder on them and I'm going to tack them onto the negative connection solar panel. This is the sort of thing that if you wanted to make decorative lights are just powered all the time. I mean this would be really nice and you know off grid cabin. you could have a set of lights that basically a smaller ornamental tree with LEDs in it that would just stay lit all the time.

It would be nice during the day with a solar power lighting and then when it ran off the batteries at night it would just be quite a nice Ambience it would give and also give that comforting glow in the place but not too bright because it it'd be nighttime you'd be trying to sleep although it helps to have a little bit of later times. So the diode. any diode. in this case.

I'm using a one in four double O7 because it's what I have lots of because it's a high voltage diode. it just does everything. I'm soldering that with the band pointing away from the positive connection. Now I'm going to cut the other end short.

I'm going to put some solder on it. This is such an easy project and I'm going to twist the two positives together in this instance, noting that in this lead that I'm going to connect. LEDs I've already got a 10 Ohm resistor. The choice of resistor will depend on the size of the solar panel and how much sunshine you get locally.

People in very dark climates may want to use a much higher value of resistor to limit the current more, but having said that, that's the advantage of using the Tunica metal hydride cells is that as they discharge, the voltage drops the point. the LEDs will just glow gently and even if one of the cells well, one of the cells won't go really flat because as soon as it's below about 2.4 volts the combined voltage, the LEDs will stop conducting which is is quite useful. It just means it protects the cells from reverse charging. As could happen with three cell version, the three cell version does an advantage of offering much greater brightness.

That's it. The project is complete. Let's stick the batteries in. let's plug in my little string of lights.

I like like the idea of surviving an apocalypse I Think most technical people would be in a good place to do so and I put the cover on, the LEDs are lit and uh, if I was to hold this up to the bench light, it's actually you probably won't see the LEDs will get a little bit brighter but uh, that is it actually putting more current out than the LEDs are using. So at this point in time it would be charging. and yet at night time when all the light went off I'll just take the splitter off for this. You'd have your little decorative lights that just run 24 7 and as I say indoors.

and if you had to say for instance, you had a little decorative tree or a an ornament with LEDs on it in a sort of Darker corner of the room, these would be lit all day long. um, and well, 24 7 um powered by the sunshine or daylight during the day. Whatever you could get and power the batteries at night and the solar panel, you might get off with just putting it in the window. Um, but other than that, uh, you could.

Theoretically, if you wanted more sunshine, you could Mount this elsewhere you could mount it remotely. it doesn't even have to be close to the system. you could have the battery indoors with next to LEDs and just two wires coming down from this and have the diode mounted locally or at the solar panel itself and just put it in a waterproof enclosure in the distance. wherever you put it on the roof, up in a tree, on a post, anywhere you wanted it.

it's a simple project. It's a very nice project and to be honest, I could see that being very useful in that sort of end of world scenario.