A really popular lithium battery charging module on ebay is this one hold on i'm just going to zoom in on this because uh, it's tiny, and this takes a usb supply in and then regulates the current and controls the charge, depending on the voltage across the lithium Cell and i thought i'd take a look at a newer version of this that does higher current by basically just having a stack of four of the current uh regulation chips in parallel. So it basically multiplies a current by four so to understand how these work, let's zoom out, actually willing to zoom out hold on. I shall bring in the straw. Yes, i'll have to zoom out it's enormous, so this is a little tiny circuit board.

It's so tiny that didn't really zoom in that well, but we've got the five volt supply coming in, which can either be in these outer pins or the usb connector and they've left their options open for a couple different types connectors here, but that goes via a 0.4 ohm resistor, which to be fair, is shown in the data sheet but isn't always used by people. Then there's a decoupling capacitor for just filtering any sort of noise across the incoming supply for stability, the current regulation chip and then an output capacitor to the lithium cell that goes across here. There are two leds, each with its own resistor, and the other circuit only uses one resistor as i'll show you in a moment, but one of these indicates that it's charging and the one indicates that the charge is complete. Then the only other remaining thing is this resistor down here, which programs the chip, depending on its value, how much current it's going to put out to the lithium cell.

In this case, it's a 1.2 k, resistor one two and two zeros, and that programs it to one amp and it's worth mentioning that if this is putting in five volts and the lithium cell is quite low at three volts, it's dropping two volts across this chip. It acts as a new linear current regulator, so it'll be dropping two volts at about one amp it these chips get hot under that load. It's worth mentioning that it's actually better to program it to lower current, and that also protects the cells. But let's take a look at the other circuit, so i'll take this one out of the way i'm just going to use the full width.

Oh that's, not bad! I shall zoom in. I shall zoom in till it fills the frame. So what we have here, we have the incoming supply connect. You've also you've got the option of these two connections here or you've got a little jack connector and i have to say this was perplexing because it has two pins and it took me a moment to work out that one of the pins it should have three And one was completely missing.

I just thought it was a different style and i was trying to work out which way it went round. If you do get one of these kits make sure you meter out. What's the positive, it's usually the back one and which one of these is the negative when it's actually plugged in because these pins act like a switch and it disconnects it's for disconnecting internal batteries when you've got an external supply. It's a standard feature of these jacks but make sure you meter, which one and color it, and so that, because you can put the connector in various ways around and just make sure you're putting it in the right way around, because if you put it in the Wrong way round - and it is possible to do that with some connectors you'll - get the polarity the wrong way around.

Not it really matters, because there are two protection darts, it just won't work. So there are two protection diodes. Then there is this stack of four chips and plenty of the decoupling capacitors. Each chip has its own current programming, resistor and then there's only one other resistor and that's a common resistor for the leds.

You get this little three lead led with it. Uh, red and green chip with a central common that provides positive to the central common. Then it pulls to negative uh. On these, i get the urge to actually try that, let's just uh full run, these leads up, make that one positive and see if it's actually going to work.

Yeah, that's quite bright red, hmm, okay, in this case, they are just using one resistor for both those uh. Both those leds right tell you what let's take a look at the socket diagram of this. When we look at the circuit diagram, we've got the five volt in we've got the two schottky diodes just for polarity protection that also drops roughly about 0.2 or so volts, which takes a lot of strain off these chips. But it does mean the diodes themselves will get quite warm at full current, particularly given this thing is charging at pretty much three amps we've got the 1.2 k.

Resistor we've got the two leds going to the tc4056 and you may notice i've written tp4056 because that's what this is kind of cloned off thing and the search keywords to find these modules are tp4056 3amp. The chip itself has the positive in it's got the enable tied high to enable the chip. It's got the negative and it's got the temperature monitoring chip, which is the facility for a thermistor on the batteries. It's got that tied to the negative rail because it's not used.

It's got the programming resistor of 1.6 k that equates roughly to about 700 milliamps, i think 700 milliamps and because there are 4 in parallel. That means that if each one is passing 0.7 amps 0.7 amps times the four chips doing it all together equals 2.8 amps. There's your roughly your three amp charge current! You do have the option of changing those. Those resistors yourself.

If you wish, if you want more control, but having said that, if you go too low, you might as well just use one of these particular ones with protection, and there i've just drawn there's one in the input. There are two of these coupling capacitors one at each end of the circuit board. There's one there and there's one there, but for each chip it has its own little local, decoupling, capacitor for stability or bypass capacitors. Some people like to say it has many names, but only one of the chips is used for to drive the leds, the other ones all just have their charged status, pins floating because they're simply not needed, and these chips are so cheap.

I mean you're talking for this whole circuit board, you're talking about three or four pounds, uh, say five dollars or something like that. It's just they're very cheap. It's just the easiest way to achieve this, but the circuitry. Basically, if you just blank out this resistor and the two leds, it just multiplies that by four and puts them all in parallel to provide the higher current to the lithium cell and it's nice that they're not pushing these right up to the one amp they're.

Only running them at 700 milliamps, which is lower dissipation across these particularly helped by these diodes in series. So that is it. If you get one of these just uh, i would say the only thing to note is be careful about it, making sure that you check the polarity of this little connector because uh, if you get the wrong way around it, just it won't work or potentially in Some instances you might be able to short then coming the supply out, not sure i'll, have to get another one of these connectors for this or i'll just jump our wires on. Oh, it's worth mentioning it's a double-sided board, but the back of it is basically one common negative plane, except for one that will track which i've drawn here.

It's the one that connects the resistor to the middle of the leds. The rest of it is just a solid plane connecting from these negative connection pads to this output, negative pad and then under each of the chips is a couple of plated through holes, uh just to couple the negative locally to each of the chips. That is it. It's quite neat: it's not a bad concept, copied left right and center.

It's like someone's, obviously come out this idea and it's been copied and mass, but um. It's a neat solution to providing that higher charge. Current in a very simple package.