Hi, I've got a bit of a problem. I've got one of these 18650 rechargeable lithium ion batteries. You're no doubt familiar with these. they're used inside torches and laptops and all sorts of products these days, But actually, I got this out of a torch I've got, and that's the only product I've got which uses an 18650.

believe it or not. So I don't actually have a purpose-designed charger for this thing and it's just gone flat. So what am I supposed to do? No worries, we've got a lab power supply beauty. Let's see if we can charge it now.

Charging these 18650 cells or any lithium ion or lithium polymer cells can actually be quite dangerous if you don't do it correctly. So click here If you haven't seen my video, it's an old one on a complete tutorial on how to charge lithium-ion batteries. So this will just be a quick video on how to use a lab power supply to actually charge these things relatively safely. And by the way, what I'm going to show you here not only works for 18 650 cells, it works exactly the same for lithium polymer Lipo cells as well, which you get in all sorts of remote control stuff and things like that.

They're basically identical from a charging point of view. Now, this particular one from Lumentop actually has a built-in protection circuit and it's in the end cap here, and sometimes they're actually slightly longer in length than your regular ones that don't have the protection circuit in them, and this will actually mostly protect the thing, but we're not going to rely on that today. We're going to assume that we're using a charging an 18650 cell that doesn't have any protection built in, so we have to know what exactly what we're doing now. Lumentop Don't actually have a data sheet for this thing, but it does tell us that it's a Panasonic Ncr18650b cell.

It does say it uses Panasonic cells in particular, so bingo, We can actually get the data sheet for this Panasonic cell. So the specs rated capacity: 3200 milliamp hours. They put 3 400 milliamp hours. Yeah, I don't know.

We might not have the exact dart sheet they might have like an upgraded cell or it could just be marketing wake. Who knows. Anyway, Um, it is going to have all the data we need for the charging and we've got a charging graph as well. Beauty.

Now it must be said that not all 18650 cells are identical in terms of charging. Same, some can be, uh, they're designed to be charged at a higher rate, others might have a slightly different voltage depending on the chemistry in there. And I won't go into any of the details because as I said, I've done a like a 40 minute video explaining all the ins and outs of Lithium-ion charging. so go watch that.

But we'll do a quick overview. So there's two things you need to know to charge a lithium-ion battery like this. You need to know its nominal charging voltage, which is critical. This one is 4.2 volts.

As I said, it can change depending on slight chemistry differences and other manufacturing differences, but 4.2 is pretty much the majority out there are going to be 4.2 and it must be 4.2 Like, plus minus one percent. It is quite critical. Uh, so all the Lithium-ion charger chips out there might be say half a percent accurate or uh, something like that. So we need to be fairly accurate on the voltage we're going to use to actually charge this thing.

And just any regular three and a half inch digital multimeter should be at least 0.5 percent accurate, so it's going to be good enough for the purpose. In addition to the voltage, we also need to know the charging rate. Nominal charging rate. In this case, the charging standard rate is 16 to 1625 milliamps or what's called 0.5 C because the capacity is 30 200 milliamp hours.

So we need to charge this at half of its nominal rated capacity or nominal rated current. You just take away the hours there. 3.4 3, 400 milliamps is 3.4 amps. We need to charge it at half that or 1.7 amps.

And charging lithium ion batteries is a two-step process. As I said, I have a video explained in much more detail than this. There can be like a pre-charge section and all sorts of stuff. Anyway, this is a very simplistic thing.

There's a constant current charge mode where first of all, it charges at a constant current for a period of time and then it goes into a constant voltage mode. And this why this is why these need intelligent charging Ics to charge these lithium ion batteries. But our lab power supply, by the its very nature of having a constant current in constant voltage modes, is going to be able to intelligently do this for us. except it won't have an automatic cut out at the end.

So what we've got here: Voltage on the Y, Y-axis Time on the X-axis here. Now this blue curve here is the cell voltage and let's say the battery is dead and it's like at 3.25 volts or whatever. Okay, it's it's a dead battery and then we want to charge it up so we have to charge it in constant current mode. This other y-axis here is current so you can see this is the green is the current used to charge the cell, so you can see it's a constant current in this case 0.5 C.

as we said before, or 1.7 amps. So we need to drive a constant current through this battery for a set period of time at 1.7 amps. and then if we do that, the voltage will naturally rise. Like this rise rise rise until it hits that 4.2 volts.

that magic 4.2 volts cut out voltage, which as I said, is quite critical. Otherwise, you can damage the cell. It can explode and heat up, do all sorts of horrible things you don't want to know about. So you need to detect when it's at 4.2 volts and then switch into constant voltage mode like this where then when we're putting a constant voltage on it, the current will naturally drop down like this, and then the cutoff point is usually typically around like 10 of the charge current, for example.

So you know 170 milliamps for example might be a cut off thing. It doesn't show you that here, but anyway, there's different schemes for that, but that's the basic two-step charging process. And the great thing about using a lab power supply like this is that they have constant voltage and constant current modes so we can set our voltage our maximum output voltage of for you guessed it, four point, two, zero, zero volts and this is quite an accurate power supply. This, uh, Rygold Dp835.

It's like 0.05 percent accurate. So yeah, we can be pretty confident that 4.2 is going to be 4.2 for our purposes. more than good enough, order magnitude better than what we want. And then we need to set up our constant current mode or our maximum current that can be drawn of 1.7 amps or 0.5 c for this particular cell.

And the good thing about a lab power supply like this is it will automatically switch it. It will never ever deliver more than 1.7 amps. and it will never ever deliver more than 4.2 volts. So if we go back to our graph here and have a look at it, this is exactly what we need it to do in this mode here.

because we've got it set to 4.2 volts maximum in constant current. It'll draw that constant current. It'll try and draw more when you initially switch it on. it'll try and draw more current, but it'll be limited by that 1.7 amps that were set.

so we'll get that constant current mode. and then when it actually reaches 4.2 volts, the power supply won't let the voltage that blue line go any higher than that, so it will naturally limit that. And bingo, we will be in constant voltage mode. And if you actually had a lot of power, supplies will have a constant current mode Led on here.

They'll show you when they're in constant voltage or constant current mode. So lab power supplies are perfect for this sort of application. But as I said, the only thing it's not going to do is automatically cut out at the end. It could if you had some fancy pantsy programmable supply.

which this one is. but I'm not going to use that because most people will not have a programmable supply. But look, the charging is specified at a maximum of four hours, so we can just set a stopwatch for a countdown timer for four hours and get it to go ping when it's finished. So I do happen to have a an 18650 uh battery holder lying around so we can hook that up across here because as I said, the voltage across here is critical.

but if you set your 4.2 volt limit on here, worst thing that's going to happen is you're going to get a voltage drop and you're going to get a lower voltage on here. Which isn't necessarily a problem, but it's but it can't go over 4.2 so you are actually protected. Your cell's not not going to explode on you. Ok, and we've got our 4.2 volts maximum voltage set up there and our 1.7 amps.

So let's go and switch this thing on and it will enter that first phase that first constant current phase of this. so we should see it go to 1.7 amps and limit. So let's switch it on, make sure you've got the battery around the right way and let's switch it on. Bingo! 1.697 amps and the other thing we want to do is to protect it.

We want to set our timer, so let's go in there. I set my timer to four hours. Let's start that it'll count down. This will beep at me at the end of four hours because you don't want to leave this running overnight or something like that.

You can overcharge the cell, damage it. You don't want to do that even though it's sort of a bit self-limiting Just yeah, you want to cut it off after about that nominal four hours and you want to use your battery, don't you? But what you can see is that the voltage on the cell is slowly rising with that constant 1.7 amp charge on there. So that's exactly what it's doing. It's charging at a fixed 1.7 amps because we set that and the voltage is slowly slowly going to rise and you'll find that after maybe I don't know.

Time says 100 minutes here. Whatever it is. Um, it'll change depending on the cell and all sorts of stuff and and the initial uh, discharge voltage and how much capacity was in there, etc. So it'll charge up until once it hits 4.2 volts, the power supply will automatically switch out a constant current mode and we'll have 4.2 volts on here.

and then we'll see the current start to drop. So I'll leave that running and get back to you. And after two hours, we're still charging at 230 milliamps. So there you go.

we'll wait. I'll wait until it gets down to I don't know, maybe five percent of the 1.7 amps or thereabouts. Sorry about the focus on this. I goofed it up, but you'll be able to see it.

Uh, that little Cc mark for constant current mode and you'll be able to watch it switch to a constant voltage mode just there. Once it hits 4.2 volts and just over three and a quarter hours. Oops. I stepped out and I let it go.

Um, well, further than I wanted. But it it doesn't matter. It's down to 26 milliamps now and that's only like 1.5 of our original charge current and that's probably as low as you need to go. It's diminishing returns from this point.

most of the energy is being put back into this thing, so leaving it longer is not going to help. As I said, anything under that 10 mark 5 maybe would be a typical cutoff figure of that 1.7 amps that we were charging at there. So yeah, we'll call it quits. And you don't want to, actually, uh, trickle charge or float charge lithium-ion batteries like this because it can, actually, uh, build up or plate the uh, lithium inside the metallic lithium inside the battery.

And yeah, you don't want to do that. They're not designed for that. There are, um, there are chipsets designed for float charging and they use like a pulse. Uh, a slow pulse type system which I've mentioned in the previous video.

I think so. Yeah, you definitely don't want to leave this over running overnight overnight. probably won't You know it's not going to leak and damage your battery too much, but you don't want to. You know, leave it too much further.

Anyway, you want to use your battery, so take it off once it drops below five or ten percent. Yes, you can, actually, uh, take it off at any point during this charging process and use it. You can take it off when it switches from constant current to constant voltage charge mode for example, and you might, but it's only going to have like half the capacity uh, put back into its or something of that order so you know it depends on how much charge you want to put in. But as I said, once you get below that five and ten percent, five percent.

Uh, figure here of your uh, half C charging or your charging rate, then it is very much diminishing returns. So at the end of that, we can just switch that off And Bingo! we've got a fully charged battery, you little Ripper. And yes, you'll see the voltage are slowly dropped down and it'll stabilize at a particular value. So there you go.

I hope you enjoyed that video of how to charge a Lithium ion rechargeable battery, not Lithium primaries. Definitely don't do this on Lithium primary batteries like coin cells and other type batteries. Lithium Ion rechargeable batteries with your bench power supply little Ripper If you liked it, please give it a big thumbs up. Catch you next time.

Hi, it's lithium ion battery tutorial time. There are actually two different types. Don't confuse these with lithium ion or lithium polymer because they're the same thing. In fact, they're the uh, new type of anode material.

It won't go into the construction of batteries, you can look those up yourself, but the anode in there can use two different types of materials. This is, uh, very simplistically, what's inside a lithium-ion charger.