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I recently discovered there's a "thing" going around where people are charging lithium cells by attaching a stripped USB lead directly to them.
Normally lithium cells are very safe if undamaged and correct charging procedures are used. But overcharging them like this can result in cell damage and potentially fire.
Many of the "found" lithium cells salvaged from disposable devices have no extra protection circuitry because it's not needed in their application. But when recharging them it is very important to control the charge current and stop charging at around 4.2V
Direct charging with a USB lead has very little current limiting and the charger will often smash more than its rated current into them, potentially damaging the charger too. It will also keep charging them beyond 4.2V and that poses a genuine risk of internal chemistry damage, potentially resulting in avalanche failure where an internal short circuit occurs. If that happens the full energy capacity of the cell will be released extremely quickly resulting in the electrolyte venting as a flammable vapour, and if sparks blow out too it can ignite resulting in a flamethrower effect.
I want to stress that lithium cells are not dangerous because of the lithium. There's very little lithium metal in a rechargeable cell, and it's diffused through the electrode materials. The real hazard is their ability to store and release very high amounts of energy. (Like an overloaded Star Trek phaser.) If used correctly and protected from physical damage, lithium cells are very safe.
You can easily and cheaply get TP4056 modules on eBay that let you charge a cell correctly from a standard USB lead. The keywords to find them are 5pcs USB TP4056. It's often cheaper to buy them in packs of 5 or 10. There are two types - with or without the extra DW01 protection chips. It doesn't add much to the cost, which is less than 1 £$€ per module.
If you are OK with soldering surface mount resistors you can swap the existing 1.2K (122) resistor for a 2.2K (222) one to change the charging current from the standard 1A to 500mA. Alternatively a conventional quarter watt 2.2K resistor can have its leads shaped for soldering to the surface mount pads. The ideal charging current for a lithium cell is equal to its capacity in mAh. So a 500mAh cell is best charged at 500mA, although 1A can be used for faster charging at the expense of capacity and charge cycles.
So far all the cells from modern "disposable" vapour devices that I've tested have taken a good charge. When salvaging cells for use in projects use common sense and caution with recharging. At this point in time the cells do seem to be standard rechargeable types, but that could change in the future if they discover a cheaper option.
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This video is about how to charge a found, lithium cell properly and, more importantly, how not to charge a found lithium cell. In a recent video, i've featured vapor devices that can be found lying in the gutter on the street that actually contain a rechargeable cell of decent capacity. I've tested one of these cells. It was spectacularly good performance and after i published that video people said, oh yeah charge that myself, by getting a usb lead stripping the ends and putting it straight across the lithium cell and plug it into a usb charger.

Do not do this. There are so many reasons not to do this and i'm going to demonstrate them right now by showing you what happens and what could potentially happen. If you do that, so here is a fairly beefy, lithium, uh, well usb charger and i'm going to plug a analyzer into this. This is a little rear, deng analyzer and keep in mind.

You only really want to charge these cells at about 500 milliamps to one amp. If you plug it into a usb power supply straight as it is, two things will happen, it's gone to over three amps immediately, which is way too much current for that cell and, more importantly, the usb charger is going to try and charge this cell up to 5 volts - and you must not do that - it will not only potentially damage the cell and reduce the number of charge cycles you get out of it dramatically. But if you over charge these cells above about 4.2 volts, which is their normal, safe charging level, it can cause chemistry problems inside not just depleting the lifespan of the cell, but it can actually make them fail and when they fail, they can sometimes go short circuit. Inside you'll get a jet of vapor coming out the end, if that vapor, which is combustible, light you'll, end up the little flamethrower, and if you've got this charger in your house um and you forget about it - you might come back to a house.

Fire just thought. I'd mention that now i don't want to be alarmist here um. I don't want to make it out that lithium cells are a terrible thing, they're a great thing, they're one of the best battery technologies, but you have to treat them with respect. You have to make sure you don't physically damage them and you have to make sure you don't damage the chemistry inside by over charging them.

So i'm going to show you some ways to charge these and uh. They will be based on these little modules. You can buy from ebay, they're very cheap, you don't just buy one of them buy a strip of them because it's actually cheaper to buy them in bulk. If you go on ebay and search for tp4056 module i'll provide a link down below to a search for that, then you will find sets of these available for sale.

There are simple ones and there are complex ones. Now there is another scenario with this: some batteries that you might find that are salvaged from equipment do actually have a protection circuit built in in that case, if you were to just slam current into these with a usb lead, it will still over charge it current Wise, but it should actually cut off at the 4.2 volts, but it's not an ideal thing to do. The only thing that is limiting the current is usually the cable itself and it's not an ideal situation. It's very unpredictable.

Let me show you uh the circuit board. That's in the end of this cell, it uses two chips: it's got the dw01, which is a special chip dedicated to protecting lithium cells, and it uses a little double mosfet. The reason for the double mosfet is so it can actually stop that charging when it reaches the upper level and also, if you over discharge it it'll, also cut it off to stop the battery being just run right into the ground. There are very few support components needed with these i'm going to cover these, because the same components are actually on one of these circuit boards.

So, let's take a look at that chip in the first place, the dw01a. This little chip has the mosfets and if you connect the cell across it, it monitors the voltage across the cell with a 100 ohm resistor and a 100 nano farad capacitor. This just provides basically a bit of decoupling for any sort of noise from the load that's connected, and it means that it can actually accurately monitor the voltage across that cell. It also does one other thing: um.

It has a 1k resistor here and it measures the voltage across these mosfets and if it exceeds 0.15 volts, it will actually turn the mosfets off to protect itself. So that's the short circuit protection that does not work when you're charging it. As far as i know, only when you're discharging, but this thing is a sort of it's useful - it will actually cut off at 4.3 volts, which is above the normal 4.2 volts and it'll cut off at 2.5. Volts from your discharging.

It is basically purely to prevent extremes from uh going too far. So let's take a look at the first of these modules you can buy off ebay, then i'll, show you how to hook some leads up to them. So you can reuse your cells, lots of times. I've got a little one here, a little module that i've doctored up, that i've been testing.

This is out one of these type of device, and this one this cell is rated about 500 milliamp hour. This particular one. I've run several full charging discharge cycles at sensible currents, 500 milliamps and the first one. Well, i missed the first few cycles because it's only after i'd done it a few times.

I thought i should be documenting this and consistently it's gone after the first few cycles. It went up to about 481 milliamp hour and over one two: three: four: five: six: seven, eight nine 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, plus all the previous ones. So, let's say 25, it's at 485 milliamp hour, which is very respectable for a 500 milliamp hour cell. That is well within the tolerance, and it shows that you know these salvage cells have a lot of uses.

So here is the first of these little modules. You can buy off ebay, it's a fine module. It doesn't have that extra layer of protection. I prefer the other module that has it, but let's take a look at it, so we have the classic chip.

This is a charge, control chip and it has a resistor here that sets the current most of these comes set for the maximum current, which is one amp, and while that's not ideal for these, if you're not really comfortable with changing this resistor, this tiny little surface Mount resistor, which uh you can also just replace it just by soldering to adjacent pads that are bigger. You can just replace the quarter watt resistor if you want, but ideally for compactness you'd, replace it with another surface mount resistor at the moment. It's one point two thousand ohms uh, but if you change that to two point two thousand ohms, it suits these batteries back to these little lithium cells, because it will charge them at 500 milliamps and you can customize that it's a nice it means it'll, take longer To charge than just the bare unit as received from ebay, but it will just treat the cells a little bit better and they'll last a bit longer. I should put this device down, i'm not going to puff that, but this chip has other tricks.

It shows you when it's charging, it shows you when it's completed charging and it has various things. If the cell voltage is too low, it will start trickle charging at one tenth of the programmed current just to get it started gently. It also has thermal regulation. If it gets too hot, it will actually cut back the current itself, so the circuitry on this particular unit looks like this.

The usb supply comes in and it goes to the chip via a 0.4 ohm resistor, which is kind of it's shown in the data sheet. But many don't use that i think they're, relying on the resistance of the usb leads, but there's a 0.4 ohm resistor and a little local decoupling capacitor to provide stability for the chip. The current is programmed with this resistor here and if you look at the data sheet for the chip, let me just grab the data sheet for the chip, because it's got a set of resistance values here, so it goes from the default value that supplied these modules. One point two thousand ohms will give one thousand milliamps or one amp output.

I experimented. I found 2.2 000 ohms gave around about the 500 milliamps, which is just in between the 4 and 580 here. But if you've got really small cells you can put in up to 10k as a resistor. You can actually go much higher than that, but they don't really document it, but that will charge a very low 130 milliamps, which is ideal for really tiny cells.

It's a very versatile chip. It's super useful things worthy of note. The chip terminates charge at the end when it detects that the current you've programmed say, for instance, this is the as supplied from ebay. It's set for the one amp, because it's got a one point: two thousand ohm resistor.

It's only when it the current tails off to 100 milliamps that the fully charged indicator will light um. It's worth mentioning that if you have a 500 milliamp hour cell and you're charging at 500 milliamps, then after an hour, even though it takes a while for it to do the final top off after an hour, it's got most of its charge. You could use at that point without waiting for it to finish charging the next charger from ebay is my favorite type. It adds an extra layer.

Let's get this one out the way, so it's not got a little obstruction back. It has two modules: it has the classic tp4 of five six. This one doesn't have that serious resistor. It's got the same 1.2 k one two, two one two and two zeros.

So it's got the same one amp resistor, that you can change, but this has the extra advantage of having the dw01a and this mosfet. Now it's worth mentioning that if you look at the tiny mosfet package on this one, because the circuitry measures the voltage in the vent of an overload or short circuit, because a smaller mosfet will have a slightly higher resistance uh, it means that it's capable of supplying Less current before that, over current trips, this one uses a bigger one. I don't know what its current rating is, but, generally speaking, the bigger mosfet packages have a lower resistance, so they will actually be able to put out a lot more current before it actually trips. The over current or the short circuit protection uh.

I shall show you the schematic for this one, and then i shall show you how to make your little charge adapter. So, in the case of this one it starts off exactly the same as the other. Without that uh resistor, though, that point four ohm resistor, it's got the same two leds with one k: resistors. It's got the same programming resistor by default, the one amp programming, but the difference is that this one then has the protection chip as well um and that drives the mosfets, and it just provides that extra.

It provides double overcharge protection, but, more importantly, in this case for my applications um, i run strings of leds and stuff off them and it stops it from over discharging it cuts it off at 2.5 volts, instead of just letting the cell go all the way down To the bottom, because if you operate the lithium cells within their voltage range of about 4.2 volts down to about 3 volts, or so it just prolongs their life greatly, and look at that one that i've been testing. It's been getting great cycles. Okay, now to get on to making your little adapter for this, you can do two things here. If you're, just wanting to jump onto lithium cells, you could put a couple of crocodile clips leads onto one of these modules on the battery output connection.

But my preference is this little arrangement here where you can put a connector in the battery, and you can then use it for powering other things via this other connector, with all that extra protection, the advantage of this one i have used it to top up cells In devices like this, when refilling them with liquids and topping the cell up, it's very important that when you do that, make sure you don't short anything out and get the polarity correct, double check the polarity. If you put this the wrong way around, it may actually blow up these modules. They might not be too happy about it. So to make up your adapter use your favorite connector everyday is a favorite connector.

These are mine, they're sort of little molexy type, connectors um. There is a name for them. Can't really remember is xh25. I don't think it is not sure, but there is a name for these connectors, i kind of like them um and make up two female connectors and one male connector.

The male connector is to plug into the battery, because by making up with connectors, it means that you can basically use it with multiple batteries. In the case of this one, i'd just not have a usb lead connected. I would just put one of these little connectors on, so i'm going to uh get the soldering iron on and i'm going to bring the bits in and i'm going to show you how to solder this up. So one moment please, the soldering iron is up to temperature.

I've brought this up closer, so we can see it better. So there are four connections on the output of this b plus and b minus are the battery connections and out, plus and out minus? Are the load connections, so the first thing i'm going to do is i'm going to get some juicy lead based solder? It's my preferred solder and i'm going to put a little soda onto each of these pads. Now you could put the wires through the circuit boards. I find it easier just to actually sew them directly onto the pads.

So let's get some soda onto these. Let's do this properly, the soda is actually going through because those are fairly plated, through-hole pads. Now the first connection i'm going to put on is the one that's going to the battery. So, following the polarity here just place, your pre terminated, stripped and tint connector onto their wire onto here and just flow.

It then get the positive and flow it on being careful not to bridge to anything in the vicinity allow to cool. Then this is my output. Connect that i'm going to be using for loads, so we want to put the negative one to the out negative. Oh get get the solder iron in here and the out positive onto the positive connection, and that is it.

But for one small thing i recommend putting a bit of heat shrink sleeving over this or wrapping tape, because if you have this floating about in your bench, there is a risk that things are going to get short-circuited. Okay, i'm just going to get this stuff out. The way i'll show you putting the heat shrink sleeving on, and then we can test this we'll actually connect the battery i'll. Tell you what, before i do, that here is the battery.

Let's get the other connector that i have handy here, which is my little flying. Socket - and i show just sorry about the swamped out fingers - the lighting is really just focused on the small area here. So when you're sold onto these batteries a couple of things to note, don't linger too long, they do have decent tabs coming off. If the tabs, which are very fragile snap, don't try soldier onto what's left of them because it can cause problems uh the one of the tabs may be copper and one b aluminium.

Sometimes, if you remove the bit that takes the solder that has out the factory you can't actually solder onto that, but just be careful, also make sure that nothing can bridge onto the the little pinched seal on these, because um they've got a conductive sort of metal Layer of foil inside so after double checking polarity take your positive connection. Hopefully this will be in focus. I think it's in focus and reflow that onto there then get your negative connection and we'll reflow onto the tin pad. Now it's important to note that these connections are not really load bearing, so i would recommend wrapping a bit of captain tape or other tape over these just to actually reinforce them to give them extra strength.

It will just make it uh. Last much longer right. Tell you what i'm going to clear this stuff out the way and then we can test this. First of all, let's get the heat shrink on now.

The heat shrink size i use is 12.7 millimeters. I think that's a shrunk size once it's been shrunk down. It just seems a good choice. If in doubt, do i do? Is it was this a good idea? Is this actually going to go through here? Yeah, it's going to go through there and just by a few different sizes, it just it's safer in the long run, squish it over the module and over the actual little usb connector.

That might be the hardest bit to go over. Okay, now use whatever you normally do to heat heat shrink. I use a little hot air. Pin it's just as part of my soldering station.

It's quiet, it's convenient, it's probably what i use it more for than anything else. I do use it for actually soldering de-soldering opponents and reflowing surface mount components, but it's very handy for doing heat shrink. I recommend the clear heat shrink simply because there are leds in this and it means you can actually see the leds. It actually helps spread.

The light around as well so you can actually see even from the edge when the leds are lit right. Technically speaking, i should be able to get a usb lead now. Oh here is a usb lead. Actually, no, let's use this.

Let's do the test properly. I'm going to have to find a usb lead now one moment please, i have the lead. I have also got a string of lights to demonstrate that this can be used to power strings of lights if you're so desire. So let's plug this into here.

This is one of these generic leads you get with random products from china. Hopefully it's the right polarity, let's plug the reading in and we'll see what current it charges at. So i'm plugging this in here, the little red led is lit, and the battery that i was previously hammering over three amps into is now getting 914 milliamps, which is a lot better. It's still not ideal.

Ideally, you would change the resistor in this to 2.2 k to actually adjust it to the um 500 milliamps for the cell, but you know what it's maybe worth having a couple of these and writing the current ratings on them. So you can charge different cells and plug them on as desired, but once you've finished charging it. You can then get this stuff out. The way use your little adapters to plug into this connector and have led lights asunder, and the nice thing is that over time, when the battery finally goes down, then it will cut off when it reaches the lower voltage.

It's worth mentioning, i put two 10 ohm resistors and series these lights just to control the current through them. But if you want uh, you can, if you you're doing something like this, you can well. This is actually a little inline adapter. You wouldn't necessarily want to just plug it straight in because that would run the leds at far too much current, but you can choose the value of resistor.

You want, if you're running leds or whatever you're running little standby work lights or anything. You can run off little packs like this they're extremely useful. Now, just before i finish this video, i shall bring in those pictures and show you specifically the resistor to change. If you wish to actually adjust that to the sort of 500 outlet milliamp level, not 500, that would be quite exciting.

So let's focus down onto that uh in the case of this type of circuit board. It's this resistor! Here it's pin two of the tp-4056. So it's this resistor here you can either put in a new surface, mount resistor or just tack on a standard quarter. Watt resistor! It might be easier just shape the leads so that they both come in, like that um and then fold it carefully over making sure it doesn't short onto anything.

With the case of this, one pin two it's this little 1.2 key resistor that can get swapped out for a 2.2 k resistor, and that is how you're charging your cells properly without blowing up your house, so go out into the streets and harvest lithium celsius stuff. Knowing that now, you have the full protection to use them properly. Good result very handy little devices.

15 thoughts on “Don’t do this! there’s a much safer way”
  1. Avataaar/Circle Created with python_avatars balmung1992 says:

    Perfect timing with this! Saw a hackaday post yesterday for turning one of these disposables into an electric screwdriver. Seemed perfect for my first electronics project.

  2. Avataaar/Circle Created with python_avatars deezel_fairy says:

    Personally I use my rc car chargers to handle all my charging needs – just need to make up a suitable charge harness.
    They're incredibly versatile chargers with most being able to charge all types of lithium, nicd, nimh and lead acid.
    If you assemble a multi-cell pack they can handle the balance charging.
    You can do a 50% storage charge if the device is not going to be used for some time which dramatically reduces cell stress so increases cell life span.
    The higher end chargers will also allow you to set voltage end points aswell – I like to charge my lithium cells to between 4.1-4.15v per cell (90-95% state of charge) which studies have shown dramatically increases the cells lifespan.

    Only downside is its totally reliant on you to set cell count/charge current correctly.

  3. Avataaar/Circle Created with python_avatars Dave Rei says:

    Great video Clive. I have used a bunch of TP4056, my only regret is they don’t have a built in thermistor/thermocouple on a lead to sense an over heating battery. Otherwise they are great for single cell applications.

  4. Avataaar/Circle Created with python_avatars Bright Spark says:

    I have used a similiar kind of USB charger circuit – albeit ones with a USB-C connector – with my modded gameboys.

    In the case of the original "brick" (aka DMG GameBoy) you can just wire the 5V output lines of the charger circuits to the battery terminals, as the system expects 6V from the batteries anyway, and the internals are tolerant to running undervoltage to that degree. I even had enough room in the battery compartment (after trimming out the battery divider walls) to stick in a QI charging coil, and solder it to the 5v input lines of the charging circuit.

    For my GBA, I had to use a 1N4001 diode to give the GBA the right voltage, and it was a snug fit, but at the end, everything fit perfectly – tho I may want to replace the hot snot I used to stick the charging board to the battery cover with resin or something down the line, as it actually melts the hot glue when it's charging because the board is getting quite warm in places.

  5. Avataaar/Circle Created with python_avatars dgSolidarity says:

    Ali Express electronics do exactly this: zero voltage regulation. A children’s gameboy-thing got the 3.7v cell up to 4.9V. They refused a refund, I fought for months explaining the fire hazard + violates the specs of the lithium cell manufacturer. They. Do Not. Care.

  6. Avataaar/Circle Created with python_avatars SteveMallison says:

    I'm so disappointed! I've not been able to find any discarded vapes at all around here, even though Malaysians love to litter. I guess it's just not popular here.
    Like the advice on how to charge Lithium cells though.

  7. Avataaar/Circle Created with python_avatars ChrisD4335 says:

    wouldn't there be a charge controller built into the vapes?

  8. Avataaar/Circle Created with python_avatars Preston Cheap BT headphones test guy says:

    You’re the one who suggested to do that in one of your other videos. 🙄

    Anything to get like and views.

  9. Avataaar/Circle Created with python_avatars ASphere says:

    This is how every high schooler charges them, since the days of juul in 2016. It’s sus, but u just do it for short periods at a time and it keeps the vape running for shre

  10. Avataaar/Circle Created with python_avatars Jarkko Kankainen says:

    There's so many connectors that are almost the same, but I think those are Molex KK series. JST SM, XH and Micro series have premade wires in ebay / ali etc. I guess it doesn't matter what you use, as long as you're consistently using the same leads lol.

  11. Avataaar/Circle Created with python_avatars kushfrom handsworth says:

    Even before you're first videos of these I've been trying to get as many of these as I could now. It's just such a big waste and it actually makes me jealous of how many are being thrown away. I've been finding them on my way back from work in the morning on the floor in the city centre by all the bars. But I don't want to look like a homeless person going around staring at the floor looking for second hand cancer sticks like the homeless people do. It is such a waste though.

  12. Avataaar/Circle Created with python_avatars Austin Hibdon says:

    doesn't the battery's ISR limit the current besides just the cord?

  13. Avataaar/Circle Created with python_avatars zodiacfml says:

    im cheap and do janky stuff but even I wouldn't do this. 4.2V is already high voltage for the cell, pretty much overcharging but allowed by the industry. China sells/give out a single cell battery charger.

  14. Avataaar/Circle Created with python_avatars Andrew Currie says:

    I have been using these found cells with the PIR sensors/RF sensors to make battery operated auto sensing lights. Along with these charger boards.

  15. Avataaar/Circle Created with python_avatars Nino Joel says:

    also if you ad a small heatsink to the TP4056 you can increase the charging current dramatically

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