In a recent video, I showed how you can reclaim Lithium cells from various discarded electronic devices and you can recharge them using these very common Tp4056 type modules. Now a couple of people got in touch and said that you can't power things from the Lithium cell at the same time as it's charging or it will simply Never End charging and it could potentially overcharge the cell. That's the reason for this video because it's not quite right. This this thing will not overcharge the cell, but it does look like it keeps charging.

Now to explain that in a moment, but let's take a closer look at this classic TP 4056 board I say TP 4056 board. In this case it says Tc4056. It could go under loads of different names and you also get the little six pin version tp4057r Lth07. Just loads of clones of these chips.

But here's the basic principle: 5 volts comes in in the USB port and in this case, it's following the data sheet currently by putting a point Forum resistor to the supplier to the chip and then there's a decoupling capacitor in the input and one in the output. for stability. there's two LEDs sometimes ran green, sometimes red and blue with a 1K resistor each to indicate the charging status And also very importantly, this little resistor down here which sets the charge current by default. These modules are supplied with one two two that's one two and two zeros 1 200 ohms or 1.2 K and that typically sets a charge current of one amp.

It's worth mentioning that the way these chips work, they actually limit the current internally as like a linear regulator. So these will get quite hot if the uh if the Lithium cell, particularly if it started at low voltage. this actually acts like a resistor and it will get hot. and if it gets too hot, it will then self-regulate back.

It'll turn the current down itself to a controlled level and the output then goes up to 4.2 volts. and then the LED changes to the charge state. But there is one other thing that you should know. you're not just setting a one amp current uh, limit.

With this, you're also setting two other 100 milliamp thresholds and I'll show you that in a moment. But let's take a look at the more upmarket version of this which I like I mean these are cheap. These are dirt cheap. These are the circuit boards that if you buy them on eBay then buying one will cost pretty close to buying a pack of five or ten because of the postage.

That modules themselves are really cheap. This is the same circuitry. It's missing that input resistor, but it's got the two. LEDs It's got the decoupling capacitors.

It's got the current setting resistor down here. I Really do wish they'd put a round pad here and one here that would let you put a standard through hole quarter watt resistorant. It would have been really handy, but this one is the extra feature that it's got. uh, the Dw1 protection chip.

Which means the main advantage to this is that although this chip isn't going to charge above 4.2 volts, this will act as a second layer of protection. Plus, if it discharges below uh, three volt set down to about 2.5 volts, the Dw01 will kick in and this mosfet will switch off and it'll turn off the battery so it's not discharged too low. Not really much of an issue when you're driving LEDs directly because the LED forward voltage is typically about 2.5 volts. But let's take a look at an example of this and why.

It may appear to keep charging but doesn't keep charging and I shall Zoom down a bit more on this. Let's see if I can zoom down a controlled manner without going all over the place. Different camera from normal, a bit trigger sensitive in the zoom button. Color is also a bit different from normal and so is the sound.

I'm in a different location at the moment, so when you set, I'll show you in this graph here which has voltage and it has current. When you set with that resistor the one amp threshold, you're also setting a threshold one tenth of that. So it's 100 milliamps. If you'd set that 500 milliamps, this would have been 50 milliamps.

but in this case it's a 100 milliamp threshold and it's used at two stages in the charging. It's a very clever chip. In the case of that, using one of those modules and connecting some LEDs with a 10 Ohm resistor, the current here would be typically driving the string of LEDs. It would be about 170 milliamps with a fully charged cell when you start charging.

If the voltage is anywhere below 3 volts, the Tp-4056 will initially start trickle charging the Cell at 100 milliamps. So even if the cell had been completely discharged to zero which is not usually recommended, but does happen and doesn't instantly mean the cell is destroyed, it's not. It's not great for it, but it's not going to be the end of the world. Not recommended for high current applications or like tool batteries.

You don't really want to use a battery at super high current if it's been down to zero volts. but if supposing it was at zero volts, it will trickle charge the cell until it reaches about three volts. Once it reaches 3 volts, the current switches up to the one amp and it will continue charging up until it reaches just above four volts at one amp. But then instead of just suddenly shutting off again, the voltage tails off gradually at the end until it reaches the 4.2 volts.

And roughly, but more importantly, it's monitoring the current. And as soon as the charge current, which is gradually getting lower and lower, as soon as it reaches the 100 milliamp threshold again, or the tenth of the charge threshold, it will suddenly cut off I'll just continue that on so you can see it cutting off. So what actually happens when you put LEDs across? if I was there? if I had LEDs connected drawing 170 milliamps, what would happen is the charge would get to the end and it would gradually tail off. but at this point here it would uh reach roughly the Uh 170 milliamps had been was being drawn by the load and it would then just basically be powering the LEDs and the voltage of the cell would be just margin below 4.2 volts but it would never quite go higher because this is limiting the current it's going straight to LEDs It's effectively powering the load, but that means it will never reach its end of charge indicator point and it is just the LED indicator in this instance.

so it'll just keep putting current out and it will just look like it's charging all the time and the battery will be charged up to its full capacity. almost. But although it says it's charging still, it's never going to charge that above 4.2 volts, it's just going to power the LEDs directly. There is another scenario here supposing I change that to a 100 ohm resistor.

so the current was now about 17 milliamps through the LEDs. What actually happens there is that the module charges the battery up and it does terminate because it reaches the point that it dropped below 100 milliamps because the LEDs are only drawing 17 milliamps. So top the sell-off until it reaches that and then it will cut off. The LED will change over from one to other, but then at that point it's turned off the charging.

The LEDs will pose that slight load, the voltage will gradually drop again until it kicks back in at the threshold and it tops it back up to 4.2 volts. and then it slowly starts to charging. So in that instance, these LEDs will just toggle back some forwards really slowly, just topping the cell up each time. So uh, that's why it looks as though it doesn't end end the charge, but it's not charging above 4.2 volts.

It is still keeping it well within its rating. So these are very useful modules. I Use them quite a lot. I'd Recommend if you're using Lithium cells at all that you get yourself some of these modules because they are extremely useful and of the two I have to say this was the traditional one I'd Kind of recommend getting the one with that extra bonus chip on it, the Dw01 and the Dual mosfet that just acts that as an extra layer against chip malfunction for overcharging but also protects a cell against over discharging.

It means that even if it does discharge down to the 2.5 volts that this cuts off. All that will happen is when you start charge it again, this chip will go into its initial trickle charge mode before switching to full charge mode and bring it up to the top again and that is it. It's also worth noting that because the way these chips work, sometimes you plug something and you think oh, is it not charged yet Well, there's a good chance that if you've left it on for say an hour and it was a one amp hour cell, then it is pretty much fully charged. but it's just finishing off that little bit at the end.

But to own tension purposes, if you just unplugged at that point used it, it's going to be charged over 90 percent of its capacity anyway and it is ready for use even if the indicator lights haven't changed. And that is the myth. Busted on the Tp-4056.