Well, isn't this just the cutest little thing ever? It's a power bank. A solar power bank that is wearable as a keychain and it's designed for micro USB You can recharge it by micro USB or indeed in the sunshine apparently. And it has a micro USB out and the solar panel. It does appear to be connected because it's doing that obligatory thing that if I point it at the light here, you'll see the red LED gluing there.

and when you plug it into a suitable testing device, where is the correct connector for here? let's plug it in here it Powers up. Let's Zoom down in this. and if I stick in a load tester and start cranking the current up I might get the right thing here. Yes, I am.

It holds its five volts 700 milliamps starting to drop off a bit, about 800 milliamps. Oh, and then it cuts off. So let's say it's rated around about 800 milliamps or so. That's okay.

I wouldn't really see you charging your phone with this, but for charging things like a little flashlight, it's not that bad. Compare this and I've tested this, it arrived flat. This isn't uncommon for these things because uh, they do tend to have the uh, they do tend to have the five volt output all the time. If I unclip this just to make it even smaller and we compare it next to Poundland's non-rechargeable 600 milliamp one and this one came in.

It was rated 600 milliamp and it actually tested in. at 600 milliamps, that's pretty good. Let's try and Spudger Opener. The question is, is it glued shut or is it Scrooge Shot: Are there secret screws underneath this solar panel? Let's try.

open this up. I'm noting a little plastic insert here that almost suggests that they designed it to have multiple different uh sockets on it. I think this is glued. that's going to be so destructive.

Oh I've almost feel guilty, but not that guilty. Um, oh nope. Nope. hold on.

that is cracking he said stabbing a spudger into something with a Lithium cell inside it. Quite a compact thing. Lithium cell. Now is this going to have? Let's get some isopropanol and squirt it around this solar panel and just see if there's hot milk glue under there.

and if this liberates it by wicking in. Is this going to help? I Want to actually test the solar panels? I Don't really want to destroy it, it's easing up. Are there any screws under there? Oh I think there might well be I think there may be screws underneath this, but I could be wrong. I've only just seen a little glimpse of what's underneath and it's not really actually coming out too easily.

Oh, there's a circuitry. Quiet, complex circuit board that is ludicrous. Look at the circuitry on that. Okay, right.

That means uh. this. The actual Lithium cell is occupying just basically the lower half. They could have really left the solar panel off since it's not actually doing much.

Is it all right? Let me see. what can I do here? This really is glued together, isn't it? This is not going to end well and that is coincidentally where the Lithium cell is I Don't think this is going to compart too easily I may have to squeeze it in a vise to try and crack the glue one moment, please. The vice of knowledge is failing to provide the desired results. I think I may have to get extreme of this and since it's already started cracking I may just crack the plastic.

That's where you're going to get reload microphone pops there. We go there, we go. and let's see if I can fit the solar panel through here. Yes, it does kind of fit through here.

largely helped by me breaking the plastic. What do we have? Can this come out easily enough? Yes, it kind of kind of can. I think I think it requires a bit more isopropanol to be squirted around the lithium cell under here? Hmm yeah. I can see a little glue pad.

The one thing I hate about doing stuff like this is it tends to pucker up the case of the cell a little bit where other cell contacts. There we go. The cell is a metal cased cell. That's unusual, right? Tell you what? I'll take a picture of this and we can reverse engineer and see why.

Is this circuitry so complex one moment? please? Okay, it's time to export. That was quite hard to reverse engineer I Have to say it was a beast and for reasons so. This is the back of the circuit board. mainly a set of negative ground plane but not the negative the battery.

It's after the protection and then just a few sort of buses and links. So going on to the main side of the circuit board, the bit that's interesting, let's zoom in this: Let's Get Closer because well, let's face it, there's quite a lot on it. There is so much on it, lots and lots of transistors that it turns out are all entirely for controlling the LED It makes you realize that the modern power bank which just is a little chip like this, an inductor and a capacitor. That's what it is now, but this one has a date in it 2013.

that was New Old Stock that was being sold. The lithium cell itself uh does carry a charge capacity of about 500 milliamp hours so far. So the main thing is worthy of note. Here are this protection circuitry down here, the Dwo1 and its mosfets, and a very unusual connection to one of the mosfets.

Uh, we've got a little boost circuit here I failed to identify this chip. It may be because the age. all the modern similar Bush converters with the little inductor for boosting the voltage up usually use pin 2 as the negative and they all have a fairly common pin out. This one did not fit that comp pin out.

Pin three is negative. The two inputs for charging. We've got the Um main diode and a 1 ohm resistor for the USB input going straight to Lithium cell and the solar panel goes just via diode and realizing the current limiting of the panel itself. Uh, what else can I say here? Not a lot.

I Think we should just cut straight to the schematic. That is the best bet here. And here's the first part of three parts of the schematic because that's how complex this is. foreign.

So the two inputs are the USB going via that diode and that resistor straight to lithium cell. The solar input is inherently self-current limiting because the little solar panel quite respectable I Have to say each of the lines on it represents one panel in here one cell. So it does actually add up to about five or so volts and it's capable of putting out when I hold it up to light up. here.

It puts out about 20 to 25 milliamps which is impressive, but all that current goes straight to Lithium cell. and the only thing that regulates the charging is the Dw1 protection. So as soon as that reaches 4.25 volts, that's when the charging cuts off. It's worth mentioning that there is a little chip facility here.

Now Is this a current regulator? Is this? possibly even a charging chip? Uh, that was designed to Um charge a control current. There is a little resistor there that could have set that current to the capacitron output. This may have been Uh Lth7 type chip for programming for a programming current and actually charging the Lithium cell in a more controlled manner. Not sure that would have negated that one Ohm resistor and then it would have gone through this.

Interesting. Maybe I should check the pin out, but having said that, that's a fairly modernish chip I think and this is an old circuit. but anyway, the charging happens with these diodes, uh until the cell is completely full. The inputs both also feed this Led via this transistor.

this PNP transistor that is normally held on by this transistor being turned on and it's controlled by the Dw01 the Uh charge protection chip. So normally the current will flow or say from Solo or USB through an appropriately size resistor. 1K for the USB and a higher value for this solar just to actually reduce the draining of the current and that goes uh to the LED via the transistor which is normally would normally be held off by this pull-up resistor because it's a PNP transistor but is pooled down when that transistor is enabled to allow the charging light to light. and it means that when the charging is complete and this turns its mosfets off, it actually turns this transistor off as well.

Um, and then this uh all transistor also turns off, It's all level shifting. The other thing that can make the LED light is via this one key resistor here from this transistor and that transistor is controlled from the output from the Boost converter that turns this transistor on, which then pulls the base of that transistor down. That lights that Led. It's so complicated, it's just ridiculous.

Compared to Modern chips, it's a a crazy little thing, right? Let's take a look at the bus converter. these strange boost converter. So here is the Lithium cell with its protection of abbreviated protection. but I'll show you that in the next page: the Bisc Converter Mystery Chip I've written the numbers on, so three is ground, six is the sense input, the four is the switching one to the coil, Uh two is the output to the LED control circuitry, and one and five are presumably.

well, one of them is going to be the Power Army I Guess one could be wrong and five may also be an enable input. and stranger, they're powered from the output so that initially current will flow from this Lithium cell. it will go via this inductor and that diode and then it'll find its way back and it'll power the circuit with its own little decoupling capacitor here. But as soon as this kicks into action, it goes up to five volts.

It will give itself a more solid power supply I Wonder if that was just to give it a stable 5 volts? So this starts pulsing the inductor at high frequency as needed. It puts a inductive charge on the inductor turns off that collapses, basically adds on to the voltage that's already there. goes through this shortcut and charges this big cluster of capacitors. The cluster capacitors is actually notable.

They've played safe, they've got a little tantalum beaten. They've got two Ceramics a big ceramic one and a little ceramic one all in parallel to deal with General storage and high frequency efficiency for just the ability to grab those sharp pulses and then hold them to actually transfer them into the higher impedance capacitors. The USB Output: The five volts goes to the USB output. There is a 0.1 Ohm resistor.

Um, but it's of no I'm not really sure it's not. It's not being used as a cinch resistor. I Can't see anything that would suggest that. Other things worth of note: there's a 220 uh K resistor which feeds one of the pins from that peels one of the pins down to negative and also the two pins on the side.

Well, this pin and one of the pins the other side are just linked to give that sort of a I am a power bank type Vibe and uh have stuff draw about an amp I thought I don't think this can deliver a fill up. The feedback circuit is to fairly precise precise. Resistors: a 67d resistor which is 487k and Uh 150k which is 18d. That is a standard value of resistor though the 150k and what that does is when this reaches 5 volts, it will deliver the threshold voltage probably about 0.6 That tells the Bush Converter to hold back and once that voltage drops again, it will start boosting the voltage up again.

That is that. Next I have to switch to the next notepad because I ran out of space on this notepad. That was the last page. I Go through a lot of notepads and it looks like a standard Dw01 protection circuit with the two mosfets two mosfets.

because mosfets have an inherent diode in them that it can bypass them and current is flowing in both directions for charge and discharge. So in the case of that this the charge mosfet overcharge or over discharge. When it turns off, this mosfet, current could still theoretically flow through this protection diode even if this mosfet was off but would be blocked if this moist fats off would be blocked by that diode. And likewise from your charging and over discharge turns off.

Or should it say if you're discharging over discharge turns off. Uh, it will turn off the that mosfet but it will be blocked by the diode. Um, the other thing to note about that is the two mosfets. They will conduct in both directions.

It's just uh, they're more efficient at doing a particular way and the diodes are also a factor in using them in a particular direction. There's a Lithium cell. There is the Uh 100 ohm resistor and 100 nanofarad capacitor commonly used to get a sample of the voltage across the cell and filter it so that if the output this one in use would be jittering a lot because it would be driving the high frequency Um, that would be getting noise from The High Frequency boost circuit. So what this filter does, it just gives it a more stable voltage so it can monitor the voltage level and turn off the mosfets if the voltage starts getting low.

The 2K resistor here is used to detect a short circuit or a high current. It measures the voltage from the zero volt rail here over to this side of the mosfet. So if it sees a significant voltage drop across the mosfets, it will trigger the protection. So when you see a high current protection circuits, they may just have bigger mosfets or lots of mosfets in parallel.

That increases the current, but it also increases the Uh. It also lures to say the unstate resistance so that it takes much more fault current to actually cause that voltage differential here that trips this. And and here's the Oddity this little arrow here because when it detects that the Lithium cell is fully charged up and it turns this mosfet off, it's also turning off that. Let me just grab that back in again.

it's also turning off this transistor which is connected directly to that, which then turns off that transistor. and even though solar and USB may still be present here, uh, they can't then light the LED That's all it's done. It's basically stopped them from lighting the LED Very retro, very strange old-fashioned thing. I Mean it works.

And the nice thing about it is that because it's a bit dumb. uh, it, uh, just puts out five volts all the time, which is Handy uh. useful for charging things like these little lights. you know that, um, are just they've got fairly small Lithium cells in them, particularly if you could just plug it in into the key ring, just leaving it hanging on the hook where you'd normally have it.

Uh, One other thing worthy of note that caught me out: I was looking for which circuitry was doing this and when I connected the battery for testing. Uh, the unit was not putting the 5 volts out on the port here and I thought one of these was going to be a latch because it's only when you charged it that it did that that it actually started putting the five volts out. In reality, it's the Dw1 that's doing that when you, uh, basically connect a Dw1 for the first time. or if it's been uh, over discharged or there's been a fault that's caused a brief short circuit that's caused that trip, then it will actually stay off until you apply current to It Again by putting the charger in and that's what wakes the circuit up in shipping.

If the last thing they did was connect the battery um, then the this circuit would have been in a dormant State not drawing any current until you receive it and you put it in charge and then it would top the seller. but it would also activate on the circuitry because it activated the Dw1 protection chip. Pretty neat really. There's a lot to be learned from the old retro circuitry.

Um, this is how it used to be done. Now it's done by one time load chip and doctor and a capacitor and that is pretty much it. It's amazing how things have changed. It's a pretty neat technological advancement.