Five years ago, I took a look at our eBay charger that was just like this one looked almost identical, but the circuitry and it was absolutely criminal. it was Dire and I thought I'd buy another one partly because I wanted to see if the circuitry has evolved and partly because I thought this would actually make a really good case for your own trickle charger because uh, it has the spring-loaded contacts will accommodate double A and Triple A So if you saw my other project, I'll just make loud springy clicking noises. If you saw my other project on making a USB trickle charger, it may be viable to actually make a version that goes into this, or even modify this one. This feels slightly warmer in the back to actually operate differently now.

I've got a meter here. we shall Zoom down this I shall Focus down roughly on there just so everything's a little bit sharper. and if we put one to sell in, the current is about 176 milliamps and you'd think that if it's fairly standard circuitry, it would roughly B. Well, let's try different cells and see what they show.

175, 175 and even the Triple A 172. So you know it's quite a lot of current to trickle charge continuously at Triple A. However, if you take that figure uh, 107, let's say 177. it says it won't.

Okay, so that's 177 milliamps times four equals you'd expect to go to 708 milliamps Under full load. but when I put them all in, it actually only goes to about 450 milliamps. So I'm not sure what secret is in here. They're using a common shared resistor or is it just the resistance of this cable that's affecting that? I Mean it's not a bad thing.

It means that as the number of cells goes up, it's going to put less strain on your power supply. Not that you know, half an amp, or even if it had been the 700 milliamps, it wouldn't have been an issue. But anyway. I Digress: Let's do what we're here for and whip the back off it.

It's that screwdriver going to fit. Oh, it's barely going to fit and we'll see what's inside. and if it's improved. I'll tick that.

I'll take my precious Posh nickel metal hydride cells out first. this is designed for nickel metal hydrate or nickel cadmium if you still have any. Trickle charging isn't a bad thing, but it's not something you want to leave them charging for long periods of time with a very high current. That's why my version only charged about say 20 milliamps or something like that.

I can't remember how to charge that. Let's see if the circuit board is different. Let's see if it explodes into pieces when I take it apart. No, it doesn't.

So one circuit board not seeing a lot on it. Nothing on the other side other than the LEDs which I've just nudged out of place. And the contacts. Here's a little springy.

Negative contacts. Um, really dodgy soldering up here, right? Tell you what, Tell you what, I shall take the usual picture and then we'll explore it and see if this is hackable. One moment, please and resume and this circuit is much better. I'll zoom in.

This It's quite a wide circuit board, though. it's going to take up all the space. The incoming Supply goes on to these rather splodged contacts. Notice the copper looks like it's lifted just with the heat.

It's a very cheap and nasty circuit board. It's very cheap and nasty product. they've soldered this wire on, but then out of impatience, they've kind of let it go before the sodas. uh, cool down completely so it spread a bit.

Doesn't really matter. Look at the positive coming on here and we get the negative. Just going around to all the negative contacts of the cells, The positive goes to these two resistors in parallel, both roughly 5.1 ohm. This one is strangely accurate 5.11 Ohm 5r11.

And then there's a B tiny one with the same rough value 5.1 Ohm I'm not sure why there's two different sizes and then it goes to a common positive bus that has a 18 Ohm resistor going to the positive contact for the main current and then a 150 Ohm resistor one five, one one five and one zero in series with the LED. Then also going to that contact and that is distributed four times. Let me show you the schematic. Here is the schematic and I Have to say I Got a bit of Deja Vu here from the previous design.

we have the two parallel resistors there, one big and one small that's probably that got warm earlier on. And then we've got the 18 ohm just passing current straight down to the cell. It would have been nicely put down here, even one diode here because when you plug it into a USB power supply, if you unplug the power supply but leave it plugged in, these batteries will gradually discharge back through this resistor. and these ones um, and the usually USB power supplies have a a fairly High ish value resist across them, but left for long enough will basically discharge all your cells.

That's a bit strange, um, but most of the current flows through this 18 Ohm resistor. That's what sets the bulk of the current, but there's also current flowing through this 150 ohm uh resistor and the LED to make it light up. And that shows you. when there's a cell in that position, there's no fancy monitoring.

The LED will not go off when it's charged. All that will happen is that it just keeps trickle charging all the time. And with standard Nicom metal hydride cells, it's not recommended to charge them at very high current all the time. They're okay for a short period of time, but if you do, what happens at the end does the form gas bubbles on the electrodes, and although those can convert back into the electrolyte by a chemical process inside, it does result in higher pressure and it can result in slight loss of electrolyte.

It's just not ideal for them, but it's fine at low current and that means the easiest fix here excuse me is to get rid of these 18 Ohm resistors. just basically just chop them out and then you could actually just have the 150 Ohm resistor. or you could increase those if you wanted and that will turn it into a very simple trickle charger. Replace that with a diode over there and that would fix that problem as well.

Um, and I got Deja Vu here with that previous designed I looked at it I looked up, took a b screen grab here and the screen grab showed the Hideous circuitry. There's a 2.2 Ohm resistor and then there's a 20 Ohm resistor feet in the batch and then they just stuck the LED in without any current limiting whatsoever. So in that previous design, the current through the LEDs was ridiculous and at the end of that video, I kind of Drew This little bit here that said, this is how I'd have done it. The resistor there but a resistor in series the LED and that is what it is in this design.

Where are they inspired but their original video or is this a completely different charger? Who knows. But the answer with this set here is that simple thing that these little 18 ohm resistors just to get Soldier yarn and slide them off. You know I'm going to do that right now one moment please. The soldier iron is now up to temperature.

I've got a cardboard box here 3dqf 3D Quality filaments Philippines are actually made in the UK and they seemed quite good quality. I Just thought I'd mention that not a sponsor. It's what I've switched to using and the first thing I'm going to do is I'm going to remove those two resistors here at the input, the big one and the little one and all I'm doing here is just slide them off. Oop! I completely failed to slide that one off and ping them to the side.

Then I'm removing all the little 18 ohm resistors that are passing the highest current. so just wipe them off again by sprucing some Soldier on them and then using the solder under. Just basically swipe them off. That's one advantage of surface mount components.

these little ones. You can basically get this solder iron on both ends at once and wipe. Okay, now I do have a shot key diode. I'm gonna have to use a magnifying glass to make sure I've got this shot get down the right way around.

But what I'm going to be doing here I'm going to be using my magnifying glass to check, but there is a little splash of solder. Note: It's fine although I definitely moved those resistors completely and not stuck to the circuit board somewhere. I'm going to put up the diode here and the shortcut out. Yeah, the little band is there.

Wire shot, get out. No particular reason. Um, it's just what I had handy. So I shall be doing it trash.

Style But I put a little bit of flux on there, sitting this on and just basically splishing one end. This is where I will screw up I'll also block all the light from the bench lights if I get one end stuck. that's usually a good start and then we can just squish the other one down while they melt the other end. Very professional.

Yes, there's no finesse with uh with surface mount. Oh, this is not going to come. Let me just get a little bit more solder in there. Maybe I should actually squish that one across a bit.

I think I will squish that across a bit just to make more room so get a better connection. There is no choice. You have to use surface mode these days. I Defied it for so long, but now there is no choice.

and to be honest, I'm not too bad. It's actually quite Pleasant to work with. Actually, that's nice. So once I've done that and let it cool down, I'll just reflue it.

time to touch a solder on the other end and that will be it in place. No theoretically. if I remove this out the way, how to plug it back into the tester? When I put the cells in, Uh, the current should be much lower, it will be probably about 15 milliamps. I'm not sure where is the power supply.

There are numbers all over the power supply because each time I charge it I write the capacity that went into it. So at the moment showing zero current, pop a cell in LED lights up. it's showing 10 milliamps. That's how I do was a trickle charger.

That's all right, and it should can assure that for each and every single one of these. So it's now up to 19 now up to 29 and now up to 38. So roughly 10 milliamps and all the current is now going through the LEDs to show you that on the drawing. and since I've removed, moved those and I've put the diode in here is a little shot.

kid out I should draw that in as a little shot key diode. The current is going through the shortcut diode and now it's going through the 150 Ohm resistor and the LED straight to the cell. and that means that it's not going to reverse discharge into the power supply, use it with or power bank or whatever. Um, and at that current, it's just going to be ideal for topping cells up or just leaving them on a permanent.

Just a a gentle trickle in the background so they're ready for use and fully topped up to the hilt. It means that I sell this size. What is this one? 2 000 milliampere that would take like yeah, that would take a very, very long time to charge if you actually trusted it. If you wanted to charge it completely, it's more for topping up.

This would also be very good for rescuing uh, cells that your smart charger didn't recognize because when you put them in here, it doesn't care what voltage it starts at, it's going to boost it up and actually get it back in action. So uh, the power supply in short has improved and it's extremely hackable. I'll put my little tub of top Nick RF 800 uh flux. Just a generic cheap flux.

Sword streams with my polish sellers on eBay in the UK ceramic trees are strongly recommended. The main thing is that because they're not metal, they're very heat proof and they don't stick so badly to components. They're doing magnetic effects. Uh, but they do get resin on them and when they get resin rosin on them the flux.

they do get a bit sticky. you have to clean them every so often. I'd say that's a success for the conversion that I wanted to do and that is basically just converting this from the original fairly High current uh charger into just a basic little trickle charger. ideal for just topping cells up, so that's a good result.