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A gloriously dumb USB powered NiMH and NiCad battery charger that will guarantee a full charge every time, but only if you're not in a rush. A trashy 500mAh cell will take about a day to charge, while a luxuriously high capacity cell could take most of a week to charge - but will be charged right to the hilt and not be harmed in the process.
The unit uses low current trickle-charging at between 20-30mA to ensure a safe charge at a low enough level to allow the inherent feature of self catalysis of end of charge gas bubbles back into liquid electrolyte with low pressure buildup.
Can also be powered by a 5 or 6V solar panel and will use whatever solar energy there is to put some charge into the cells.
The PCBs can be cascaded with a common power buss to create an array of up to 40 charge positions from a common 1A charger.
Each cell is charged completely independently from the others and has a diode to prevent backfeed when power is removed or there is no solar power available.
Individual LEDs to indicate charging status. Choose whatever LED colour you like. Power indicator LED is optional and can also be any colour of LED.
There are four 3mm mounting holes for feet or for mounting the PCB to a panel. I'd recommend against having the panel loose amongst metalwork on a bench in case the back gets shorted out.
This trickle charging system is perfect for the newer NiMH low self discharge cells. It's basically creating a better than fresh-out-the-pack level of charge.
Here's a link to the gerber zip file for getting PCBs made. YouTube prevents a direct link to a zip file for security reasons, so you will have to copy and paste the link into another browser tab.
If you enjoy these videos you can help support the channel with a dollar for coffee, cookies and random gadgets for disassembly at:-
This also keeps the channel independent of YouTube's advertising algorithms allowing it to be a bit more dangerous and naughty.

Some circuit boards have arrived, and that means it's project time. These came from a manufacturer, glc pcb, but i paid for them, they're, not sponsored. So i can say what i like about them. For instance, this strange skid mark across them.

The lack of the screen print in that particular area and the slight divot out there that's what i can say. That's what it's like when you order circuit boards for real. Let me just put the others out the way we only need one. So this is the sweetest dumb usb powered nickel metal hydride charger and it can recharge, recycle pro.

It can recharge sony cycle energy, it can recharge, panasonic cells, kodak, poundland or dollar store cells. It can premium eneloop cells, it can charge the ones you get out. Your solar light and it can charge nickel cadmium and it doesn't really matter because it uses the dumbest charging technique possible. It uses low current trickle charging.

So what we've got here well i'll show you. The schematic here is the schematic uh usb power in a power led and sears, the 470 ohm resistor, and then every single charge circuit is just a diode to prevent it self discharging into other cells or into the power supply. A 120 ohm resistor an led to show its charging and a 120 ohm resistor and the cell under charge, and the point of this is that the dumb chargers will just keep trickle charging it. So a really high capacity cell.

This one is charging at such a low current. It could take literally a week to charge one of these cells, but it sits in the background. It consumes virtually no power, so it doesn't really matter and it uses a thing that nickel metal hydride and nickel cadmium cells have called self-catalysis when the batteries are fully charged. Bubbles of gas form on the electrodes, but there's a chemical reaction occurs inside that converts them back into electrolyte on an ongoing basis.

So you can keep trickle charging these. You can't do that with nickel metal with lithium cells, but it'll work with nickel metal hydride nickel. Cadmium - and this is one of the softest gentlest chargers and it will take your batteries right up to the hilt - it will charge them more than your smart chargers will which often terminate the charge prematurely. So, let's start putting components in this.

So the first thing i'm going to solder in is the charge port, which is micro usb for those who are about to say why don't you use a usbc? The answer is, the usbc requires a couple extra resistors and it's a not as simple as micro usb, which has two little pins here in this particular connector. It's the easiest one to actually use now. It's worth mentioning this connector probably came from aliexpress. You can get from other sources you get from ebay, but the one problem i've noticed is that the pins, the little panty wings, that fold down and solder through the circuit board, some of them are very, very short and the short ones are not great because uh, The bigger the pin, the better the hold fundamentally because this is a single sided board.

It wouldn't be so critical if it was a double-sided board because you could have plated through holes. That would add extra strength and the pads on top. But i'm going to sort of these, i should mention this is a prototype. I have not tested it yet you are seeing the actual test and here the pins coming through from the back uh.

You know what i could test this right now. Couldn't i i could test this by actually plugging a usb lead into it and checking that what i think is going to be positive is positive and what i think is going to be negative is negative. So, let's turn this to 20 volts. Let's bring in a usb lead from the vicinity, let's just stuff it into here and see if the projects got off to a good start or a bad start.

So this is going to be positive. This is going to be negative volts. That's perfect! That's a good start if the video already sounds a bit abstract it's because it's wine powered slightly cloudy wine. It's ebay wine! As in like a kit from ebay, add sugar and yeast bang it into a demijohn and make wine in about a week.

It's pretty good! No hangover, yet this is a good thing right. Okay, so let's put the resistors in the resistors 120 ohms each there's also a diode i've preformed these uh, the best way to form them is one of these things from ebay that has different positions for the different pitches of the leads and then different, spacing for The component size and you pop it into the one that fits and you fold the leads down and crop them. That's it's a very handy tool. I'm not sure what it's called, not sure the searches for it.

They appear to just appear and disappear on ebay. Randomly. I'm not sure why so, let's put the diodes in the diodes are 1n407s, because that is what i have. You could also use 1n401s twos threes, fours, fives, six or sevens it's just a generic one, amp diode.

Technically speaking, i could used a one n four one. Four eight, which is a 100 or 200 milliamp diode. It doesn't really matter uh. It's only seeing a couple of tens of milliamps.

Let me zoom down on this, so you can see it better. Let's start by soldering those in so i'm going to use a julian alety type sort of technique here and use sticky tape over them. I think that's. What julian does not really sure here is insulation tape, i'm going to stick those diodes down with tape, i'm starting with the shortest components.

First, as you always do just because it's easier and use gradually bigger and bigger components that stick up further. I used ridiculously big pads on this project because i could - and i used huge tracks as well. Other things worthy of note. If you wish to make a big bank of these from one usb connector, you can put the usb connector in the middle one, and these pads negative and positive will let you just spread out along other boards, because the current is super low.

It's only 10 or 20 milliamps per battery position, so you can run quite a lot of these boards in tandem and in parallel, the big pads also just make it easier to solder. I find it irksome that many of the printed circuit board design packages online seem to encourage using super thin, pads and tiny. Well, super thin pad tracks and tiny pads. That's not needed, bigger, pads and tracks are better, the more copper the better.

I could have checked these were level first they're level. They're fine. Are they pointing the right direction? Yes, they are just double checking right: resistors, uh, 120 ohm, resistors brown, red brown, one two and one where the one is a zero one, zero for a multiplier. It just lets them fit a lot of color codes in a small space.

Technically speaking, i should put the resistors in first before the diodes, because the diodes are very tiny bit bigger than the resistors. It doesn't really matter, though, even if they stick up a bit. I'm not bothered it's a very, very simple design and a very useful design. If it works, i'm sure it will work.

This is the wrong value of resistor. That's for the led. The power led, which is a 470 ohm resistor. Let's not mix them up for those people who are colorblind, don't worry about it because there's certain resistors, we get that even us fully color sighted people, particularly the metal film blue resistors, the colour bands, are so awful and so hard to distinguish in a blue background, Particularly if it comes through the actual, like orange, looks brown, basically that we have to measure them.

So if you're you're color blind, don't let it put you off things because it really doesn't matter just test the resistors. The meter keep them all in boxes of the correct value and you'll be fine, don't let it put you off. Electronics, color vision is not actually needed for electronics. It makes it easier in a way it lets you spot things, but it doesn't really matter.

Even if you make a mistake, you put a wrong resistor and you'll soon spot it, because something won't work, then you can fix it. This is such a pleasant and easy circuit board to make. I shall include the file a link to the zip file down below. In the description, then, you can make one yourself if you wish that's assuming it works in the first place.

These big pads actually feel really good, so do the to flow the soldier onto i'll just stab something with a soldier in there. Yes, i did it's fine. It deserved to be stabbed, it was actually a rival sword, iron. It was the uh vape battery powered mini soldier iron, which is actually pretty useful.

It's heats up so quickly that it's useful just for doing a random extra solder joint. Just when you know you need to blast a little bit of soda onto something, but you can't be arched waiting for the solder iron to heat up, not that's a problem with modern low mass solder irons. This is not. This is a yahuwah which i recently well today, uh it played up recently and it was just a bad connection to plug uh.

I put some uh copper ease, heat transfer, grease into the tip thinking that was going to help it created quite a lot of smoke. I don't think it's actually done much, but not to worry. It is what it is while we're here. Let's stick that 470 ohm resistor in for the power indicator led and at this point all we have to do to complete this project is add the battery holders and the leds.

I have twisted this soda in a convenient and inconvenient way. Not to worry. I shall untwist it so this is where i burn my finger by holding a resistor in while soldering its connections uh and other connection. No, that one is held in place, joy and crop all the leads with these cheap side, cutters from ebay, so common uh go on ebay and search for electronic side cutters, check the boxes, price, lowest cost and shipping and you'll find them just for a couple of Dollars or three dollars or something like get yourself a couple of sets because they're just a disposable pair of side, cutters and they're perfect for electronic use, very common because well, let's face it.

Uh, the chinese use a lot of them in the factories and it should be treated as a consumable, particularly if you abuse it. I'm just sweeping off all the copper ends here. Right leds and i have chosen to use warm white leds for the power indicators. Well, not the power indicators, but the charging indicators.

I was going to use pink ones and i thought that's overtly camp and it might alienate some people, but you can use whatever you want. You can even use color changing ones. The power indicator led is going to be a color changing one just because i can and because you're building this yourself, you can make the leds any color. You like there is one slight thing here: if you use a gallium arsenide led that's a red one for the charge indicator uh.

It means that the unit will produ will actually charge a slightly higher current which, but not much are current, because they've got a slightly lower voltage forward voltage. I could have cropped. Those leads down before i did this, but i didn't do. I have any regrets.

None whatsoever every led could be a different color. If you wish it's your call entirely, i am holding the circuit board and holding the led in and feeding the solder. In with one hand, i just want to point out that i didn't realize i did this until people said wow. How do you do that um? I don't know it just kind of happened.

Naturally, i think it's got something to do with about 40 years of soldering, but you'll pick it up very quickly. This is a perfect project for a practice soldering, because it's got big fat pads and it's also single sided, which means, if you screw up, you can remove components very easily. The only polarized components. Well, there's quite a lot polarized components.

Technically speaking, the diodes are polarized. They have to go in the right direction. The leds are polarized, they have to go in the right direction too. Otherwise they just won't light and the uh batteries kind of like it's important to put them in the right direction.

Otherwise, it will reverse charge them and they may be sad, and that leaves with just one led and the battery holders to go in. I shall crop these leaves down what big fat, pads, they're, great and also they're, well thermally, isolated, so they're quite easy to solder. Um, as opposed to some designs that use a a common ground plane and they put the leds and things on it and it sucks the heat away into the ground plane because there's a lot of copper. This is a color changing led for the power led.

It will slowly morph from red to green, to blue, to sound magenta, yellow and white and then back again and the reason i use it is because i can i could use an orange led or a green or a blue. It doesn't really matter. I thought color changing gives me all the colors, because i'm quite greedy that way right. Well, that's all the leds on now.

How is the time? Oh, this is pretty good. This is flying together. This is flying together at surprisingly high speed right battery holders. Now i've got a slight concern here.

A i should have just put a row of pads here because i could have made it fit double a's and aaa's. At the same time, it doesn't really matter, but these battery holders have a slight weakness. The little rivet that holds the spring onto the stem, which is separate, it also goes onto the plastic. So i'm going to have to be careful soldering them, because if you do solder it and it's too hot too long, it softens the plastic and it makes a bad connection.

This isn't good. It seems like a bad design. Also, these aren't particularly square, but you know they are what they are i'll use them. Maybe i'll just look for better connectors.

This is a prototype. The best way to test things is to make a prototype flow, some soda onto that, let it cool, and then i shall flow some soda on to other end. This is where the larger diameter soda would have been handier for depositing more solder in a shorter time, but it doesn't really matter. These are snip killers because they're quite strong steel, pins right next battery holder, i put the positive symbol and the negative symbol in the back.

I wish i'd put it in the front the screen print. This is why we make prototypes, because that would have been really obvious, that uh for putting the battery pack in again, it's a prototype. It's fine! Having said that, if it works well, it might not just be a prototype, it might be the finished design and if you need a specialist charger of your own, you know you might find it useful to uh just copy this, and do your own thing note that, Yes, it can charge unrechargeable alkaline cells, but they don't like it and once they're fully charged, because i built a version of this for that ages ago, that triple charged duracells and i was sitting at a computer - and i heard a loud in the background uh and I wonder what was that it sounded a pistol shop crack. It was one of the cells venting gas, because that's what alkaline cells do when you overcharge them.

When you try recharge them, they don't like being recharged even with the battery manager, ultra thing from innovations or whatever that company was i've, got one it uses, what's called cvsd. No, that doesn't that's completely wrong. That's conditionally verbal data modulation, it's nothing to do with pcr, which is what i was thinking of periodic current reversal. A technique used to get even galvanizing on steel where they apply the current to plate, and then they apply the reverse current to take a bit off, and then they put it back on again and it just keeps swapping the polarity um, with a bias towards the Charging current and it supposedly creates a better chemical deposition, creates better galvanizing and supposedly charges the alkaline batteries better, but um yeah they always end up leaking.

The holes are designed to take three millimeter spacers little pillars arm hardware. I suppose eight millimeter eighth inch should, i say, would work as well uh. This is a complete. Let's test this right, too art i'm gon na go.

I know, i'm not! I'm just gon na stick batteries in right. Now, i'm going to get a usb lead. Is this going to reach? I think it's going to reach. Let's just put it on like this, then it's almost reaching.

You know what i want. I want to measure the current one moment. Please usb power supply and monitor procured 4.98 volt, let's plug the micro usb lead in the power indicator led has littened, is now color changing how nice, let's stick in a kodak cell, which is a dollar store cell. This indicator is indicated.

What was the current before hold on? Let me get, let me see four milliamps right, roughly three or four milliamps for the power indicator. Uh, it's gone up to 30 milliamps for this. Let's uh stick a sony battery in let's stick an envelope in and each tab. I plug it in you'll, see this indicator charge and a nickel cadmium just for good measure.

There we go uh 100 milliamp, so that was about three or four milliamps before this will go down as they start taking a charge. The current will go down a bit but uh 99 milliamps uh, 99 minus. It started off around about, say: 3 milliamps, 96, divided by four equals about 24 milliamps, each, which is ample that's completely within the range of continuous trigger charging, which i'd say: 20 to 30. Uh milliamps so uh there it is.

There is the universal charger uh, which you can just leave these batteries in it the power consumption. Let me just work this out. For you, the power consumption is 5 volts. Uh equals iv times.

Um 100 milliamps 0.1 equals the power. Consumption is half a watt, which means that over the course of a year it's going to cost you 50 p to run 24 7. So really, you don't have to worry about leaving your batteries on charge continuously, and you can stack these. You can just put them end to end with those uh pads for spreading along, if you just make a frame that you put these screws through, it doesn't have to be like machine screws right that can just be ordering little wood screws into a piece of wood With spaces at the back, if you wish, but this system will gradually.

Oh it's just stopped. Charging uh, oh like that'll, be that connection then get a good decent, usb lead, but this system will just run off a standard, usb charger and it will just trickle these cells that what low capacity ones like these will be charged in, say well. That was about that was 25 milliamps. So that's 600 milliamp hour 600 divided by 25 milliamp equal.

It's gon na be about a day to charge that for these ones it could be two or three days, but it's one of these things that you just sit in the background, and if you don't you, if you don't need them instantly, then you can just leave Them just sitting there ready for use and they'll always remain fully topped up to full capacity. I would say: that's a good result.

18 thoughts on “Simple nimh battery charger with pcb files”
  1. Avataaar/Circle Created with python_avatars Hired Gun says:

    I am completely colour blind, I measure and mark band coded components myself , same when I have to do wiring on equipment at work , mark and lots of pics

  2. Avataaar/Circle Created with python_avatars geebsterswats says:

    When I heard you say "panty wings", mid-sip, I literally spit water all over the place lol

  3. Avataaar/Circle Created with python_avatars Gregory Thomas says:

    I found that I could recharge Duracell's two to three times before having issues with leaking…but now I just stick with Eneloop & Jugee.

  4. Avataaar/Circle Created with python_avatars deelkar says:

    I'm thinking Full Bridge Rectifier ™ -> LM317 or 7805 and power from any laptop charger, cheap car adapter in any polarity. With these currents the efficiency of the PSU is not really relevant, I guess

  5. Avataaar/Circle Created with python_avatars Ecospider5 says:

    I knew someone who was color blind that tried to get into the special forces. They said no because of distinguishing wire colors on bombs.

  6. Avataaar/Circle Created with python_avatars Namirred says:

    Searching for “axial lead bender” came up with the shaping tool. I have had one for a few years. They are also on thingiverse if you want to print them. Search for lead bender.

  7. Avataaar/Circle Created with python_avatars Hagen P says:

    "Color vision is not needed for electronics" — thanks, I agree and like that encouragement!

    (My color vision is fine, but it's really good to know I'm not the only one having trouble reading some of the metal film resistor values. And I always measure values, just to be sure.)

  8. Avataaar/Circle Created with python_avatars Philip Carpenter says:

    Looking forward to those files, Clive …. JLCPCB are going to have to do some overtime …

  9. Avataaar/Circle Created with python_avatars TinPlate Geek Too says:

    Clive totally missed the Watt reading on the USB monitor and just had to bring out the pink calculator. At least the calculator agreed with the monitor 😁

  10. Avataaar/Circle Created with python_avatars Myriad says:

    To be honest I was considering doing this anyway, probably much more crudely, but this makes me want to do it even more and with more polish!

  11. Avataaar/Circle Created with python_avatars iamdarkyoshi says:

    Also, I shimmed the tip on my iron using aluminium from a carbonated sugar syrup can, it improved the performance dramatically

  12. Avataaar/Circle Created with python_avatars Richard Turton says:

    Clive, if you had used 1.5 Hz (or 0.5 Hz) LEDs as charge indicators you could say that it was a charger with "Pulse Charge Technology".

  13. Avataaar/Circle Created with python_avatars Geoffrey Waldo says:

    I found a company that makes eyeglasses that have filters that help restore color perception for R/G color blindness, EnChroma. Was going to get a pair for my father in law who is R/G color blind. Didn’t want em. He’d worked on the railroad for decades and was used to things as they were. I could understand!

  14. Avataaar/Circle Created with python_avatars Paul Rowntree says:

    I was put off rechargeables years ago. Bout some very good quality batteries and a very good charger. After about a month, the charger just would charge two of them. If it had been a straight forward charger like this, I would almost certainly still be using them. Very nice Clive.

  15. Avataaar/Circle Created with python_avatars Mike Cowen says:

    That one-handed soldering method is exactly the same method I use. It does "just happen" somewhere along the line while accumulating forty-something years practice.

  16. Avataaar/Circle Created with python_avatars Geoffrey Waldo says:

    Just had a thought. Start trickle charging and the wine kit. Both would finish up around the same time, very convenient.

  17. Avataaar/Circle Created with python_avatars Geoffrey Waldo says:

    This is the charger I’ve been looking for! Cool design with the trickle charger. This is what you want…a charger that you can pop the cells into and have them ready for the weekend, no worries.

  18. Avataaar/Circle Created with python_avatars Damien Walsh says:

    Nice design. Just wondering why those boards look so light-coloured? Is there no soldermask on the top side? I’ve gotten green boards from JLC before and they’re usually much darker!

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