eBay trash USB charger 2023 - with schematic

Much better than the last similar looking unit, and this one is easily hackable to your chosen current by swapping resistors. In this video I did a simple hack for a 24/7 trickle charge.
This unit is worth buying just for the case alone for your own custom charger project.

I get the feeling this is another clone of a clone - where a circuit has been modified without fully understanding the purpose of some of the components. In the case of the strange pair of differently sized parallel resistors, I think it may be based loosely on the previous unit which had a similar arrangement.

As supplied, the unit works as a very simple charger, but the current is high enough to require that you remember to take the cells out of it after a suitable length of charging time. It's too easy to forget that cells are charging and a prolonged period of high current overcharging can be detrimental to cell lifespan.

NiMH (Nickel Metal Hydride) and NiCd (Nickel Cadmium) cells are not like lithium cells, where there is a very decisive end of charge state (usually 4.2V). Instead the smart chargers have to detect a slight change in voltage when a cell is fully charged and bubbles start to form on its electrodes, or they may detect a rise in temperature or stationary voltage. When a NiMH or NiCd cell is fully charged it has a chemical reaction internally that converts the gas bubbles back into liquid, and during this there is heat generated and higher internal pressure.

For fixed current charging at higher currents you do have to avoid overcharging as the chemical reaction that recombines gas to liquid is only capable of handling a low level of charge current.
At very low trickle charge currents, the cells can be left charging continually without affecting their lifespan too much. However, the trade-off is the time taken to charge the cells. Not an issue if they're just being topped up or being kept on standby.

The other advantage of a simple charger like this is that it will handle older cells or ones that have been accidentally over-discharged, where a smart charger will either not recognise their presence, misinterpret them as being non rechargeables and reject them, or terminate the charge far too early.
In the case of accidental over-discharging, a seemingly dead cell can be brought back gently in this type of charger before being charged quickly in a smart charger.
Because the charger doesn't do any tests it will also work with difficult cells like the low capacity ones used in solar lights.

Aside from the hack/mod that I show in the video, you could also just fine tune the current by swapping the 18 ohm resistors for a higher value.

This also keeps the channel independent of YouTube's algorithm quirks, allowing it to be a bit more dangerous and naughty.

#ElectronicsCreators

[stepheneyles]

I can see Clive making a video in 5 years which shows that they've watched this and changed their design accordingly!

[UpLateGeek]

I dreaded working with SMD components for a long time. Partly because they're so tiny and my hands are a bit shaky, but also because it meant I'd have to buy a whole lot more components. But then I saw a few projects on the Interwebs that I wanted to build, but they were all SMD. So I bit the bullet and ordered the boards and parts, and gave it a go.

To my surprise, it wasn't nearly as difficult as I thought. It didn't take long to get used to the tiny components, even with my unsteady hands. I even built one of Rasteri's weeCee tiny PCs, which required aligning 1.25mm twin row SMD headers within a fraction of a mm on four sides to fit the processor module.

Now I've designed my own projects that use SMD parts, designed the boards got them manufactured and everything. I've even printed and etched my own home made boards using the toner transfer method. Basically the only reason I'd go for through hole over SMD is if I wanted to use a specific through hole part (potentiometer, header pins, specific IC that I already had in through hole version), or if I wanted the circuit to look vintage (I'm currently designing a clock that uses a vintage VFD display, housed in a wood and acrylic case that shows off both the VFD and the PCB).

[KrisisVal]

you don't have to replace the 5.1 ohms with a diode if you cut out the 18 ohm resistors, because the reverse breakdown of the LED's will be higher than the battery voltage so the LED's will block current from flowing back into the charger and discharging the cells.

[TopEndSpoonie]

Hahaha. Take out 6 components, add 1 and make the whole thing better. Great work.

[GizmosWorkshop]

I was taught electronics when I educated as a Radio TV Repair tech in the late 90s, and SMD was just a side notice.. Got my certificate and there was no work so I went into telecoms instead.
Been there in various jobs since then, until recently when I started working in an electronics factory and Oh sweet lord this stuff is tiny.. My glasses need glasses for some of the stuff :D

What I learned pretty early though, is get yourself a syringe of flux paste, and just jab that on there before you solder the component down, and also a sharper tip helps. The flux will really help spreading the heat, and the sharp tip will make it less messy.

[cameradoctor]

When digital point and shoot cameras used AA batteries, customers were often impatient and wanted their batteries to charge fast !! ... there were a lot of 'Fast Chargers' sold, and I am sure they Nuked the poor NiMH cells ... I tried to sell a slower charger and a spare set of cells, but not everybody could be taught ;)

[Alloverthecarpet]

Your NiMh trickle charger was one of the first projects I did getting back into electronics this last year. I use portable radios pretty heavily in my day to day and having a set of batteries ready to go at all times is really convenient. Thanks for doing what you do!

[RJHElias]

That solering tip looks like a elephant foot for smd soldering. Never the less, you do a great job Clive. I am a fan forever!

[johnbrandolini]

I'm glad you brought up the point that the modified charger was intended to "top off" charged batteries. Basically the idea is to provide just enough current to overcome the cells internal resistance. That's actually called maintenance charging. I designed a 12.6v gel cell charger based on a 7815 series regulator that provides it's output based on the state of the battery. The charging current will be 1 amp when the battery is discharged and will taper off to about 8 ma at full charge. I chose the 8 ma value based on the data sheet for the battery. The charger and battery are in an emergency lighting system I built almost 10 years ago. The battery has lived well beyond it's natural life thanks to maintenance charging.

With regards to surface mount components, I would recommend getting a microscope to assist in placement especially for the 0805 and 0603 parts. I have a Mustool microscope that has it's own display and can magnify up to 600x. It wasn't that expensive- under $50 USD (41 GBP) on Amazon. As a radio amateur I receive the ARRL's QST magazine and a couple of years back they ran an article about using a PC cam as an alternate to a microscope. I tried it and it's doable but it is cumbersome and the magnification is limited. Solder paste is a much better alternative to fluxed solid solder as a dab will hold the part in place until you put pressure on it with tweezers. Also you get better control of the amount of solder on the pad. As to the type of tweezers the ceramic tipped ones are ok for passive components but not so good for actives such as MMICs where they might be subject to static damage. For that reason I have a grounded mat on my bench and use conductive tweezers when I'm working with actives. My workspace is a scaled down version of what I used to use back before I retired.

Finally, a schottky diode would have been my first choice since it has a forward voltage drop of about .1v as opposed to .6v for a standard PN junction diode. At 40ma the diode will dissipate only about 4mw. Later.

[maltoNitho]

What a lovely follow up! Just last weekend I was thinking about building your previous trickle charger… but instead I just ordered one of these and will just remove the resistor. Thanks as always for the entertaining and educational watch!

[daveedee]

I've been waiting for this video since I bought a bunch of these dirt cheap chargers sometime last year. Thanks Clive.

[grantrennie]

Thank you for another great video Clive, have a nice day and be well everyone

[Niei]

That beefy charge lead probably contains at least 4 strands of wire 😂

[coverfrequency]

I really enjoy these cheap electronics teardowns. I've integrated cheap circuits into prototypes.

[beefaroni]

all these weirdos telling me i need tweezers and a magnifying lens and a tiny soldering tip meanwhile you're out here rawdogging it with a standard tip and just wiping them off. well, guess i learned something today.

[panthony]

Would very much like to see you do a dedicated video on how to reverse engineer a circuit board, from analysing the board to producing a schematic diagram.

[elk]

im so glad im ultra near sighted. ive never needed a magnify glass since my eyes have a focal distance of 1.5 inches. in electronics class i was the only one able to do smd chips and ics without a microscope. so the teachers had to debate how to grade me since i had a advantage over all the other students.

[chaos.corner]

It could also be turned into a handy power supply if you were looking for easy battery swaps.

[zomgsako]

Back in the days then I was young and naive I "hacked" one of those spring loaded chargers, basically threw out all the circuitry and just added a connector to hook it to a RC battery charger. I needed to charge 4 eneloop at a time (for Tamiya mini4wd models). Turns out the springs can't bear a 2A charge, they get super hot and melt. Lesson learned!

[Richardincancale]

6:28 If you snipped out the 20 ohm resistors the LEDs would act as diodes and stop the discharge anyway wouldn’t they?