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A look inside a very common cordless ratchet as used in garages around the world.
Many of these unbranded tools are actually fairly well engineered due to their high volume of manufacture. This one has no fancy branding or features, but works fine. I'd guess it's probably used by many professional maintenance engineers in China as well as many home mechanics.
I've not used this tool in anger yet, so if you have experience of using one then leave a comment down below.
I must stress that ALL cordless ratchets are not intended for use with extreme force on seized nuts and bolts. They are more for whizzing them in and out, but can handle modest pressure on non-seized hardware. The weakest part on all these units is probably the pin that oscillates the ratchet mechanism.
I mentioned Tekamo HD, so here's a link to a video of Cam giving a genuine heavy user review of various tools:-
https://www.youtube.com/watch?v=4GwQ0iMR6Uk
The design of the tool and it's charger are very simple and functional. Just how tools should be.
The protection built into the battery pack makes it useful for other projects too.
I specifically avoid using intrusive mid-run video adverts, which means I don't earn as much from my content as other YouTubers.
If you enjoy these videos you can help support the channel with a dollar or two for coffee, cookies and random gadgets for disassembly at:-
https://www.patreon.com/bigclive
Patreon supporters get early access to videos as they are made, and also regular live streams.
This also keeps the channel independent of YouTube's advertising algorithms allowing it to be a bit more dangerous and naughty.
Other contribution options are available at:-
http://www.bigclive.com/coffee.htm
#electronicscreators
#Tekamo HD

It's a cordless ratchet as favored by mechanics the world over, but this one is a super cheap one from ebay and i got it really just to take apart and i get the feeling from the fact that it's got these label positions, but nothing in them that It is just a generic unit, so the idea of these is that you can put on a suitable, socket, here's a lovely purple one and it acts like a standard ratchet, including the little uh toggle at the back, that you can use to reverse direction, and you Can just use it to actually ratchet like this, but not on super stuck bolts uh. However, what makes this a bit special is that when you pull the trigger - and it's just a single speed, it's going to make make a bit of noise, it will rotate that and then - and this bit got me initially when you turn this round, it rotates in The opposite direction, uh, because i initially thought that these things had a gearbox and then some really strong cog wheel for converting to right angle drive. It turns out it's a lot simpler than that in reality. Oh look agrees everywhere.

That's fine! In reality! If you watch this ratchet mechanism now, if i actually click that round, you can actually see. Can you really see it moving, not really there's not a lot of visible movement, but this is the ratchet mechanism and the motor actually just makes that jiggle backwards and forwards, and in doing so it clocks it round step by step. It's a very odd system. I thought initially there might be impact just because of the noise.

It makes this loud rattling noise simply because it is suggesting forwards. Very clever, there's also a little white led here, so you can see what you're, triggering and also a battery level indicator here, which shows you. The state of charge left it'll be very simple. Let's pop the battery out, the battery is a 12 volt.

It most likely contains 18 650s i'll see how long this video is. If the video goes on super long, i'll, just put the battery and its charge in a separate video, but the main thing in this video is this one. It has another little thing: it's got an on off function that just locks the trigger and that's it. So, let's start taking it to bits, that's what we're here for i'll just start randomly taking screws out and see at what point it just disintegrates.

I suppose i should make a note of which screws go here just in case of different lengths, but hopefully they'll all be a similar size. Let's check that out similar size, similar size, probably the wrong screwdriver for this, but it's the one that came to hand similar size and finally get out similar size they're all the same size, a screw. I've also noticed a couple of metal tangs here, probably just the strength to stop the splitting apart and the batteries put in so to get them out, i'm going to have to leave them up. Maybe yes, they just pop up like that.

That's useful to know, and that just leaves these screws here. I believe these are a decent repetition. I guess ultimately, because china has lots of garbages and they're, not necessarily total status. Wars like like in other countries where they want the latest snap-on or milwaukee and stuff like that they're probably quite happy to use these, but i get the feeling that for super heavy duty um, you want probably to get a decent brand one with a warranty which Makes me think of cami at uh to camo hd, it's a youtube channel where kami is a mechanic, uh and brandon, and sean and others who go and fix heavy diesel stuff in canada? And it's interesting listening to cami talking about his tools because the way he says yeah i've warranted this one five times and it's like oh and it's prominent bran because he really hammers them.

Ultimately, i suppose the manufacturers rely on the fact that not many mechanics are going to really abuse the tools to death and i don't think cam is abusing them in the sense of just damaging them. I think it's just his work is very, very heavy. There's not much in it. There's a big motor there's a little circuit board down there, the heat staked in so it can't come out.

That's the leds not really bothered about that. A couple of wires going up to the led where's, the resistor. Oh that's! Coming off that little circuit board, so the resistor for the led up there is probably off this circuit board as well, and the little switch not really much to see here and the battery clips. Let's pop that out, okay, am i going to be able to get much further in here? I can see a pin that looks as if it's designed to lock things in i'm entering eve territory here, let's, let's use the incorrect tool to get this out.

A blunt pair of side cutters that worked is that a good thing to do yeah? Apparently it is oh there's a planetary gearbox, that's going to go together again. I think what we've got in there. We've got uh the bits the planetary gearbox was supposed to be going into right. I may have done the wrong thing, not to worry uh.

What about in here? I want in here to see how i can get this off, or is it just? Well? Maybe it comes out from inside oh right, so i'm just going to grab that with a pair of pliers and a hike it well. Another bits come out, uh quite oily, as you would expect and then there's a triangular drive. Let's hike the triangular drive. Oh there.

It is that's all we're looking for er, that's the little reciprocating pin. That is the very thing here that will snap off when you try using this with so much force to loosen a stuck bolt that it suddenly uh suddenly goes loose and it doesn't work anymore. That's the bed, so this, oh and then you can spill this round. I don't think you're supposed to swirl it around.

Oh and there's a little rocker in there uh just to actually allow for that movement. Can you see that i'm regretting not having paper towels now? Uh one moment please and i'm back, i took a an opportunity to go and see if i could find my circuit plans. No, i couldn't so. I tried using an appropriate tool.

I could not get that circle about it's one of those jesus clips that you shout jesus when it pings across the room and it would never be found again. So it's maybe a good thing. It's probably also full of springs, but there is a little pivoty thing that i was talking about now. You can see it that that pin goes into and as it rotates it.

Basically, it rotates and it pushes this ratchet backwards and forwards. Mm-Hmm jolly good so uh that didn't take too long uh. So, let's take a look at the battery, then so summary fairly powerful motor single stage planetary, gearbox driving onto this rotating pin that then jiggles the ratchet that's popping out uh backwards and forwards to clock it round very simple, very straightforward! It's much simpler as expecting right! Tell you what i'm going to clean all this up and then we'll explore the battery one moment please: okay, next part of the teardown, the battery pack. Incidentally, i got this all back together.

It worked fine, but then i suddenly thought what, if i could actually change that, pin what if the pin that is likely to shear in there is swappable, so i took it all apart again: uh, it is not swappable, that's a shame. Maybe the whole insert is i'm not really sure. Anyway, let's take a look at the battery, which is most likely three 18650s. It has a little charge port on the side and the charger you get is a little plug-in charger that plugs straight in the battery.

I suppose that makes sense. This thing looks as though it's clipped together, let's use force the force and try not to burst any lithium batteries. It's not going to make it open. Well, that's a clip.

I'm going to shine a light down here and see. Is there any other clip? Okay right, i think i may have to un clip something down there, i'll just pry it randomly. What's the worst could happen, oh no! That could break that. If i'd do that, uh, let's just write too, i may have to pause.

This is not coming out. Maybe there's a clip down there hold on i'll, just shove, the screwdriver up here. What's the worst could happen, i could burst the battery pack, it would still work. That's changing shape the battery pack, i'm not sure the battery pack is supposed to change shape right.

One moment please see i gave up too soon the sides the other clips are under here. So there's two clips under here that you just have to get down and carefully pry them out it's in this springy plastic that actually clicks it in and then other clippers at the back. There are our three 18650s, not much circuitry, not much circuitry at all, and it looks like it's uh, a all the circuitry on one side right, tell you what tell you what i'll take a picture of this and we can explore it, not that there's much to Explore, but i shall do that one moment please and resume. Okay, it's a very straightforward thing: it's got a chip dedicated to protecting three cells.

The chips number is csc5113a, not much information about that online, but it turns out. I had this little module from ebay and it is almost identical as a slight component variation, but it is more or less the same circuitry and the chip number on this one was cm1033 and there is a data sheet for that. So we can take a look at the circuitry, so things worth looking at here. The batteries are connected with uh.

The tabs coming here, plus there's also a connection there and a connection going to the bottom of the battery stack here. So it basically has connections all the way along the battery, so it can monitor the voltage there's a bit of filtering circuitry here, 1k resistors and capacitors, so it can basically look at the voltage across the cells and see if any one of them has gone over Voltage or reached 4.2 volts or been over discharged below about 3 volts, and if it does, it will turn off one of these mosfets, this little a2shb, small, mosfet and sears. The diode is from the auxiliary charge contact here because you can charge this by plugging it into a charging base. But it also has this charging socket built in with the positive pin connected straight to the positive, which is the other connection for the charge port and the negative here is connected over to this metal plate, and it goes out via this diode.

That's why the diode is pointing with the band towards the negative and this transistor here this little mosfet. It doesn't have to deal with much current, just the charging current so somewhere between 500 milliamps to an amp uh. So that's the one. That's been used to turn off the charging current once the voltage on that any of these cells reaches 4.2 volts.

This is the one that's switching the current to the loads um and there is supposed to be a protection diode across here. There is on this other one, it's basically connected across the power tool terminals and what that means. Without this diode it means if you're pulling the trigger and the battery runs low and it suddenly cuts out when this mosfet turns off. Theoretically, you could get a back emf spike from the motor in the tool and it could actually damage the mosfet.

It's a bit of a strange thing to leave that out. Other things worthy of note, the other components here are for monitoring when it is charging in the first place and also for detecting over current by measuring uh the voltage drop across the mosfet. The mosfet is a k391 which is rated 25 volts 48 amps and has a very low on state resistance of 7.5 milliohms, which is ridiculous. Anything else worth looking at here, not really, let's take a look at the schematic, so here's the schematic, here's the charging connection here and the only real difference i can draw in here should i say, is the other way around.

Let's draw it the correct way around i'll make an extra big fat diode, then there's a diode there, just to possibly protect against self-discharge through the charging socket is in fact, because i know exactly what's in these crappy chargers. It's the most basic thing possible is basically a little switch mode, 12 volt plus supply with a resistance series and then really rudimentary circuit to measure the voltage across the resistor. To tell how much current's flowing through this resistor here is used to detect um. When there's an over current situation, because when it's charging it detects via this resistor, the the charge is being applied to it and it'll turn on the suitable mosfet here.

But when it's discharging it turns on this mosfet and uh centers the voltage across at that resistor. If it gets too high, it knows that the current flowing through it is huge, and it will actually turn the mosfet off to protect the circuitry. That could also uh result in that sort of collapsing field thing that little diode would have been quite handy across that um. There's the three cells with each has its own one k, resistor three times one k, and if this is following the standard format, i'll guess that those are probably 100 nano.

Three times 100 nano they're just there to provide basic filtering. So it gets a nice stable. Uh voltage reference what else resistor? I haven't really a clue what that's for? I don't know if it's a part of the over discharge protection circuitry, i'm not not sure, but it is textbook. It's basically following this schematic on the pcb.

Now here's something worth mentioning. Oh, this is worth mentioning i'll draw on this because i noticed when i was measuring the voltages across these hold on i'm going to measure them again and i'm going to write them down one moment: please: okay, i've measured the cells; incidentally, the construction of these, the Cells are all connected in series without this red one actually carrying a lot. The current um but they're connected in series, but at each connection point between a cell. There is that tap off point, so it can monitor the voltage it's kind of essential in lithium cells and, ideally because there's no balancing in this circuit, the voltages across each cell should be the same.

In this case. Cell 1 is 3.69 volts. Cell 2 is 3.75 and cell 3 is 3.75 and that slight voltage difference. It's not too bad.

But if you have a significant voltage difference between the cells, it severely impacts the charging ability or dischargeability of the pack, because this thing is looking for the first one of these to reach 4.2 volt. So supposing this is charged up and this one is lagging behind by say about say, 0.06 volts um, then, when one of these cells is going to be the first to reach 4.2 volts and it will cut off the charge, while this one isn't quite fully up To charge, and likewise when you discharge it the first one that's going because it didn't get a full charge. The first one that's going to be discharged down to about three volts, and this, where this will cut off, is going to be this one, so that one cell out of sync, with others, can actually have a significant effect in the cell capacity and i've seen a Situation where people have let batteries they've stored them in a bucket water has leaked through the roof, and it's immersed the battery, which isn't a great thing, the first place, but it's just at one edge of the battery and the pack has survived, but its capacity has Gone down because one of the batteries has discharged through the salty dirty water in the bucket, and it just knocks him out of sync. If you opened that battery and it was actually in a clean condition inside not too corroded um, keep in mind that faulty circuitry will uh could potentially result in overcharge of a lithium cell and a little incident.

But if one of them has gone seriously out of a balance with others by charging that one back up or discharge the other ones down to that same level to match all the voltages will often sort of restore the capacity of the pack. But it's also uh one cell repeatedly dropping voltage as a sign of either faulty circuitry or a damaged cell, and that is a kind of case of the thing to do then is discharge that pack completely and then dispose of it in a recycling system. But there we go quite interesting, nice construction, i mean it seems nice construction, certainly i'm guessing a lot of these are used in chinese garages and certainly a lot of diy or seem to be very happy with them, because they're not really hammering them in the same Way that a mechanic would but there we go interesting now i shall put it back together and i shall have uh well cordless ratchet for when i actually end up needing one but quite neat much simpler than i was expecting just really simple. Just that single stage.

Gearbox and the uh, the vibrating ratchet mechanism and the battery is also just cut down to the bare minimum, but still absolutely functional. Oh, these are labeled inr, 18650, 1500 milliamp hour. In a way, these little batteries, which are very similar to the ones sold by aldi and lidl for their 12 volt tools in a way these are actually quite useful in their own right as 12 volt, lithium batteries, so all good stuff, all very interesting.

14 thoughts on “Inside a cheap chinese cordless ratchet”
  1. Avataaar/Circle Created with python_avatars MillenniumTech says:

    This type of battery design without balancing is exactly why laptop batteries do not last at all, especially ones from the early 2000s or the very latest ones (the ones from the mid 2010s are still good, I have a 5 year old second hand laptop with a functional original battery that has worn a bit but is evidently far more durable than say the crap that Dell has been using the past few years that you are lucky if it lasts 2 years as I have witnessed with other laptops I've had or currently have).

  2. Avataaar/Circle Created with python_avatars 2011joser says:

    The rotating pin is not likely to break first. At most, it will be rotated minimally until the pawl in the head engages with the teeth of the square drive. In these cheap ratchets, the failure point when using a lot of force to break a fastener loose is the plastic body.

  3. Avataaar/Circle Created with python_avatars Trond Børge Krokli says:

    Thank you for this video, it really reminded me of Rainman Ray's videos, both because he uses several different cordless ratchets and because he has also told his viewers about the "Jesus clip", which gave me a chuckle, especially when you reminded me about the reason for its nickname. 😁😁

  4. Avataaar/Circle Created with python_avatars John Crooks says:

    A useful tool to have, but will it have enough torque for the average job. You didn't seem to mention the power of the chunky motor which would have been good to know too.

  5. Avataaar/Circle Created with python_avatars mueffe says:

    My sister had a cordless grass cutter with the same exact 12v battery. She send it to me to look at it, why it didn't turned on. I've check the motor, switch and wiring. Nothing out of the ordinary until I got to the battery. At first it looked OK. After close inspection, the black shiny body actually hides the semi melted body. The circuit didn't protect the battery from melting the plastic. Luckily it was not a fiery explosion.

  6. Avataaar/Circle Created with python_avatars Malcolm Stockbridge says:

    I bought one for my Grandson for his birthday…he is more than happy going around pretending to be part of the red Bull F1 team.

  7. Avataaar/Circle Created with python_avatars Sewan & Sawen Creations says:

    Can you make us a schematic for nancys brain? Many are seriously wondering how that ball of wires even turns the lights on in the morning.

  8. Avataaar/Circle Created with python_avatars mweverett says:

    This triangular back config is used by everyone for 3S 18650 packs. I think I first saw this in a Rockwell driver. Rebuilding these is doable but a bit advanced.

  9. Avataaar/Circle Created with python_avatars Ray Mitchell says:

    Cordless racket ? Racket in this case means both: (Confused Clattering Noise) AND (a business making money using dubious business practices) Why these cheap death-wish things don't explode more than they do amazes me! You probably should wear gloves you don't know what toxic shmoo they used to lubricate that… Racket! LOL

  10. Avataaar/Circle Created with python_avatars Trashkov says:

    I was incredibly surprised the first time I saw a large lithium pack that got charged by a "wall wart" with a barrel connector.
    I'm so used to seeing a massive hunk of ABS plastic that the idea never even crossed my mind that the battery could be charged from a simple power brick.

  11. Avataaar/Circle Created with python_avatars mweverett says:

    The higher end Harbor Freight cordless tools are nice stuff these days, likely made in the same factory as the big name tools, with the same materials. Originally these were air driven. Never use these with the force you would a normal ratchets.

  12. Avataaar/Circle Created with python_avatars barry fuller says:

    Funny thing is I just pulled my one of these our of storage with 2 batteries went to charge it one charged no problem the other battery flashed on off ( red/green) so I took apart this afternoon thinking one of the batteries gone

  13. Avataaar/Circle Created with python_avatars Conor Noakes says:

    I’ve often wondered how compatible these are to the Lidl X12V system of tools & batteries

    They’re made in a very similar fashion to the older 12v battery “Dremel” tools they used to sell prior to going ‘internal battery + USB-C’

  14. Avataaar/Circle Created with python_avatars Wicks says:

    I have been using one of these for the last ten months and so far its holding up okay. For a bit of context my main work is small engine repair so no doubt it gets an easy life, I'm sure if I gave it to one of the commercial boys it would die in short order.

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