Inside an Aldi Ferrex 20/40V battery (with schematic)

This was one of those reverse engineering projects that had to be revisited a few times. The circuitry is unusual and it took a while before the puzzle clicked into place. It's always that bit harder to probe surface mount components on a double sided PCB if trying to probe both sides at once.
That said, the whole design can be summarised as follows. It has two independent batteries that each has its own charge monitoring processor. One processor is the master and deals with pack status communication, while also communicating with the other battery's processor via a bidirectional opto-isolated data link.
The method of detecting individual cell status by gating a voltage divider feeding an analogue to digital convertor (ADC) is weird due to the odd resistor values for each cell. My best guess is that the design is trying to fit to nice round figures in the software.
The NTC temperature pin can have either of the battery thermistors connected to it, plus potentially do simple bidirectional communication with the tool or charger.
The two rows of pads are probably for testing and maybe programming of the packs during manufacture. It would make sense to have the reset circuit in their vicinity.
Update. I couldn't quite work out the weird communication circuitry on the NTC/T pin. It turns out that it was different to my schematic, and the two 750K resistors are a divider driving the gate of a MOSFET that is switched by an external 12V communication signal, and then converts it to a logic level signal for the processor. The thermistor pin receives data and the ID pin sends it by switching an external 12V signal to 0V.
If you enjoy these videos you can help support the channel with a dollar for coffee, cookies and random gadgets for disassembly at:- www.bigclive.com/coffee.htm
This also keeps the channel independent of KZbin's algorithm quirks, allowing it to be a bit more dangerous and naughty.
#ElectronicsCreators

[@dcallan812]

When you look at the board and software it's amazing, they can get something this clever for the price. When you think back just 10 - 15 years. Very interesting video 2x👍

[@ChoppingtonOtter]

Makes you wonder what we will have in another 10-15 years!

[@dcallan812]

@@Okurka. I click the 👍 button once but if I appreciate the video I like to say 2x👍 up in the comments. Have a Merry Christmas and Happy New Year 2x👍

[@dcallan812]

@@ChoppingtonOtter Yes and everything is getting smaller too. (well not my waist 🤣) Merry Christmas 🎅🎅

[@dcallan812]

@@Okurka. Im not?? I like using the thumbs up button AND I add 2x thumbs up because I really lime the video

[@dcallan812]

@candyman I thought he was a bit simple, not quite retarded but still.

[@vatterger]

As a young electronic engineer: Really love your reverse engineering videos! You've explained/shown so so many creative and low cost circuit designs over the years, it's really educational! Thanks for that!

[@whatilearnttoday5295]

Better than the tradition of forums where everyone new is screamed at about how dumb they are.

[@tniemi]

Totally agree. I really like that someone opens up these circuits so that even an amateur like me can see how things in the modern life work. Information on this level is unfortunately rare. Thank you Clive for NOT simplifying things for us! (Also my wife falls into a blissful sleep when I watch your videos at the evening. :D Good stuff.)

[@TopEndSpoonie]

Wow, so much involved in that one. Thank you for your efforts 👍

[@chrislloyd9619]

Your video saved two of my batteries . I let them go flat in the garage and the button showed 2 lights and would not charge. After watching your video i jumped the second side off a good battery b2 +and the b2- and after half an hour it charged a treat on the charger. Now i have 4 good batteries. Thanks for the in-depth review and saving my batteries.

[@bigclivedotcom]

If a battery has dropped in voltage too low it's better to gently bring them back with a low trickle current.

[@andytaylor8802]

I have a battery pack that is fully charged but won't allow a power tool to run. Is it totally different now or could it be fixed? Problem we have now is that these batteries are as hard to get as rocking horse manure. I don't suppose you know if replacement boards are being sold anywhere?

[@jasonkmec1589]

The microcontrollers look to be from Fremont Micro Devices, from their line of very cheap 8 bit PIC clones. Looking at the datasheet for the FT64F0A5 for instance, shows a matching pinout to the power, gnd, and reset signals from the schematic. Many of the parts from this product family also have a 10 or 12 bit ADC.

[@williamromine5715]

Those of you who have been around for a while, know that I know nothing about he is talking about, but this one might have been in Greek and I wouldn't have been any more lost. On the other hand, I enjoyed the video as always. His voice is so calming, that the stress of the day goes away. This is the only website that I am subscribed to that I don't understand a word that he says, but that I open as soon as I see a new episode available. Merry Christmas to all, and to all, goodnight.

[@Derek_Garnham]

Don't be too surprised if something starts to make sense, you may be learning subconsciously.

[@rogerhargreaves2272]

Your honest. I’ve learned a lot from Clives channel. Happy Christmas anyway. 😊

[@williamromine5715]

@@Derek_Garnham Possible, but at the age of 80, it's not important that I understand what he is saying. His knowledge of his subject comes thru, and I am always attracted to a person who has knowledge and enjoys passing that knowledge to others. In addition, his subscribers are courteous with each other, something not common on other websites.

[@Derek_Garnham]

@@williamromine5715 Quite so, particularly what you say about the subscribers. All I'm saying is be ready for the day you wake up to the odour of solder flux and find out that you've converted your alarm clock in your sleep to run on vape batteries (charged from a pound-shop solar garden light).

[@williamromine5715]

@@Derek_Garnham That would be neat , although I'm not sure I know what you said. Thanks for the encouragement.

[@amorphuc]

Good Grief! & WOW! I'm blown away by your reverse engineering of this thing. Very complicated and couldn't help but think of the corresponding charger that talks to it. I think you mentioned the deal you got this at and it seems like you scored! I mean, the battery alone right? Way over my head but I think I learn a little something each time. Thanks!

[@jkobain]

Well, I didn't hope to behold the times when microcomputers are cheap as dirt and exist in multitude in EVERYTHING. I can't express how I was amazed when I discovered they made a specialized chip to replace a huge mess of discrete components with a single dedicated unit. So much efforts went into engineering this, simple from the outside, thing; so much efforts you put in reverse-engineering them. That's a lot, thank you very much!

[@nec3f]

In an entirely unrelated example I can think of, two thermistors are placed next to each other for redundancy. That way, even if they're both reading 'normal' temperatures, the controller knows there's a problem if they drift too far apart. People have problems with false positives when they don't read the instructions and place them away from each other thinking they'll get better coverage.

[@matthewbaker6827]

Or perhaps, and I'm a mechanical engineer so please be kind, the schematic called for two thermistors i.e. one per battery but the intent got lost when the job was thrown over the office cubicle wall and the layout and mechanical engineers made an assumption. However, I think that the your rational is more likely, mine being the flip side of yours:-) PS edited for typographical error.

[@andymouse]

Makes sense.

[@Eddiecurrent2000]

I thought the same, the thermistors are probably important to stop runaway and not just charging temps, so having two would mean the uC definitely has the correct temps.

[@devttyUSB0]

Awesome reverse engineering. That circuitry is amazingly complicated. Does look like you're getting bang for your buck though. :)

[@Derek_Garnham]

Sherlock Holmes would have been proud with your recovery of the chip ID. Nice forensic technique.

[@sundog486]

Things just get more and more complex as we try to get more and more out of less. Well done on this one!

[@BTW...]

Despite the dual battery (and so, voltage) circuit, this appears to be A LOT simpler than what's inside the dreaded Milwaukee M18 battery packs. The same in depth circuit analysis (for Milwaukee M18) would be a significant benefit for the users of those tools who suffer the mystery of those 'battery management' boards and big $$$ cost of replacements.

[@Rx7man]

Yeah, same with Makitas!

[@manuelhung7571]

Milwaukee tools are becoming less reliable with each iteration of the range. The hype was big at 1st here in the UK, but inevitably in the name of even bigger profits, standards suffer and Milwaukee seem to be cashing in with a very short-term view. There is a channel - Dean Doherty here on KZbin, a guy who repairs powertools as his business. He points out regularly the failings of Milwaukee and falling reliability standards. A very interesting channel with honest opinions. Makita still make the best grinders, Hikoki (formerly Hitachi) the best Nailguns along with Paslode, Bosch the best Concrete Breakers, etc. Not always best to have brand loyalty with powertools even though it is financially beneficial to have one battery eco-sysyem. That is how they hook us in with Bare Tools being far cheaper when you already have the batteries/charger, often the most expensive parts. When you add the interlocking case systems like T-Stak II for instance, they sort of have us by the b0llocks. The EU if they want to do something useful, would standardise Batteries, Chargers, Cases, etc. They are attempting this with phone chargers insisting that any new phones sold within the EU henceforth will have to be the Type C charging interface. Something which Apple are not very happy about 😂.

[@mevk1]

My 10 year old, ten cell 18V weedwacker stopped working so I desoldered the beast and found 3 corroded cells. Rather than tossing the whole thing,I turned it into a 5 cell pack and pieced it back together. Amazingly the battery still has 70% capacity but with half the cells, theoretically last half the time. The electronics still kinda work but the cut-off voltage strangely went from presumed 2.5V to measured 3.5V so time between charges is greatly reduced. OK though since a full charge is still enough wacking for my yard. BTW, the number of SMD components on these double sided boards is mind blowing and alien to me - you deserve at least two pints after reverse engineering -cheers!

[@manuelhung7571]

I just recently bought the Ferrex 20v Combi Drill/Driver/Hammer (WWS-ASBS20-SP for £18 Bare Unit. Unbeatable value for money, solid construction and takes this Active Energy 20/40v battery. If it lasts me only 6 months then it has earned its keep but it has a 3 year warranty so.... absolute bonus. Don't know how they manufacture these units for the cost, crazy. I couldn't buy just the motor for much less than the price of the whole unit. Having mostly DeWalt and Makita (refuse to jump on the Milwaukee hype train), just had to get one of these for the fun of trying out the quality available at this price. Plus, if anyone needs to borrow a drill, I needn't panic about my Makita/DeWalt XRP being abused by a novice family member, I just lend them this 😊 Ferrex. Always found it incredibly annoying when family/friends expect to borrow a professional, expensive tool and inevitably abuse it because they didn't pay for it, only to return it covered in crap, bashed up and wobbly bearings that were fine when they took it. Lent out an 8 month old DeWalt Cross Pull Mitre Saw some time back to an idiot neighbour who put down some Laminate Flooring, only to get it back with the noisiest bearing I have ever heard. How you damage a main bearing on a large mitre saw cutting just thin laminate flooring is beyond me. You expect lost Carbide teeth on the blades where they stupidly cut something with nails in, but a whole bearing wrecked 😮. Cost me £80 in repairs for a fool to floor his downstairs. As for warranty - DeWalt would not have believed the bearing on the main drive shaft had failed just 8 to 9 months in due to proper usage. A 180lb Gorilla swinging on the handle maybe, a routine failure, absolutely not. I also bought the Ferrex 18v nailer which this far in, 4 to 5 months, is very good, no nail jams, smooth operation and effortless power as a 2nd fix nailer shooting brads upto 50mm into hardwood, softwood and even plastered walls for fixing architrave, dado rails etc. Always used a gas, then pneumatic nailer before this. The Paslode is great, as is my air nailer hooked to the compressor but the Ferrex works just as well for anything upto 2" brads, anything longer, I use the Paslode. I always swerved Aldi's WorkZone products because they were crap, similar to B&Q's Performance Pro range which were also complete crap but Ferrex in comparison seem really good value for money. Tempted to buy some Ferrex Pro tools, maybe the Brushless Impact Driver if I can find one. They appear to have an all metal gearbox housing as well as a fully metal gearbox. The Parkside Pro range looks to be well constructed too. Never been a better time for buying powertools at the cheaper end of the market to see how much value for money you can squeeze out of them and also to test how much better the high-end tools we pay a fortune for actually are or are not. Keeps the big manufacturers on their toes 😂 which is never a bad thing.

[@lint2023]

Hey. Merry Christmas and Happy New Year! Thanks for another year and all the good cheer.

[@ALAPINO]

I live in Canada, and I am always surprise how much Aldi house brands make it over here. Ferrex tools that have made it over have been fantastic and were cheap as chips. Particularly the bit sets, excellent value.

[@Wpjgdmtu]

Thanks Clive, was looking forward to the battery breakdown! Cheers

[@strongandco]

congratulations on the reverse engineering, that's impressive!! Also Happy Christmas Clive 🎉🎄🥳

[@youdontknowme5969]

Happy Winter Solstice ❄🌌🌙🕯

[@iaov]

I really enjoy these videos and your excellent explanations. Thanks!

[@ThriftyToolShed]

Great video Big Clive. I did not know that Ferrex had the dual voltage packs. I have an older video looking inside the DeWalt FlexVolt and I was amazed and a little bit scared of how complicated the switching contacts were on it to put the 3 sets in either series or parallel. I did not see a microprocessor on the board for it. DeWalt usually don't have one. Unfortunately the whole board is covered in thick coating making troubleshooting difficult. Thanks for the look and Merry Christmas!

[@nialldaly7108]

Excellent teardown and Rev Engeneering not only of the circut but the rational behind it. Thanks Clive, keep up the good work. Would be interesting to do a comparrison between the Aldi Ferrex and its compatriot the Lidl Parkside. Amazing how on the surface all these look the same, Riobi, Ferrex, Parkside Black and Decker and none fit each other, I know there are adaptors., buy not redaily available in a pinch. Another interesting fact to know is how the cells in these batterys compare, ie no of mA they are and rated and actually good for. Some of the cheaper chneese 2200mA dont even come close to stated ratings. Hence why people buy Riobi used battery packs to build their own Powerwall.

[@keithking1985]

Thanks Clive, merry Xmas 🎄

[@3niknicholson]

01:25 ..and for those of you with low patience...made me chuckle.. how did you know i was watching..I am a tech, and really appreciate your Scots intelligence, clarity and style, sir.

[@EMS.Fire.Welder]

Thanks so much for your videos! It helps me get a better understanding than just school theory

[@shaunmorrissey7313]

Excellent, these batteries fascinate me, that's not how i thought it was going to work, it is a tad more complicated.

[@mattmoreira210]

Wow! How convoluted of a design. Loved it! 😂

[@leotoro51]

Thank You mate :) Have a nice day !

[@andrewwmacfadyen6958]

I use various power hungry cordless from different brands including Mac Tools, Macalister, DeWalt and Keilder but I have been seriously impressed by Ferrex 20/40v tools. The 20/40v batteries give seriously impressive performance in my chain saw as a result I have bought other Ferrex tools.

[@paulharvey1624]

Thanks for this amazing video! I can confirm that having tried to revive a battery with a trickle charge and failed . Tried the force reset and boom 💥 it’s now charging!

[@daveroche6522]

Thank you and Happy Christmas Big C (plus Ralphie & the Max Beard Club [mine grows white with flecks of dark brown/black for some reason - very timely!]).

[@bigclivedotcom]

A salt and pepper beard?

[@wegmandan]

Merry Christmas Clive

[@PhilippaGordon-z2b]

Thanks for this really helpful breakdown. I had a battery that just flashed red on the charger. Using your info I tried shorting the reset caps but noticed one didn't have +5V across it. There looked like an OC between B1+ through to the next door B1+ shorted with a link and now fixed.

[@enoz.j3506]

Interesting Clive,the talking to both MCU,s via optos could have a benefit of allowing lock up to be monitored,1 checks the other etc.Most if not all MCU's have the brownout ability,the strange divider battery monitoring might be so the A/D converter (8 or pos 10 bit) is working at max resolution,i had a similar problem on my 8 channel designe.Good and detailed job you did there. Thank you.

[@RobWVideo]

It's interesting that Aldi sell Ferrex tools in Australia as well, but with what appears to be an incompatible "Xfinity Plus" 20V battery standard. The pins are in different locations and the actual physical shape of the slide-in battery connector is different. I guess there might be a patent issue or maybe it's just to stop parallel import of cheaper equipment from overseas. Kind of like how Soda Stream use different gas cylinder threads in different countries.

[@bricknplay]

I saw one in the Aldi, and thought about that you will definitely do a video about that 😂

I recently bought a few to power my rovers, they use 36V hoverboard wheels (I got a lot of motors cheap but no batteries and controller). The batteries are great I 3D-printed a socket so they are easy to change. Quite a good source for decent standard battery packs for a budget. ALDI also claimed to support the battery system for the next years. One is used in 20V mode to power a DC-DC converter and the jetson Nano.

[@bigclivedotcom]

Keep in mind that these do not have onboard ability to shut off power when a cell gets low.

@@bigclivedotcom good point I wonder if the ID or Temp Pin has an error state for this case. For the rover it is no problem since you want to monitor the input voltage anyways.

[@PaulSteMarie]

Those gate resistors are actually a third leg of the voltage divider. I suspect they are doing some level shifting to bring it within range of the ADC.

[@d.t.4523]

All that design time. All that buildout, and all that reverse engineering. Just to hear the sound it makes when it hits the trash bin, when it dies. It's not like you can replace cell 4 when it goes bad, they just shut off the whole pack. Keep working. Good luck! 👍

[@johndododoe1411]

Unless the microcontroller refuses. This should happily recover after cell replacement.

[@kevtris]

Trying to figure out how the battery voltage monitoring part works and I think I figured it out. The Vgs for those FETs is around 2V, so the voltage at the drain needs to be 5V-2V so 3V or less. The large series resistors would accomplish this I think. In regular operation, I suspect the micro is tristating those gates, so the G-S resistors are closing all the FETs off and the 1M is ensuring they stay near ground. It would then pull one of them high which will turn one FET on, and its series resistor with the battery limits the voltage going into the drain to around 2.5V or less I'd think. The G-S resistor would act like a pullup too, injecting some current into it. that part is pretty strange still. I would expect the resistors to get larger as you go up the ladder but the schematic shows otherwise.

[@wherami]

this was very complicated. amazing considering how cheaply the part costs but it supplies a lot of power.

[@labiadh_chokri]

thanks for the schematic I get the value of the thermistor and used a 10k resistor to get the 20w led projector np-rwd-20r working with 18v erbauer battery . they said compatible only with active energy battery :-)

[@robertadsett5273]

Hmmm, the 2N7002 has a 5V gate with typical threshold of 2V1 (max 2V5). I wonder how much of that divider work is keeping the gate drive within acceptable range.

[@AUATUWVSH]

nice charge level indicator with the Zener diodes, ive seen one on a Ryobi pack that used a TL431 per LED

[@lightcapmath2777]

Most impressive. this is why you ROCK! on such clarity. Cheers and happy holidays..O! any chance on seeing another "candy calendar" video????? DVD:)

[@landrec2]

Great work!

[@Z-Ack]

Pin 4 is the set output regulation for overcurrent draw from the battery which is always too low for the tool you plug it in to. Ive had to remove that cap all together on every battery ive made using those diy boards..

[@stevenspmd]

Well done! You continue to up your reverse engineering game. Chineisum vendors beware!

[@adammorris3082]

Woah- A bit more in there than I thought there would be- These are actually looking like they are worth the £19.99 for the whole drill- I'm tempted to get a few just for the 18650 cells alone - I could knock up some decent 10/13s 10ah packs for the scooter if you get a decent amount of charge cycles. Thanks for another good vid. ATB :)

[@wich1]

Yeah, was wondering what the quality of those 18650s is like

[@crazygeorgelincoln]

Good to know about the reset procedure, wonder if it bricks itself like the Ryobi clone packs .

[@gregorythomas333]

Damn...that was very complicated!

[@ericblenner-hassett3945]

Interesting that they would use a " reverse resistor ladder/voltage divider " to ensure that the FETs are off except the cell they are checking. Also of note that they used opto-isolators for a form of low speed COM ports to each other. The thermistor issue could be a way of not having either MPU have some complex way of both reading the temperature as well as the charger reading it.

[@AintBigAintClever]

The resistor ratios in the monitoring schematic at 6:27 may help it make sense, they may not:- E: 6:1 D: 5:1 C: 4:1 B: 2:1 A: 1:1 Interesting that a 3:1 ratio was skipped.

[@billhall1983]

I have a lawn mower that runs on the 40V. When I use that battery in a drill (20V) it does seem to last much longer so I think that they do go in parallel. Really good video. 🙂

[@bigclivedotcom]

They do. I've tested it.

[@lmwlmw4468]

Great work.

[@Orxenhorf]

I'd think you'd want to connect the pull down resistors to their own path to ground separated from the ADC line by a diode perhaps.

[@Steve_Wardley_G6JEF]

Great video as ever Clive. I usually like to let the adverts run if it benefits the channel but the one following your vid was 49 mins long. Just had to chop that one.

[@bigclivedotcom]

Only watch the adverts if they interest you.

[@simonwatson2399]

Once the MOSFET is on, the gate capacitor voltage is going to be summed with the voltage on the high side of the 1M sense resistor. It looks like the ratio of the gate resistor and battery resistor has been tuned to ensure that the boosted capacitor voltage is never high enough to damage the MOSFET or the microcontroller. I assume the specific values were chosen as the cheapest for that ratio.

[@stevenfaber3896]

Great series, but there is still that question out there of if there's comms between during charging. If you have or can access it, after the holidays when the returns come in stock, maybe finish off the trilogy?

[@bigclivedotcom]

Spoilers, the charger uses both signal connections, and can switch current to each section independently.

[@MrDbone75]

A very merry Christmas to you all from Wellington Somerset

[@pa4tim]

I think to see what it exactly does, you need to calculate all voltages and currents. But you need Vg for that. The current from Vg through the gate resistor and the 1 M at the bottom adds to that flowing via the drain resistor and the 1M. If the output of A,B etc can sink current you need to count that too. It is also possible Vg is not a fixed value (via an opamp ? ) but different for each mosfet to get enough Vgs to switch it on. And the voltage over the 1M resistor needs to stay within the range of the ADC.

[@johntickle3120]

Nice one Clive this has thrown all sorts of issues for me trying to make one charger fit all project. I have a Dewalt drill and a Ferex drill. The Dewalt has the BM smarts in the charger and the ferex in the battery. Up to now I have a 3d printed shoe that conectcts + _ ve to the Dewalt from my cc cv bench supply simple stupid and balance leads to connect to an Imax balance charger if required. I don't have a Dewalt charger so not aware of its internals. I think I have to go back to the drawing board as the Ferrex charger is dumb and the Dewalt charger has some smarts not sure if its duel voltage i=either. Love to see you reverse engineer other makes of tool chargers batteries. Thanks for your excellent video😎

[@bigclivedotcom]

There are so many ways of controlling the charge that you might have to reverse engineer many different communication protocols. In a way the dumb eBay tool batteries are so much easier with their onboard protection.

[@paulwright8378]

I use a solder sucker on those terminals when I'm refurbishing a battery an after I put new cells in I solder wires to the connections so I don't have to fiddle about getting the old terminals inline with the circuit board

[@frankowalker4662]

That's a very complex circuit. :)

[@jimsvideos7201]

You wonder how many hours of forward engineering went into this.

[@SeanBZA]

PCB looks like it has ICSP header, so the reset is needed to allow the processor to be reset, and then on coming out of reset you can enable programming mode, likely to allow writing into the data storage area of the EEPROM for things like allowed capacity of that batch of cells, and also set the ADC calibration, plus a serial number for the pack. No balancing, so the weakest cell determines capacity, and the dual thermistors, along with the transistors, also allows use with tools that have "dumb" monitoring controllers, simply using the packs as supply with a thermal sensor, or an intelligent pack (likely the 40V tools) that use the comms to read things like capacity and allowed current, and to thus extend battery run time considerably. Probably uses the tool being connected, and thus pulling up the NTC line to 5V, as a wake up, using an internal comparator to interrupt the micro, and starting a routine that first attempts to communicate by disabling the thermistors, then looking for a communication down the NTC line, signalling via the ID line. Nothing coming in within a second it then assumes a dumb tool and switches the thermistors on, and then also sends an IR pulse to the high side to wake it. high side then simply feeds battery state voltage down slowly, and likely the method for dumb tools is to switch off the thermistor drive, and let the tool think the battery is very hot, shutting off the tool. smart tools likely get a rough battery capacity gauge sent periodically, with the microcontroller probably running every 5 seconds in a loop to read, so thatit can spend most of the time asleep.

[@lesliesoutham7396]

Just an observation as I'm not into electronics , the ratios of the resistor values may have a bearing of the otherwise arbitrary values of resistance. Could it some how point to each particular battery in sequence relating to common ground?

[@sparkyprojects]

The ntc connection must connect with the charger so the battery doesn't overheat Maybe that 3rd mosfet in the chain also signals the charger

[@Gazereths1234]

Beer and tinkering with circuit boards, sounds like my kind of night!

[@Lukas-jt3sz]

Do those dual voltage batteries have any advantage? Either you get double voltage and half current OR half voltage and double current. The power stays the same

[@Farmelle]

5:00 that looks like a long form D2A circuit. Similar is used on the old 80s/90s home computers to produce video signals.

[@tniemi]

I love the schematics!

[@nicholashacking381]

I was in Aldi, today, and they had an angle grinder reduced to £9.99 ... amazing. At that price I couldn't afford to leave it on the shelf. Now, I've always tried to avoid buying rechargeable tools other than the brand that I normally buy, so that I don't end up with a load of incompatible batteries and tools. But an angle grinder for £9.99 is not to be sniffed at, so a 20/40 V battery and a charger went into the basket too. When I got home and unpacked my shopping... I realized that I'd bought a corded 240V angle grinder, (still a bargain at £9.99) and a battery and charger that I really don't need. Ah well, now I can buy Aldi battery powered tools, when they are on special offer.

[@handlesarefeckinstupid]

I've somerimes bought a lidle tool, perfectly fine if you use one very rarely for a job. Still using a corded lidl angle grinder after 6 years as i rarely use it and it would be pointless spending a lot on one. Let's be honest the ecoensive brands aren't much better sometimes.

[@SeanBZA]

@@handlesarefeckinstupid Still using an angle grinder I got in the 1990's, Black and Decker. Not used much, but still does a few jobs a year for me. There were 2, one was killed by a builder who burnt it out in 5 minutes by pressing so hard the motor dropped to around 800 RPM, and running it till the smoke billowed out. The Bosch one of around the same vintage is also still in good order, and each has typically only one type of disk on them, one grinding, one cutting. Had a few cheap Ryobi ones that were bought, used a few times then either given away or failed.

[@franktuckwell196]

I do not understand 90% of what you are talking about, but i relish your opinions as to wether an item is actually, good value for the money?, or worth avoiding at all costs. Happy Christmas to you and great new year, cheers.

[@opjose]

I would love to see you do a video on the small Lithium powered car jump starters. Most tout 24000mAh battery packs or larger, yet there is no possible space for any battery that large in those devices. The max power draw values are also ridiculous.

[@bigclivedotcom]

I've looked at a few and shorted one out to measure the current. They use parallel stacked plates in their lithium cells and can put out hundreds of amps for brief periods.

[@Mike-H_UK]

I think that the pull down resistors for the MOSFETS' gates could have been connected to 0V thereby removing the through current causing an error for the ADC. NMOS devices do not mind if the gate is lower voltage than the source - it just depletes the channel a bit more.

[@robertadsett5273]

Some N channel MOSFETs are only rated to -1V or so but the 2N7002 isn’t one being rated to -20V. I’d be more worried about low gate voltage. You might get significant Rds on variation. That might explain the divider variation

[@rizwanmohammed5339]

Thanks for videos keep them up I was also wondering since i have a lipo charger would i be able to charge the batteries with that without opening them in set of series by passing the charge through the top of battery like the original charger

[@bigclivedotcom]

It wouldn't allow balanced charging of the internal cells.

[@BrianG61UK]

Re the possible RC reset circuit. It could also be for a clock oscillator. Knowing the R & C values would help decide which is most likely. I hear the dislike of using processor to monitor safety critical voltage and temperature but maybe the processors have a watchdog timer built in.

[@JustinHunnicutt]

I'm not sure if it means anything but the ratio of the resistors for each cell are 1:1,1:2,1:4,1:5,1:6. Seems like it might explain something? Maybe something with adc range? As seen at 4:16.

[@mtreis86]

How many bits does the ADC output? I'd guess they're trying to have the steps between batteries be evenly spread across the ADC's range.

[@bigclivedotcom]

The Ryobi clone version indicates a 12 bit ADC.

[@bexpi7100]

If they had chosen lower value resistors for the voltage dividers used for sensing, not only would they get less risk of noise on the dividers by increasing the current flow, but they could also use the measurement resistors for balancing. I suppose they could still be using the measurement resistors for balancing, but it might take a while to significantly influence the state of charge of an 18650 with just 1 µA of current.

[@tonfleuren3536]

That would have been a lot smarter; however it may be impossible to discharge one of the higher cells in the pack, without also discharging the cells below it. Maybe there is a clever arrangement (possibly with more MOSFETs) that would allow this. I was wondering about how those MOSFETs would be driven, considering the microcontroller can only output up to 5V. Consider the gate of the top MOSFET; the gate does not need to go higher than the pack voltage, the gate needs to only be higher than the voltage drop across that bottom resistor. The 2N7002 needs about 3V Vgs to turn on fully, so as long as the voltage across that bottom resistor is less than 2V, it can be turned on. The whole arrangement is rather complicated to analyse logically, because all of those gate-source resistors become part of large voltage divider is the outputs that are not being used are driven low instead of high-Z, and the output driven high sources some current to the bottom resistor. When it's turned off, the Vgs should not go below -20V, which is violated, since 5x 4.2V = 21V.

[@johnrhodes3350]

I have a Parkside drill that made a loud clack sound when releasing the trigger. I loaned it to a friend and it came back worse. It would stop or cut out if turned on its side or not operated with a particu5 orientation. I took the gear box apart only to discover one of the orbital gears was missing. Not damaged or fragmented, but totally missing. It was evident that one had never been in place. I could tell this by the distribution of grease, and clean bare patch where the gear should have been. I've got a photo if any one is interested. Put it back together and it still sort of works but cuts out if you don't orientate it exactly, which is not convenient. I have another smaller Makita which is doing double duty.

[@anythingyouwanttvmr.anonym959]

That circuit Is like a passive balancer. The temperature, over charge voltage etc.. of Each battery cell is monitored and control on MCU.

[@kevinmartin7760]

That is a pretty wacky circuit for the a/b/c/d/e sampling. The ratios of the gate pulldown resistors and the corresponding battery resistors sort of follow a pattern: A 1:1 B 2:1 C 4:1 D 5:1 E 6:1 but that jump skipping 3:1 is strange. The battery resistors themselves seem to follow a pattern at first, for A, B, and C they are all around 3M, but then on D it jumps way up to 7.5M and on E plummets to 1.8M. Actually, that value for E seems almost implausible since (I assume) the output across the 1M resistor should be perhaps 2-4V, wouldn't you need the battery resistor at E to be perhaps 4-9M? Is the E output of the MCU capable of sinking current to pull the voltage down? Actually, that can't work that way because it would just cause the MOSFET to cut off... Maybe the A/D input of the MCU can take voltages higher than its supply voltage? Whether this makes sense at all depends on how the 5 outputs from the MCU are used (+5 active/Hi-Z inactive?)

[@dougle03]

A multiplexing ADC into those binary IO's currently used for mosfet switching (i2c) would have been a simpler option, and whilst still two IC's would be required, one would have been cheaper than two MCU's. This looks like an exercise in hardware design snobbery, rather than getting the job done in the simplest and most efficient way. Equally, to go to all that trouble without adding any balancing does seem a very odd choice, especially when capacitor active balancing is super cheap to implement with minimal passive components. And what's with that NTC connection pulling double duty? Why does the battery and device need access to the NTC's when the battery 'almost' has its own BMS (Sans juicy MosFet switching) with comms to the device. A very odd design indeed; thanks for doing this Clive.

[@rpavlik1]

Some of the tool batteries that have "communication" use it to allow the tool to exceed what would normally be an over current limit.

[@johndododoe1411]

I see very little snobbery. To allow the tool to run the batteries in series or parallel requires some way to run the two half circuits either isolated or with a clever circuit to reconfigure its own operation for P, S or other load config. A serial port with optos makes efficient use of the most common on chip communication feature. As designed, this leaves the main BMS job to the separately sold chargers and tools. The controllers basically multiplex all the battery status data onto a single pin to keep connector price down.

[@abitofabitofabit4404]

Speaking of efficiency, voltge dividers with a 1Mohm output impedance would impose an uneven 1-5µA continuous draw on the cells. A user or stockist would have to charge the pack frequently. With switches embedded in the voltage divider, it is possible to disconnect all the cells' dividers, reducing the BMS's parasitic current consumption by orders of magnitude depending on how often they are sampled. An idle battery isn't very exciting, so hourly sampling might do.

[@dougle03]

@@rpavlik1 Would an over current damage the cells? An over current situation would presumably only lead to damage, thus allowing the tool to over load the cells surely should be avoided... unless selling more battery packs is a marketing goal of course...

[@rpavlik1]

@@dougle03 an overcurrent without a tool attached is called a short circuit and could cause a fire.

I think Dave Jones from the eevblog made a video about a micro controller you can get for 1 Cent preprogrammed. It blew my mind you can get it so cheap (in volume). With this design you could also do some balancing (like you showed in a previous episode), but i guess they did not bother for that price. Perhaps that's why it looked like that, it's a stripped down version of a balancing battery pack. ;)

[@bigclivedotcom]

Padauk microcontrollers. The cheap ones are OTP (One Time Programmable). Sadly, the universal programmers can't usually accommodate those chips.

[@Naturafaidate]

Hello and thank you for the very interesting video.... Can I start an Aldi drill, for example, without using the battery by directly connecting the 20v to B1+ and B1-?

[@bigclivedotcom]

It needs a 10K resistor from the sense pin to -ve. But that will defeat any low battery protection.

[@backgammonbacon]

Its a voltage divider ladder? So the microcontroller just measures the voltage and knows what battery its reading?

[@Darieee]

would be very chocolaty to see a scope view of how those MCUs chat during their time alive ❤️

[@wtmayhew]

This battery isn’t as mean a Dyson stick vacuum battery. If the Dyson controller detects even a transient anomaly, it commits suicide and won’t do anything but blink a red LED 32 times even after the anomaly is cleared. Perhaps rigging a JTAG connection would work, but what data to send? I eventually just ordered a replacement battery.

[@dauerwerbesendung7045]

I love it! Can you recharge the battery using a DC-DC power supply? I have a 24V solar setup and want to cut out the losses from inverter and battery chargers. Is there a save way to do that? Looking forward to the next part of the series! 🤩

[@bigclivedotcom]

It's better to use the official charger. It might be viable to adapt one to low voltage use.

[@hoverbovver]

Did I miss something? No balancing FETs? I thought a balancing circuit was essential in every Li pack. Or does the charger do the balancing? There don't seem to be enough connections to achieve that though.

[@bigclivedotcom]

No obvious balancing.

[@johannglaser]

I'm confused with those NMOS for the voltage monitoring (around 6:02). How can a 5V MCU output turn them on, if voltage on their source is higher than, say, 3V (i.e., the gate sees only 2V, compare 2N7002 VGS(th) min. 1V, typ. 2.1V, max. 2.5V, and with the goal that RDS is negligible to those MOhm resistors)? Also, if A..E 0V except for the one selected channel, then all gate resistors would be in parallel with the bottom 1M resistor. Except if the MCU would let the output float, which might also work.

[@kimchristensen2175]

ooohhhh! Now it makes sense to me. I didn't think about the gate resistors effectively being in parallel with the 1M when their associated output was low. Hmmm... With the correct combo of high, low & Hi-Z on the A,B,C,D & E lines from the MCU, it should be possible to put the ADC voltage in the sweet spot (2.5V or a bit less) for each tap on the battery pack.

[@Black3ternity]

Regarding the regulating / monitoring circuit: Maybe the values are uniquely chosen to have a "clear identification" in software? To be able to do further calculations without referencing to fixed pins / values. Additionally you said there are two processors. Do you now if they are in a failover-state? Could the pack be run with only one chip in place? This would make this pack pretty safe and reliable so that the software can't glitch out or burn down the whole pack when one processor has failed. Edit: For the potential bidirectional communication over the NTC: Maybe the tools have thermistors / sensor circuitry in them aswell? For overheating motors and such things. This makes the pack basically the brains of the operation and the tool fairly "stupid" as you have shown in the Angle grinder teardown. This would make excellent marketing in my opinion because they could justify the (presumably) more expensive price of the pack by labeling it "smart pack" and just a "dumb" tool.

[@DatBoiOrly]

my guess just from looking at it in bits is that it's 10 18650's pushing around 40v's with a battery protection circuit then thats split into four terminals 2 going to a buck converter dropping it to 20v's in two prongs then 2 connectors thats direct from the battery that gives 40v's then the final pin being earth

[@dozer1642]

As a hobbyist, this battery pack reminds me that I’m just a hobbyist. 😳

[@ChoppingtonOtter]

Love how you foxed their sttempt to hide the processor serial

[@nothingbutthetruth7900]

Let's say I wanna rebuild my double battery can I just use these cells alone ? Fantastic work mind blowing 👏🏻

[@bigclivedotcom]

That would depend on the circuitry in your old battery.

[@nothingbutthetruth7900]

@@bigclivedotcom I'm very new to this stuff but basically I'm just replacing lithium 3.7 to the same3.7 18650 ? As I have a DEWALT battery that's 50/50 and a ebruer that's 100 perfect but only have DeWalt so using the other one just as a donor

[@ElvenSpellmaker]

After seeing your soldering iron video I spotted it in Lidl and the 20V battery too and so I got one, but I've yet to see the charger for it! I wonder if there's third party ones...

[@bigclivedotcom]

The chargers are usually in stock. After Christmas the stock should return to normal once the shelves have been cleared of seasonal stuff.

[@ElvenSpellmaker]

@@bigclivedotcom I'll have to keep my eyes peeled then!