USB Battery charger + 10A BMS - Interesting, right?

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🔥I want a battery cell charger with USB connector easy to use but also to have an output of 10A, that's why I've made a module that combines the TP4056 with a 10A BMS at the output.
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00:00 Intro
08:51 Thank You
Like share and subscribe to motivate me. Thank you
#electronics
#learning
#circuits

[@ELECTRONOOBS]

Join my Arduino Course (Spanish): bit.ly/2JY8icE My Tools: bit.ly/3uv8bc3 Help me on Patreon: www.patreon.com/ELECTRONOOBS

[@th3godofgenjutsu]

your soldering skill still sucks

[@evgenidimitrov2639]

The breathing is noticeable and a bit annoying but that's only me. I'm not trying to offend you in any way so please don't get the wrong idea. You can do whatever you think is best:). With that out of the way you can try While recording the voice audio for the video to have a mute switch. Basically after each sentence you press the mute switch which you can program to have a hold function(while holding mic won't work) take your breath and continue. This will increase your product quality. Again that's in my opinion so do as you wish. I'm just giving my point of view.

[@wileymarm0t]

This is exactly the education that I need to understand projects involving high current and 18650 batteries. Thank you!

[@pawelutwin3439]

finally someone explained it to me. This is what I needed. Looking forward to seeing material about BMSes

[@nextmove1428]

This was SO helpful. I was looking for a power system for future DIY projects!!! Thanks for this!

[@MitsuZer0G]

Just what I was looking for yesterday! Thanks for the video!

[@ranaharsh365]

I prefer to use USB type C Power delivery feature to get higher voltage for 2S/3S/4S instead of boost converter. & also TP4056 is just a general purpose IC for DIY projects. I suggest using CN3795 IC, a multi chemistry, Multi cell battery charging IC including MPPT for solar charging. In combination with normal BMS, this system can literally charge any type of battery pack with USB type C.

[@AmneYoshi1410]

thats what i tho

[@lifeai1889]

nowadays there are modules like tp4056 but it can do 2s or 3s with both 5v and can trigger fast charging so it hhave buck boost converter inside

[@AmneYoshi1410]

@@lifeai1889 so its work like usbpd?

[@lifeai1889]

@@AmneYoshi1410 I'm not sure it's pd or qc but it dose use typec and it can auto adjust voltage

[@eliteman125]

Does multi chemistry just mean that I can do slightly different voltages as different chemistry's have slightly different nominal voltages?

[@sinisterkage256]

I'm so grateful for your work. Keeps me going on my projects

[@raymondmichael4987]

Thanks buddy; Will be waiting for more videos on the topic. Your channel is amazing 😮

[@fully_retractable]

Thank you for posting this, I was looking for a way to charge a 2s setup via 5 volts usb, but I couldn't find any modules. From the looks of it it's going to be a component setup. You made a new fan today, thank .

[@alexnewton3376]

Brilliant idea man. Good job and thank you for sharing. I will try your PCB

[@deborahsimpson4968]

really nice to have stumbled upon your channel. congrats on your good work!

[@danblankenship5744]

Yeah, perfect timing. I have also been searching for this type of board and saw that they don't exist. I needed a high-capacity ultra-quiet 5-volt (USB out) battery module. So I opted for a 2S-4P battery configuration with a buck-converted output. I had to piece together different circuits to meet my needs. It is very cumbersome with three switches and a battery level indicator to ensure I don't over-discharge the cells. Since I didn't include a boost converter for the charge source, I am using a 10VDC wall wart. The first switch is the charge/output switch to route my 10VDC charge source to the 2S-BMS. The second switch is used like the on/off witch. It is part of the DC input plug. When the wall wart is disconnected and the charge/output switch is in the charge position, then the batteries are isolated and it's essentially off. The third switch is a momentary switch used to activate the battery-level indicator so it will not drain the batteries. What I feel there is a need for is this and I would purchase them from you today: Fast rechargeable, high-capacity battery packs with USB output and adjustable DC sources. It would be nice to see the battery level, the output voltage, and the output current with a simple push button. The output should be a low-noise DC voltage from a linear regulator. It could be also current-regulated for the ultimate version with an optional fan for cooling. The charging voltage could be from two sources. A high-current fat charge could be from a wall-wart and a slower low-current source could be from a USB port with a boost converter to match the 2S or 3S configuration. I think if you built a board with a choice of 2S or 3S configuration options, you could sell thousands of these boards.

[@pratikbawankar8066]

I explained it very well. I liked your way of explaining. 😊 I subscribed

[@Gengh13]

Can't wait for the BMS video.

[@-mose191]

Thank you!! It seems like i found another information vid for my electrical projects i make! As its mu hobby!

[@mussim2919]

Wow! Love your channel! A lot of great informations!

[@-MrDontCare-]

Great video, just what I need.

[@pwal8468]

I'm looking forward to the bms conversation. Hoping you will also talk about bms that can and can't charge and discharge at the same time...

[@makas005]

Thank you for reassuring me i am not crazy. I was looking around Ebay and Aliexpress for a 2S Charger together with a BMS Circuit. Exactly like you stated, it was either a charger without protection or a BMS without charging IC. I thought I was too dumb to look for the right parts, but now I'm glad someone else has the same problems finding a suitable module.

[@T.R.E.D.]

This has been my experience EXACTLY. I would be so happy to have this solved, safely of course. For me it’s 3S.

[@randimadilshan4010]

@@T.R.E.D. I have this 3s type c module but it outputs 13.4v.is that bad for 3s bms cells that rated input voltage 12.5v

[@T.R.E.D.]

@@randimadilshan4010 that is pretty interesting, you might link or share that module. I can’t imagine what that would be but would be interested in checking it out. Especially that voltage. We can check it out.

[@randimadilshan4010]

@@T.R.E.D. Bro it is the same one like in this video

[@T.R.E.D.]

@@randimadilshan4010 oh my bad I thought you were saying you found another board.

[@alfstewart2592]

i literally had this same problem the other week. very good idea

[@renelefebvre53]

C'est ce que je cherchais depuis u bout de temps . Merci pour le PCB .

[@leehewitt9559]

Really interesting video. Good information. 👌

[@fufjjjjdyk1308]

Thank you very much for your videos

[@ELECTRONOOBS]

Glad you like them!

[@philsponsel3824]

super useful, thx! 🙂 like the others i would also be interested in a chip which has all the protektion + high ampere out + using the higher voltage USB-C features

[@temyraverdana6421]

A great lesson. Thank a lot

[@Leif_YT]

I like the powerbank ICs from Injoinic and others these days. Probably not the best pick if you really need a lot of amps, but for general electronics they include a lot into a single ic with very few discrete components.

[@usnaveen]

Great video May god bless you.

[@kucingkeren8042]

I really like the last module with multicell usb C, it really simplified my project so that i just need to add battery level indicator and a bms, I have used this module for my 12v Portable speaker project and it work so perfect and reliable. I thing this module is kinda new or underated bcs i see not a lot of online seller have this module & not many youtuber dicuss about this module

[@T.R.E.D.]

What is the module called? I have a robot that I want to be able to charge a 3S battery internally, with XT60 or even better USBC. Without having to add a balance charger port. I’ve been searching for months trying to find a solution for this, I got excited that you seem to have some experience! I’d really appreciate your input!

[@tamasstummer2888]

Good video, thank you!

[@kikihun9726]

Check out the 12v ups switch modules too. They are pretty cool, can switch to wall power if the battery goes under 10v. Pretty useful for a constant running Rpi server on a solar system.

[@josholin31]

I read "solar system" as is. Not as a solar panel system. Lol

[@technology.ki.duniya1]

Thank you👍🏼

[@mortamir1791]

Just ordered these boards.

[@ronniepirtlejr2606]

I have 38 of the Panasonic NCR18650B batteries. Awesome batteries!👍 The spec sheet says they can only discharge 15 amps "continuous" safely! I just thought I would mention it to you since you were showing a picture of this particular battery with a discharge rate of 20 to 30 A. next to it. By the way you know way more about Electronics than I ever dreamed🙂👍

[@volodumurkalunyak4651]

Good luck drawing 15A from Panasonic NCR18650B. Thise are probably rated at only 6.7A of discharge current. 15 A - way to much for those.

[@ronniepirtlejr2606]

@@volodumurkalunyak4651 I agree! I found several different data sheets let's say the same thing. Only a few say 15 +

[@shakerileiwat4341]

Thank you 👍👍👍

[@TediChannel23Ja]

Very informative 😊

[@fruitcup01]

Nice video, hope you got your boards, and some company considers your idea. Maybe make the max. output current selectable.

[@Kumodot]

Btw you got a new follower ! ❤

[@HakAtIt]

Also most type C PD charger will output 5v, 9v,12v and 19v{or 20v}. With this you could use a PD type charger and avoid a boost.

[@taham6757]

yeah i plz i got lost choosing the bms and collecting data on the internet this would be so helpful

[@johnshaw359]

I bought a 10A strip 1S BMS and then connected it to a USB-C charger module for USB PD and a protected 14 AWG 2.5 mm DC jack output on a broken 30,000mah powerbank to repair/salvage/upgrade it.

[@satyakumar4229]

Thank u for giving right solution on right time. Good luck wish u many more.

[@Rees3901Gmail]

I reckon you're on to something good here, if you can design and provide a general purpose 1-4s battery charger that offers all the usual protections (over/unders etc) combines USB C with PD input, ( with selectable outputs like the PD decoy boards) you could be the founder of the 'next' TP4056 chip for makers all over the world!🤩

[@ELECTRONOOBS]

It would be great!

[@keithking1985]

I'd love a module like that.. 👍

[@user-qu1nh8hl8q]

It would be really great if you sell your design of the boosted module@@ELECTRONOOBS 😁

[@Puzzicanello]

​@@ELECTRONOOBShi, thank you for the video! I came across the same module you show at the end of the video, but i don't get how to connect it to a bms (i'm talking 3s). Should i connect the same you did with the tp? Positive to battery positive and negative to the board negative?

@@Puzzicanello That's a hell of a good question and NO ONE answered (LOL). It would solve my problem too. I'll copy and paste it, maybe some good soul answers...

[@StanleySeow]

great video, can u do a video on all the component break down of the USB booster that can charge up to 4S with 2A, thanks

[@JonathanDeWitt1988]

Andrei, This was another great video. I ran into this issue a couple of months back when trying to build a battery pack for my RC car I was working on. I wanted to USB charge my 18650 Li-Ion batteries without removing them from the holders because the holders are prone to breaking with repeated removal and insertion of the batteries. I asked around on electronics groups on Facebook. They didn't have a solution. So, I came up with something that works. But it isn't as elegant as the solution you are suggesting. And your suggestion would use less parts. I already tried sharing a Google drive link to my schematics. But KZbin removed my previous comments. So, I'll describe it here. Basically I designed and built a battery pack PCB that has one SPST main power switch and one DPDT mode select switch. Each battery can be switched from 2s in series and independent using the mode select switch. When they are independent the batteries are connected to the battery terminals of a TP4056 module (there are two modules, one for each battery). So, when I want to charge the batteries I turn off main power and then switch to independent before charging each battery using a USB cable for each. Then I disconnect the USB charger cables and switch back to 2s in series. Then I can power on my loads. To protect the batteries from deep discharge I have an ADS1115 reading the voltage of both batteries and the second battery for my ESP32. I do some math in the microcontroller to get each battery voltage independently. I then have my ESP32 programmed to let out a chirp from the RC car's buzzer and kill the outputs if the voltage of either battery drops below 3.0 Volts. I also transmit those voltages to the Android app so the user can see what the voltages. This is not as elegant as the solution you are suggesting. Do you think you might develop the 2s version of your circuit in the future? Thank you for looking into this. Another great video!

[@Enjoymentboy]

This is interesting timing as I've been working on the same thing with the same modules. So far I've been able to over together setups that work for me but the one thing I've not had any luck at is wireless charging with a QI receiver module. I found one with a USB-C connector rated at 5W that does work... sort of. Once the BMS reaches 11.79V the output from the QI drops to 2.24V and NEVER goes higher meaning the batteries never reach 12.6V cutoff. I found one QI receiver rated at 10W but I outright refuse to pay $20 fire it just to test.

[@jparky1972]

I'd love to see a video on how to convert an old battery drill to LIPO. I've seen a few video's in the past by other creators. But they never seem to do anything with output ampage or with how to charge a battery configuration that may be set up as something like a 3S2P pack.

Great tutorial! I came across the same module you showed at the end of the video, but i don't get how to connect it to a bms (I'm talking 3s). Should i connect the same you did with the TP4056? Positive to battery positive and negative to the board negative? Thanks a lot.

[@ahmedelboghdadi5328]

Great video

[@gabrielllorens]

Thank you for the video! Will the board be usable as a charging board for a laptop-like behavior? When switching between battery charging and battery usage (and viceversa) is seamless?

[@sham1234567891]

Great stuff! Is it possible to find a bms that allows selective connection/charging for multiple batteries from 1 to 6 cells or more?

[@StanleySeow]

Can u do reviews of different types bms n what chips are they using , pros & cons of each bms, thanks

[@dennismugweru2325]

Great teacher 👏👏

[@dennismugweru2325]

Learning from Kenya, Africa

[@mr.backbencher5892]

Thanks dear. Alhamdulillah learned very important lessons. Allah bless you.

[@chloeleedow7250]

Usb c pd can do up to 20 V 5amp and more if the cable is rated for it. You're obviously intelligent and deliberately left it out to keep it simple for none pd or pps supplies yes or? Perhaps you could recommend in another project one that fast charge and whatever rate the input can output to battery to the maximum the battery supports. This would be super useful I have a 5 or 6 or these from an old battery pack that the controller died I think and would love to repurpose them for a led torch since no led rechargeable torches fast charge that I've seen lol. Cool video though thanks.

[@seanz2907]

How would you implement the 2-cell charger talked about at the end? Would you still have to alter the Mosfets like earlier in the video? How should the USB PCB and the bms PCB be connected and what changes should be made to implement everything onto a single PCB? Working on a project this is just what I need but I'm stumped on the implementation.

[@daijoubu4529]

The DW01 protection IC found on those TP4056 boards cuts off at 2.4V not 3V

[@nayanpatel145]

As you mentioned in the video How many amps of current will change the battery by the 1s battery charger made by you... Hoping for a early reply... Thanks 😊

[@ranganatennakoon]

Very interesting vedio. I used Tp4056 in prallel and its works wall. it can change 1S battery pack more than 8A.

[@JohnEdwa]

18650 cells can also have integrated BMS boards, they mount on top of the negative end cap replacing that connection.

[@stinkycheese804]

Yes and those are usually best avoided, because they can cause intermittent conduction, and have a fairly low current limit. It also greatly limits which cells you can choose if they must have that. Frankly I only find the protected cells useful for flashlights that don't have a proper cutoff and will cause parasitic drain even when the light is turned off, so it was not enough to just depend on the forward voltage of the LED to not drain the cells lower than that plus the Vf over the regulator IC or transistor(s) in series.

[@keithking1985]

Your final module print would sell well. I'm saving this video for your gurber file. 👍🇮🇪🙏🏻

[@message2prateek]

10 amp output at BMS is excellent, but which boost convertor do you suggest that can output a high current at 5 volts e.g. for driving multiple servos?

[@brandenbc31]

I am super interested in making my own battery charger just like you showed. Currently Im using the 4s version that comes in 1-4s you show at the end but i definitely need to upgrade to include the BMS and unde rvoltage cut off. Do you have a schmatic a 4s BMS and the 4s charger? Im super busy with other parts of my project but im hoping in about 2 weeks I will beable to dedicat the time to cimbining these circuits. Any help finding these base schematics would would be very appreciated! Thanks! I look forward to the BMS video to come!

[@JonnyWaldes]

good stuff. I'm working on 3 cell 65 watt power bank and 100W 4s power banks. 100 watt charing and 100 watt output. ~$14 modules on aliexpress

[@PowerScissor]

I know it will sound dumb to most people, but it works for me. I just hate the hassle of charging every single thing with it's own USB connection...so instead, I just make all projects have a fast, easy way to swap 18650's. I just always have 18650's ready to swap...and then I can charge everything externally in a higher quality 8 bay charger. It's a lot of swapping, but for me it's easier than dealing with a cable and then waiting for it to charge. Some things I have to climb a ladder to swap, but I'd still have to plug in a cable I figure otherwise. You can also easily keep track of the internal resistance of your cells individually and pull out of rotation when they make a big jump in IR.

[@P.A.T.]

Not dumb at all. I also do this. It’s safer and easier.

[@PowerScissor]

@@P.A.T. Let me guess that if you're not going to charge a depleted battery for a while you storage charge it first to nominal voltage? ...and don't charge it fully until you know you're about to to need it. Did we just become best friends?

[@P.A.T.]

@@PowerScissor i think so😂😂😂

[@robertrobert2981]

Good idea I'm not some who leaves comments either I believe what you looking for is on Drone battery's. 4.5V USB CHARGER but the battery do have a short life. Although that depends of the class of the Drone My Typhoon Q500 4K well the battery's Are 12v It would be nice if I could change it with USB

[@jaishankarm5920]

USB PD can delivery upto to 20V 100W. USB PPS allow us to custom voltage and current output limit. Can you please try this method also??

[@mavic-mark8858]

Did you ever have any made and tested ? If so will we be seeing a video?

[@finnpfreundschuh194]

Hey, First of all thank you for your Videos. I am studying electrical engineering in Germany. How much of your knowledge did you learn in your studies and how much would you have to teach yourself? What tips do you have there? I don‘t learn much about that in my studies. And some of my professors are very bad.

[@avibank]

I was wondering why there isn't a board like this already the other day. It seems like a no brainer.

[@bobsoft]

Panasonic NCR18650B, Max. continuous discharge current: 4.875A

[@matteobedogni5724]

I guess that you can have some problems in case you're using your device while it's charging, depending on the amount of amps needed

[@Kumodot]

Thanks for the video ! I have s personal passion project I made years ago, but probably need an upgraded charger circuit. It’s s tiny handheld arcade (3d printed). It uses 3x18650 cells and I would love to make it right and upgrade the system to use the new raspberry pi 5 which uses USB c and suck more amps. Also I would like to have fast charging on it. Would that solution in the end works for my project ?

[@abc121xyz]

what about battery to the 3602a a mosfet between battery and load and the output of 3602a to the gate of the mosfet? that way 3602a will sense undervoltage and cut the gate?

[@barbatmn]

Which do you recommend for making a small battery pack to power 5v LEDs? I’m looking for a solution for LED ligh boxes. I’m thinking 4-5 18650s in parallel and a charging circuit that can output 5v.

[@electronicdiy1120]

Can you please explain more about how to connect 4s battery pack to type C module

[@hippie-io7225]

Excellent thread! Also consider using the FS312F-G to replace the DW01. (thanks to "Great Scott" on KZbin) The DW01 over voltage threshold is 2.4V. I prefer the 2.9V threshold of the FS312F-G. Some of the batteries I build go up to 13S, yet what you are proposing is quite useful.

[@lolsypussy]

Exactly. The UVP of the DW01 is useless for the TP4056.

[@hippie-io7225]

oops! I meant low voltage shutoff. The DW01 turns off when battery volts is 2.4V. whereas the FS312 turns off at 2.9V. A much safer volts for LiIon.

[@StanleySeow]

Thanks for highlight the DW01 chip drawback 👍👍

[@sarcasticfpv3862]

The pinout looks the same so just replace it with the DW01 is enough? Because 2.9V sounds way more safe

[@hippie-io7225]

@@sarcasticfpv3862 I goofed by saying Over Voltage Threshold. The FS312F-G will stop discharging the battery when the Lower Voltage Threshold is reached. That voltage is 2.9V The DW01 will cut off at 2.4V. For some lithium batteries, that is too close to cell death. Over-discharging (battery volts too low) is a major failure mode for lithium batteries .

[@iambenmitchell]

I really want to make my own battery bank as I find the ones on amazon to have low quality cells. I am thinking of making a 4s 3p (12x 21700 cells) battery pack and want to have a few 65w USB PD connections and have it charged via USB C too. I've found a bunch of different boards on Ali express that can do these functions individually, but It seems messy and I'd love to do it with 1 PCB. However, I cannot find anyone on KZbin talking about USB PD 3.1 or 3.0 and QC + other protocols. I can only find people making trigger boards. It would be awesome if you could make a PCB design tutorial like you did in this video, but implement everything in 1 board such as a 4s BMS + PD, etc

[@marcodalcanto7941]

Very interesting! Is it possible to recover an MBS from an old laptop battery?

[@myhomelab]

u can also use tp 5100

[@keenanrvndr]

So the only thing needs to be replaced is the MOSFET in the charging module? If so, can you please be specific what is the needed MOSFET to have the 10 Amps output? I'm working on this too, but on flex pcb

[@cardriverfreerider9783]

As far as I understand, the main problem with your solution is that you can only charge one battery (1S) with up to 10A current instead of the recommended 1C current (for a 3000mAh Li-ion battery, the normal charging current is 3A)

[@FennecTECH]

I’ve been trying to get a 1S but get higher voltage out of it. I have not found many devices that boost 3v up to 19v at reasonable currents to charge an laptop.

[@user-tx7gf7uc8q]

Hi my friends, if I could give you a hug well I would. this is the best video seen since my internship in psychiatry. I am a battery salvager who uses opus and xstar chargers....can your method charge an unlimited number of cells in a single charge please?

[@Kingshukpalchoudhury]

Why not use a 1s bms with hight current rating. Now let the b+ and b- of the tp 4056 module be connected to the p+ and p- of the 1s bms, and connect the battery to b+ and b- of the 1s bms, and take the load output from the p+ and p- of the 1s bms? If the tp4056 board is the one with the dw01, then overvoltage protection is there by both the tp4056 and the 1s bms module, while the undervoltage protection is provided with the 1s bms, and with a higher current limit too. Can be charged with standard inputs into the tp4056 ..

[@-_Robert_-]

Can you build 3S and 5S BMS with USB C PD type charger ( also with no current limit but undervoltage protection? )

[@shoumikahmed6373]

Hello, Some time ago you told that you are working on a lithium battery charger discharger. Any update about that??

[@MrJackfriday]

did you receive the new designed PCB yet?

[@c.schandra2134]

Hey why not add a current adjustment for protection, if micro electronic goes bad they may pump upto 10amp leading to fire....

[@peaceandlove5855]

what circuit you recomand me to convert 3.7v to 1.5 or 2v with up to 4A max ? thanks

[@alokraj824]

Bro please design a pcb with type c charging port to 4s lithium phosphate battery

[@sheshraodhandale]

Please continue this with lion bat capacity tester by uno

[@AdamTheBot]

I never knew this tp4056 charging module has over discharge protection .

[@marcsmith2342]

How can you charge multiple batteries in parallel? Do you need a specific BMS?

[@rnelias]

why not use an IP5328P? I think it checks all the boxes you've mentioned.

[@dibaluk6616]

Nice Vedio. i got quection, i want to make power bank for external camera flash (6v) and i make one using DC-DC Buck Converter but problem is when i trigger the flasher batterys getting hot then burn the Buck converter. any suggestion please.

[@raymondmichael4987]

Any updates for BMS tutorial?

[@lprophit]

if i have a project thats power supply is 12v 500ma 6w and i have a 12v 65000mah which of these options would be best?

[@prakashdutt1520]

Hello Sir, Can I charge 3s and 5p battery pack which is around 11.1volt &10000mAh with 8:52 chargers like this directly connected to BMS? Or do I need any other module in the middle of BMS and charger to get my battery charged? BMS----> charging module---> Charger

[@connorhoyle2926]

what mosfets did you use i cannot find "4804nt" mosfets anywhere

[@edrianloisarborilla4602]

Hi mind me to ask if you have sample battery to power raspberry pi

[@orange_tweleve]

What exact type of amps are we talking about when you say 20 to 40 amps ? At what voltage ? Because there's no way you can have 30 amps from a 3000mAh li ion battery. To pass true 30 amps you need some thick copper cables too. I never understood what amps these electronic components mention.

[@ELECTRONOOBS]

Maybe 30 is kind of extreme but 20A for sure. The Li-ion Power Cell permits a continuous discharge of 10C meanning that an 18650 cell rated at 2,000mAh can provide a continuous load of 20A (30A with Li-phosphate).

[@lazydogthetechnician6695]

Sony VTC4; Molicell p28A just to name a few. Also, when you put a few 5 Amp cells in parallel, you get up some crazy high Amps. And, yes, you are correct, those require some serious interconnects. Don't use the cell holder he uses in the video @3:10. That thing is not even capable of 1 Amp. Little tiny wires, and those rivet connectors don't sit right on the +4V.

[@tenlittleindians]

@@ELECTRONOOBS That explains how they are able to make battery packs for electric bikes, skateboards and scooters out of 18650 batteries. I've been wanting to convert an electric lawnmower over to lithium 18650 cells but have the same problems of figuring out current draw, charging and low voltage limits while also having cell balancing.

[@stinkycheese804]

Why would you think that? If you have a battery specified for 20A or especially 25A, in certain high load situations (for example a nearly stalled cordless tool), it can reach 30A, though with an expected voltage depression from the cells, which in turn may also reduce the amount of current the tool draws, but it is manageable. Recognize that you don't really need especially thick copper for short distance power transmission. Yes you will suffer a little voltage droop, but as long as it does not cause excessive heat which causes damage, then there is always "something" that is the bottleneck in the circuit and it wouldn't be practical to design everything for infinite current. Such is the burden of the designer to estimate, create BOM, test the prototype after calculating out the most cost effective strategy to get the most out of the design without diminishing returns by spending significantly more. Plus, you are only thinking of single cells in series. Two 18650 in parallel of a high current cell design, can exceed 30A. More to the point, if you are buying generic chinese designs, you don't really want to barely buy the margin you need, just in case there were things overlooked, like the fact that those transistors can't handle their rated current without more PCB to 'sink heat away than they provided, so if you expect to be able to sustain 20A, with cells rated for that, you probably want a generic BMS to be designed for more. There are some people who like to claim the opposite, that you should match the BMS overcurrent threshold to the battery rating, but in some designs there isn't a need for this because if higher current causes voltage depression then that limits the current anyway and a true short circuit would be higher than your 40A spec'd BMS anyway, but again, test rather than trust.