BMS (Battery Management System) || DIY or Buy || Properly protecting Li-Ion/Li-Po Battery Packs 

Your SMD soldering skill has become so much better than your previous one. Appropriate amount of flux was given. Louis Rossmann would be proud of you.

Thank you for taking a look at my BMS design. I have a new version 4 that I am currently working on which removes the higher current drain on the cells to less than 1mA, the software is also more flexible.

Just FYI, your videos got me through a seriously bad time in my life and I am thankful for you. This hobby saved me and God provided!

Well that was unexpected! Great video as always. Thanks for featuring my channel.

Really pleased you got use out of my fork of the code and found the extra features of use. Thanks for featuring my channel and great video.

Fantastic incredible job I love these diy or buy videos🙃

For smaller projects I still like using a TP4056 wired parallel on each cell or cells of the series pack so for a 2P 4S I have one TP4056 on each 2P = .500mAh each cell x4 Chips using 4 separate phone chargers for isolation and you can use the single cell protection strips for unprotected cells so they shut down before under voltage. Cheap and works.

I like the way you present everything clearly.. Even a simple formula for all to understand.

I am a biologist, but your videos have taught me so much about circuit design. Thank You!

When Scott does something he does so that it just looks perfect and nice.

Loved the extra balls of solder (04:04) on the commercial unit straight from the store! So much for build quality control...

Duuude lets see this BMS in action! Make a charger for lithium ion batteries next! That'd be so dope

Commercial BMS : I'm simple and available. DIY BMS. : it's complicated

I have been experimenting with these type 18650 packs for about a year now. I have built dozens. I use a fused nickel strip on most of mine now, all of them that have more than a few cells in parallel. I accidentally did short one while assembling it and all of the nickel fusable links glowed and melted, it was scary, but spectacular to watch, but it worked and potentially prevented a bigger problem. I just tested the cells and put new fused nickel strip on the top and it was good to go. I wish I had had a camera running. My point is that they are, in my opinion a worthwhile safety feature and insurance policy. For batteries in buildings, I have been building metal boxes for the batteries in case of fire. I do not have such charging and power draw as most of mine are working for small solar power collection and lighting backup. For me, heating of the batteries and thus needing to cool have not been issues. Every once in a while, if I have my thermal camera with me, I will look at them and see if any of them are heating, as they fail they get warmer when heating or cooling. I made some of my first packs from very old salvaged cells as those cells were very cheap to practice many of those cells were on deaths door, so I got to see failure modes. It is a pain in the neck to dissassemble a pack for a failing cell, so I try not to use cells that are too close to failure. I have taken to adding load disconnects and do not charge mine above 4 volts as I am dissatisfied with the BMS performance of the Ebanium and Amazonian varieties I have tried. I would like programmable LVD and HVD, but it seems that unless you build your own they are made out of unobtainium.

Its funny i was searching for these videos for the fist time about 12hours ago. and here you go making one basically as perfect a timing as you could.

When making power bank from parallel batteries I would use Schottky diodes between the common junction and the battery positive to prevent weak battery from pulling down the strong one and thus exhausting / draining the overall power. This also provides protection against defective batteries. I would also use protection circuit (simple one) to prevent over charge and/or protection against accidental short.

Scott, you are the best I ever seen about electronic modifies. I want to be great at understanding electronic devices like you.

That ad spot in the middle was probably the smoothest segue to one I've ever seen! :P

Perfect episode, I was trying to build my own BMS for quite some time, but everytime i failed. Thanks for the power od your chanel now I'm able to build one on my own :)

I needed this, and here you are. May you live long.

I think it would be really great if you could order for example ten times the components you need for a project of yours and put them up for sale in kits consisting of everything you need except tools. Great job on all your hard work. I'm definitely enjoying the results.

"Draws quite a bit more current". Of course! What were you expecting? Wi-Fi isn't exactly low power. And that's an extra in comparison to the commercial BMS, which can be removed to make them comparable, and save 3 €. In fact, you could also try NRF24s or other low-power solutions, combined with an ESP gateway, in order to make it better.

currently working on my own arduino based system. Don't have a main control board yet, but I have working cell modules, and they only draw 0.11 uA when idle and 2-7 mA when transmitting.

What is missing in both commercial and DIY BMS is the current limiter. Most of the Li-Ion can be charged with only 1-3A and to me it'd make sense to add a current limiter so that it's enough to plug a DC power supply to charge and balance. So you don't need an expensive power supply as yours.

Thank you dear Awsome!

Always Love your handwriting skills and of course your knowledge base

You should do video about reflow ovens! You do so much surface mount soldering, it might be worth doing a DIY or Buy. Nice video by the way.

You're videos are best of the best and provides much more knowledge. After watching one or two video I have just become your greatest fan. Keep it up always. ❣️

I always BUY mine. I aint got the... Stark: what? Time? Me: The patience.

can you do a video on how to test a BMS to verify it functions properly (completely disconnected from batteries)

Don't you just hate when you accidentally build a lipo battery pack🤣👌

Oh this was great. When you mentioned 1A of power, that rang with me and my project.

Maybe compare DIY high capacity powerbank with commercial product ? Cause I want to build one in future. Also try to salvage lithium cells from old notebook battery

I have been using the diy bms project for a year now. The work Colin H has done is great. Tied right in to my grafana setup.

Great Scott! this fellow is left handed.. I always knew he was brilliant!

When I see Great Scott, I already know the video will be great .. as Scott.

Great vid. Scott!!!-This is a passive balance/power bleeder-How about active balancing so not to waste power?

Great Scott is becoming... "Greater and Greater" Scott. Awesome videos

Thanks to greatscott,Im now great at soldering!!

Best BMS explaination on youtube yet ..... Thanks scott

I am hoping to see something eventually come out that is nearly as comprehensive as a Batrium system but more adoptable for smaller projects. One specific need though is for higher current output through any of these BMS solutions at the small side. With the attractive nature of building high capacity portable battery packs, the ability to push a lot of amps is a must have if you also plan to feed the power into an inverter, especially if it is only a 12v inverter. I am starting my first project and have some of the 4s 40 amp BMSs on the way and a dedicated charger like what they sell on Vruzend. Should be sufficient for what I am up to but I am watching and looking at things a lot. Still not seeing that magic solution yet...

I learn so much from watching your channel, thank-you!

Well, you did not test nor compare the "cheapo" BMS as a comparison. which is what feels missing to me...

You should get a hot air solder and buy the stencil when you order the pcb. That solder job would have been done in 30 min and look perfect.

I just got my DIYBMS pcbs yesterday! Still waiting on some components from china, but I will be making a 12s version to balance chevy volt modules.

Nice explanation on the "Buy" options... one point I'd make is, that the DW01 works in tandem with MOSFETs, not "simple" Transistors. Yes, I know, MOSFETs technically are transistors, but you did make a distinction, when talking about the big Power MOSFETs... so... just my two pennies on the matter.

Sponsored by the pink markers ! :p Awsome video, like always

So some of the BMS you find that look like yours and are sold on several platforms (amazon, ebay, or aliexpress) do not actually do as they claim. I bought one almost identical to your only 3s version... it almost ruined my pack. I have a nearly perfectly balanced pack (50mAh variance out of 30 000 mAh total). The issue is that is somehow managed to make 2 of my cell banks (3s16p battery) were discharged to 0 volts and one was at 4.3 volts... Not good. None of my cells had any measurable self discharge before this happened, and I have been attempting to find out what is now causing the self-discharge, whether it's the BMS or if the cells now have a self discharge. I didn't even get one charge out of the pack. Only the initial charge was usable (I charged each cell to full to test for self-discharge and so they'd all be the same SoC for assembly). I saved the pack with a small active balancer, and thankfully the over charge and over discharge protections all worked on the BMS or it would have started my pack on fire. Maybe mine is defective, but I'll have it investigate later. In any case I would recommend an active balancer on any large pack. They actively balance at any voltage so they can be used even you limit the charge to between 20% and 80% to extend cycle life... and they're a LOT faster than bleeding off the cells since every amp you drain from the highest cells goes to the lowest cells so it's almost like balancing twice as fast... while making less heat. Though some of them have low current so I just get one that has low drain ( less than a miliamp) and leave it connected so it can just always balance and I never have to worry about it. Realistically, the DIY BMS with the 1 amp bleeder resistors is faster than cheap active balancers because of that giant 1 amp of current... the bleeder resistors in most commercial BMS boards are way way smaller and are thus going to be slower than active balancers and are only going ot activate at a set voltage which is set by the BMS circuit rather than programmable software.

Well i think this is a good alternative for some projects but this doesn't provide balance discharging....It can only be used for balance charging .. Can you please also guide for balance discharging from the same bms..

You are so clear in your explanation! Perfect! So DIY for powerwall, and commercial for small packs...

will you make some projects on audio electronics and please make a video on how to make a NPN common emitter power amplifier.

Instead of joining the cells in packs permanently by soldering or welding, I join the cells with strong mini magnets. Then I can take the pack apart easily whenever the cells need charging. This way I can charge a lot, or all the cells at once in parallel, sharing the same 4.2 V voltage. No need for balancing when parallel charging. Each 18650 cell is current protected by a fuse. After charging I can (re)assemble the cells in series/parallel packs with magnets in different configurations, depending on the voltage and current demands for any desired purpose. This is the most cost effective, the safest and most versatile way of using and charging 18650 cells. All you need is a good quality power supply, that can handle a constant current according to the number of cells to be charged in parallel. I charge at 300mA per 18650, so a 10A power supply will charge about 30 cells at once. Obviously, it takes some time to take the pack apart and to reassemble it. But when using magnets this can be done reasonably fast.

It’s better to buy only, because cost will be less 👍🏼

Dispensing solder paste by hand or with a stencil, placing the components, and putting in a little toaster oven will save you a lot of time. Use your soldering iron only when really needed.

Aren't there simpler DIY BMS's available? No need for all those fancy-pancy super features for a simple home made battery bank.

This is the best series from great scott

Awesome video 👍👍 To make BMS can we use TP4056 charging modules for each cell and then solder them on one PCB followed by connecting input wires? *Will it work fine?* If yes, this will be the cheapest and easiest way to do that..... Plz reply??????

Wow! Very creative indeed dude. Your video tutorial (electronics) is the best i watched so far. Every information of the components, schematics, mathematics, technics are all there making it a stop learning experience. Some words i might miss due to accent but its not a problem. You are imperfectly perfect. Thanks and stay creative.😀

Hey you should do a diy or buy wireless Qi charger

I bought my 14s 52v bms from ebay 1 year ago and used it on my ebike battery. To anybody thinking bms's don't work, you probably didn't buy one. I made my own battery pack and spot welded the batteries together. One day the battery died on me really quick and i couldn't understand why. Two of the spot welds were disconnected and the bms tried to compensate so it shut the whole battery down which in fact saved my ebike battery. 30$ well worth it

Interesting....🤔 Thank you for the information and keep it up!!!

Those commercial units are becoming better and better, as well as cheaper.

long story short: unless you have a microscope for smd sodlering and chirurgical precision, go for plug&play commercial BMS :D

I believe the DIY is the best option especially if you are hoping to making a product for future use. Once you fully understand the commercial vs the DIY, you will be able to fully appreciate a potentially better design for future use. Thank you, for your excellent presentation. By the way, Series is not the same as Serious (ha!). Thank you again

Great video! What is the maximum amount of cells you can use in series with this system?

Wow! I've just discovered your channel: I wish I'd found it before. Excellent in-depth stuff, well filmed and explained. Thanks.

8:46 "as well as the female headers" - solders male headers :D

The biggest problem I see with all these bms is a separate charge and power connection for negative. It makes it tough to do a lead swap out with lifepo4. I've found one bms that will hopefully work for an automotive application. Otherwise these designs limit your project capabilities. If you do have a bms with -c and -p do not connect them together as this will override the protection function for charging.

This is a mismatch, its like a go pro vs dslr both useful cameras with different application, what could have been the comparison should be that BUY vs DIY (of the same build of the buy).

Amazing video my only concern is that because it's connected to the internet someone could set the voltage to high for the cells and maybe even cause a fire

Love me some lithium ion battery panks

nice work mate, but i just want to say ive bought loads of cheap bms from china/ebay and ive never had one fail

18 $ shipping, nice)

Thanks! All the things I've forgotten since basic electronics class.

Watching this video after got burned by a lipo battery pack.. 😂

It makes sense to activate BMS when charger is connected i.e. it should draw power from external power supply.

Hmm I just made a lithium ion battery _and_ I have no idea how I did this 😂 guess I'll watch the other video.

So the interesting thing here, is that some of the more popular applications that you would use a LIPO/LIION Battery for would be for use on a PEV - Electric Mountain Board, Scooter, and so on. So we can imply that the Speed Controllers in many of these applications have their own Voltage detection, Current Detection and limits set for draw (Think VESC 4.XX and 6.XX) we can ideally make our own charging dock using this method. by taking the examples from the use of the hobby style RC Car packs you can use this DIY BMS as a desktop Charger for your packs as you return from your excursions, rather than having them permanently affixed to your pack.

Can you please say in a future vid: 2 cells in a series relationship, you could say, are married. Plzzzzzz

Been so curious about BMS's lately. Thanks for a great vid

Shame you haven't actualny explain HOW do design a BMS

I think you should have used stencils to apply solder paste, probobly then you would have two working boards. Correct me if I am wrong

next up: "DIY or Buy: BMX"

As this is protecting your safety is this really a good idea for a home made project? An alternative would be to buy one ready made and learn how to test it to make sure it works. The test rig is an interesting project.

spot on with DIY BMS being for powerwalls and such. It seems to have better front end functionality than most of the cheap to midrange BMS units, which are mostly focused on providing BMS functions more than front end features, so you can end up blind on how your batteries are actually doing with most purchased BMS units - which isn't ideal for something that you want to closely and carefully monitor. Meanwhile anything that's portable, you may not care as much about what individual cells are doing, and just need a relatively simple (in terms of features) BMS to keep the cells relatively healthy, and shut down the current flow in the event of something dangerous happening (which you can later check into on a bench). Good stuff, very interesting.

Hi. One drawback for BMS like these is the available ballancing current. There are so called active ballancers, cheaper and more expensive (which get better feedback from people) but the better ones are like 25usd for 7s. My idea is to use a regular bms for all 'over'-protections on discharge, and to take 7 dc-dc buck cc cv converters, and maybe 7 1S BMSs for extra protection, and make a separate charging "circuit", where I hook up 12V (or whatever buck accepts) as input to ALL buck converters, each of which charges single string to required voltage, and a 1S bms after each dc-dc buck, doing extra safety. This way I can actually get a ballanced battery, with whatever max "ballancing" current is allowed for a single string of cells. It would cost maybe 10-15usd overall. Does it sound ok? And if it does sound OK a DIY BMS could have built in feature like this ;)

Hi, thanks for your great Videos! I like them and learned a lot from them. But I would like to comment on two things ins this videos. 1. Your SMD soldering is good but I would recommend you to get some very fine tipped tweezer. When you soldered those bigger packages onto the smaller footprints you need to grab them tight and guided the into the solder. That way you can get a better solder joint and be faster. It looked kind of funny when you tried to poke the in the right direction. 2. Bootloader: A bootloader doesn't program fuses only. (That part I also don't know) But he programs a certain firmware in a special sector of the µC which tells him how to act on certain signals on his pins and where he needs to put this data. Keep up the great work and your great videos! (BTW: I love your handwriting and your drawing skills!)

I think you're the man, that's what I think! What's your college or university background? And most of all I think you should shoot a video telling people why you chose it and why you love (and understand) it so much! Congratulations!

You are always Great MR.Scott......

From research to practical applications is a long way. Technology is like that ! It is not easy

I like how this guy says series and lithium Serious and lifium

But the DIY BMS does not feature the charge control MOS FET. So it cant switch off the charger when all cells are full. I think a BMS should be able to do that.

Wow , Holy Scott ,…… nicely explained project,……. Please do some 4S BMS ´, Lifepo when possible ,.

just imagine the time it took you to solder all of those components. A commercial wave solder machine solders all the components in the blink of an eye as a wave of solder runs over the bottom of the board in an instant.

Wow. My brain just exploded. Nice job, man!

My boat solar is constantly charging all day and discharging all night so the tiny balance current of the ebay and amazon BMS do not keep up as the cells become unbalanced during charge and discharge. A BMS with a true one amp balance current capability is going to be very helpful in preventing some cells from becoming overvolt when charging.

Muhteşem bir çalışma olmuş hocam. Batarya yönetim sistemleri önemli bir konu. Yazılım ile de çok verimli batarya yönetim sistemleri yapabiliyor ki en büyük örnek Tesla bataryaları.

Congratulations for 1 million subscribers 🍻

I think for custom, mission critical packs, building it yourself might be the best answer, more control for critical functions.

Have a PCBWay ad on a JLCPCB sponsored video.. Something seems very wrong about this..