Most BMSs (Battery Management Systems) don't cut it... I Built a BETTER One.
Video Overview & Insights
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AWithZ P30C Supercapacitor Spot Welder: https://amzn.to/4nekGlV
Battery Management System (BMS) design is critical if you want your lithium-ion projects to be safe and powerful. In this video, I show you the only correct way to build a BMS – and prove it by pushing over 50A per 18650 cell for more than a minute without overheating. We’ll dive into how a BMS should control voltage, current, and temperature faults, why cheap AliExpress BMS boards fail, and how my custom BMS development board uses the Texas Instruments BQ77915 to control the power path the right way.
In .au too. Great video. I had a little chuckle at your delight when spot welding bus bar with a copper strip inserted. I bought a Fnirsi /20 battery powered welder especially interested in the claim of weld .1mm red copper.
Well.. After spending days working some things out so relatively easy for my pay grade, I found that it was necessary to get the resistance down pat. With the probes on the nickel strip and the Cu .1mm sandwich things started working predictably I should try heavier just didn't have on hand. This system also worked well on non stranded Cu wire but stranded wire wouldn't fuse to itself well so only attached a few srands. Works on brass shell casings maybe .2mm. Also Stainless steel fly screen or small dia wire.
Do you do school presentations /edu?
I’ll explain voltage monitoring, MOSFET selection, hysteresis, balancing circuits, and why GreatScott’s and ElectroNOOBS’ designs don’t actually protect your pack. You’ll also see my test setup dumping the power of 9 laptops into a heater, real thermal camera footage, and my battery pack built with Ampace JP30 high-performance 18650 cells and welded with a P30C supercapacitor spot welder.
If you’re into robotics, drones, RC, or DIY battery packs, this is a must-watch before you build your next project.
Is there any BMS in AliExpress you would recommend. In my country custom pcbs aren’t cheaply available.
Video on difference amplifiers:
https://youtu.be/qNeOWJz2oUw?si=frN1RIR9bSkq1njQ
Where can I find a really reliable 40A BMS that is close in size to 50mm x 22mm x 4mm? Trying to connect 3 - 18650 Molicels in series. I can't find ANYTHING reliable. They all suck and stop working after just a couple of minutes of runtime because my amperage is too low for what I'm needing to run. Out of 6 identical BMS's, only 1 works the way I need it to. Any suggestions? Size matters! lol
00:00 Intro & HIGH POWER testing
01:34 Explanation
I’m a senior ECE student at UMass Lowell and love this project—really impressive work. I’m designing a motherboard for a servo quadruped and was wondering if you’d be open to sharing schematics (totally understand if not).
05:47 Sponsored section
06:20 More testing
Youvdid an absolutely fantastic job! My respect! Our world needs people like you.
07:00 Battery pack explanation
07:26 Sponsored section
Engineer here, anyone who says ''there only one correct way'' to do something does NOT have vast knowledge or experience about the subject, trust me, as you get more experience you will see that the range and types of projects very by a lot depending on the requirements and budget, knowledge and experience shows you how best optimize the design to match the desired requirements.
08:00 Conclusions and announcements
Disclaimer: The content in this video is provided solely for educational and entertainment purposes. Lithium-ion batteries, high-current circuits, and DIY electronics can be hazardous and pose a risk of fire, injury, or death if handled incorrectly. Any statements about products, brands, or technologies reflect my personal experience and opinions only. I am not responsible for any harm, damage, or losses that may result from attempting to replicate, modify, or use the information shown in this video. If you choose to work with similar systems, do so at your own risk and follow all relevant safety guidelines.
where can i get this bms from?🙂
More User Perspectives
No link for the BMS?
@richardharris5819Great video @h1tec, could you help me out making a bms for my company. We are a battery manufacturing startup company based out of India
@indrajeetdate9086after building a new battery for my boombox (8s 15ah lifepo4) i used a reclaimed Victron medical grade bms. it worked to balance the pack on the initial charge, but the first time i powered up the 'box, the short circuit tripped! i guess my 200w amp capacitors are over the 60a burst current rating. so now i either need a better bms, or to wire it in such a way that the startup currents are ignored by the bms. my current idea is to run a relay off the output of the bms that switches the main power before the bms. this means i lose the short circuit protection, but keep the low voltage protection.
If you ever go into higher cell count systems, I'd love to see it! I'd buy a Haase Industries BMS 😁
The fact that your bms doesnt have active balancing makes it useless though.
@catnipaddict126Super impressed about your research. How do I get your schematic. I’d like to put on a smaller pcb
@geek.vill8028You are just like me, but with more knowledge about power electronics XD
I like your design, in fact, I think I'm gonna use it.
I need a bms for a small BT speaker and it's gonna be powered with a 3s2p pack
your knowledge very interesting. can we collabrate together since I would like to study further your BMS design. can we communicate further via email? need your email address please. thanks
@mohdshafiebinbakar1595Hey, great video! Maybe I have missed something in the Video but how exactly does your BMS handle the balancing of the cells? I am interested in making my own BMS for the same reason as you, but I want to be able to charge the Battery with more than an amp. Most "cheap" BMSs have too little of a balancing current to keep the cells balanced during charging. How did you manage the balancing?
@BastelLöterI am new to this, but how would this be configured for lifepo4?
@josephgraham1847can i get the schematics for this bms ? it will be very helpful
@nithinmathewjoji7471I love this concept, and I am in desperate need of a BMS like yours! But I'd love to see some actual schematic files that would make it easy for me to modify and alter it! Or just any documentation at all!
@BRORBITWow… nice video man❤
@TronixHubwatching this made me realize how behind I am, even though I have alot of experence.
@FlatMcdonaldsSpriteI do PCB design for work and I'd love to see your board up close. PCB design for handling power is tricky and might require in depth knowledge depending on switching frequencies.
anyways, nice video mate - keep it up, cheers from Poland!
'how many sposors can we fit in this video?' "Yes."
@_TiredofitGaming_Lithium cells are damaged when charged above 4V, reducing their lifespan. How could a battery management system (BMS) be designed to charge the cells to a maximum of, say, 4.05V?
@LappingMasterSo glad I came across this. Been trying to make some simular but bit smaller for 2 cell max for iot devices. Everything i found is to large or sketchy so been working and looking at datasheets for months and also settled on this ic. I'd love to see future videos schematics and or maybe ways to incorporate into smaller projects. Thanks for the amazing video and information, I know its a load of work. Definitely earned my sub and cant wait .
@kaylajason8917It’s no wonder I can’t ever focus on electronicals, always seem to get distracted thinking about sh*nts.
@crash284you could stick it in a freezer, or on a cold pack, for under-temperature?
@super_doop3i like u. u crazy. 👏🏼
@Eriiiiiiiick✔👍
@sawajiri100are we supposed to stich a proper schematic from screenshots?
@Mr.LeeroyGimme that BMS!
@RIPpropsbrother can i get the schematic file of your bms .
@IFELSE8700The only thing that I wanted in a "perfect" BMS board is to have power path management built into it. To put it simply, when a power source is plugged into the BMS, it cuts off power from the battery to the load and change the power path from the power source to the load. Hopefully without interuption. Wait a second, this is basically reversed UPS, LOL. How is this useful? Well, I always try to have any battery powered device plug into the wall to prolong the battery lifespan, I don't need to operate my Bluetooth speaker on battery when its on my desk with a socket right next to it. Yes, this feature can be implemented with external components but it will be very convenient if its integrated into the BMS.
@sft1830Use ANT BMS. Does everything. Does not post obnoxious bait videos
@jaleger2295V mount battery
@AbhishekThakuragaFinally, a man that understands what’s going on.
I really appreciate this great work ❤
But hope u open source the project so we can learn better 😘
Max I ask why you added a layer of nickel on top of the copper? Also you should probably solder the BMS probes before spot welding to avoid damaging the cells
@davidcroce555In case of fire, there will likely be an investigation. If it’s found that the source was a battery lacking safety certification, that might be used to deny or reduce payout.
Insurance contracts often have clauses about “use of approved / compliant equipment” or require equipment to meet “applicable safety standards.” If your battery is non-CE-compliant, it might violate those terms. Please follow the new EU Battery Regulation (EU 2023/1542) if you are in EU.
The "Enriqueeee" at 4:34 killed me 😭😭😭😭
@6marvilThe higher RDS on resistance of those cheaper fets correlates with a higher voltage rating. I havent used that particular infeon fet but similar 30V DS skus I've used in projects have shit the bed from relatively small inductive spikes, there wasnt even an inductor in the circuit, just a resistive load being switched off and on at 2khz. The parasitic inductance seems to have killed it. Using 2 much cheaper higher voltage fets in parallel has been far more reliable even though the nominal current rating is less than half.
I understand that the fet isn't acting as a switching node in a pwm circuit, however given how dodgy so many chargers and even loads often used are, I'd be concerned about frying it nonetheless.
The higher resistance also limits inrush current, increases thermal mass of the switching element and increases surface area to dissipate that heat. It does increase the risk of failure as a single failure results in a short, but I've seen expensive systems use the standard multi-fet arrangement at the negative terminal AND a much larger single fet behind them that latches off if certain secondary thresholds are exceeded. Really fancy systems also often have a burnable fuse that the IC can trigger physically breaking any circuit.
electronoobs just copy greatscott
@tanjiro3285I would buy one of these bms, I'm specifically looking for a 3 cell bms for my project
@ironsquirrel89Wait....your BMS has no active balancing??? That is the biggest part of the BMS features....the features you are focusing on won't save the pack once it goes out of balance. Does it just lock up the pack once a cell is too far outside the window? Or does it just run cutting the charge/discharge to the weakest cell?
@fookschoolThe intro got me. Keep your interest up – you’re on a phenomenal path
@Kost_JobuschSomebody needs to do an exorcism on the YouTube comment section. I can literally feel myself get pulled straight into offensive/defensive mode
@diggledaI've been looking for this for awhile
@chrismorrison8510Why do you criticize the power losses of voltage dividers, but then use a difference amplifier that has a quiescient current of 100uA? Did you isolate the charging ICs in your discrete solution so that they are only drawing current when a charging cable is attached?
@captainoneayeTypical DIY trying to spend like 20 years of discrete work when 1 IC solve all your problem.
@chengfengwang5386This would be great for the EV race car enthusiasts.
@sloqlapCould you also please give the board a direct dc out, without any pd in the way, as I personally am interested in not the power bank as much as the power supply for custom projects…
Edit: of course I could get the dc out from the battery but this would bypass the under voltage…