DIY Rapid Build 18650 PowerWall Module project - design & testing

[@zachhoy]

I respect how transparent you are in your findings! Even though you sell products, I feel that you are truly a battery enthusiast first.

[@wesKEVQJ]

After trying to spot weld 8 packs with 65 batteries each, I am so ready to spend money on traditional battery holders and blank pc boards to solder the holders to. Etching is easy. All the boards are the same you can use a stencil and a marker. Your boards are probably cheaper or the same as making your own so heck yeah. Your accent brings back good memories from the Navy.

[@mountainman4410]

You give hope to people like myself who just don't have the time or energy to deal with all the complications of building these walls! I can't wait to see these ready for sale!

[@billz4071]

Good testing. There is a problem when you use mechanical connections to the batteries. The resistance between the battery and the terminal will go up when you pull more power. Also, the terminals from the battery clip to the circuit board should be more robust. This is where you need "Hard Connected" cells from the batteries to the outputs. Spot welded connections and larger wiring is needed. Regarding the resistor lead for the fuse, it isn't going blow for any reason. That little wire can easily source 10 or more amps through it. Been that route myself already. Battery technology is scary what these cells can produce in power, while balancing the overheating before a massive outbreak of a fire in present. Remember also, water cannot put out a Lithium-Ion fire. All these electric vehicles are subject to MASSIVE destruction when these cells short or catch on fire for other reasons. Great explanations and testing procedures on your behalf for everyone.

[@unlost117]

I like the "no bullshit" approach you do explaining the good and the bad in your videos man. Great to see honesty and facts. Keep up the good work.

[@DailyWalk365]

Just my 2¢, I would consider finding a battery holder that provides more contact with the battery. Typically I see when inserting batteries in holders that the spring clips are rounded slightly as is the battery terminal. What happens when you put two round things to each other, the contact area is greatly reduced. It's like driving current thru a small wire. It will get hot. You might have to solder or weld the tabs on the batteries for better current handling. Loved the video. I like the way you think out a project and not afraid to ask for help. Smart man!

[@RANDOG1951]

Thanks again Oby Juan Canoby - Garcia :>). I'm running 400 watts newly installed on my 1984 Chevy Van G20. Going to increase to 800 watts. Going boondocking in my elderly years. Thanks for your contributions to humanity. Good Job Maynard. Ola

[@wanderingbox7971]

RANDOG1951 awesomeness

[@ben-yi3nh]

This is huge !!! Its the first battery pack that allows easy replacement of bad cells !!!! EASY WITH NO NEED TO OPEN AND TAKE APART EACH BATTERY WELDING, AND THE RE WELDING THE WHOLE SYSTEM BACK. anything you build with this system will last a LIFETIME. no more throwing batteries because of one bad cell !~

[@mick-sk5lw]

that holder is made out of ABS and has a safe working temp upto 80C. i just tested one that i have using my soldering iron and at 100C after leaving the iron on for 5 minutes there were no visible marks. at 110C there was a slight indent that was hard to see but you could feel it when sliding the iron over it. at 120 it was almost instantly indenting.

[@dantyler6907]

Maybe add microfans for each panel, blowing ACROSS the board. Also, a bit larger fan (same used in other electronic supplies). Finally, venting on the top and bottom of the panel enclosures. Should accommodate lots more heat than massive numbers of these boards can produce. Fans can go a loooooong way!

[@Retinalism]

The quick appearance of high temps at the ends of the batteries is due to the (potentially) poor connectivity of a spring contact arrangement. While it would appear that there's adequate surface area on the battery end and the frame spring contact, nothing could be further from the truth. Moreover, once the spring contacts do heat up they'll warp out of shape, compromising the contact area even more. There is no substitute for properly attached (welded or soldered) wiring when your current profile on each cell is likely to be 2 amps or more. Also, once enough heat is generated in those spring contacts their elasticity will also deteriorate with time. These types of "quick connect" frames are best suited to test equipment applications, but even then, longer duration current flow could still create heat and connectivity issues. There is no substitute for doing this shit properly, especially with these pocket bombs called Li-ion batteries.

[@funposting8912]

Came to post this. I wonder what the energy losses from these things are at day one, let alone day 100

[@cryptonein]

@@funposting8912 So what's the real solution to this?

[@alex-v5j3w]

Scrolled down to post exactly this, I am frightened by these practices.

[@odriew5014]

Use some steel wool for a better connection. Better yet use copper wool although it's much more expensive. Just be careful to keep the wool in the right place so it doesn't short anything.

[@ngrader]

@ztechlabs Just make sure it's '00' steel wool, for maximum destruction.

[@racia4095]

I say you are headed in the right direction. A challenge I would hope you can address is choosing the right BMS that's affordable.

[@johnneilbibera2227]

This is nice. adding heat shrink tube to the long bolt to make it safer, great stuff!

[@jameswyatt1304]

Exactly what I was thinking - simple HST. Also on the balancing pins, but can just one larger tube, rather than individual. The bolts remind me of the buss bars in power supplies for telecom gear, large computers, and such.

[@davidriley7659]

just had a thought about this. What if, instead of laying the batteries horizontal, you placed electrical tape around the 4 vertical poles and stacked the 18650s in vertically. Once you've worked out your exact pattern and how they stack together, you could design a PCB to match, and a small blob of solder on each "output" could be enough to make adequate contact with the battery. you also would use a multi layer pcb so that the top of the battery bank is the bottom of the next level. I just did a quick calculation that the PCB size of a 7 piece holder can stack 33 18650s vertically if staggered. Although your spacers would be double longer (the width of a battery), your PCB costs would be reduced by 1/5th

[@tony_25or6to4]

The sound and visual of Jehu sliding the board across the table is driving me nuts. :-)

[@kcocgibkcusuoy]

Tony P "So, we have this board here..." *Bats board, bare trace side down, around table like a cat* Whhhyyyyyyy?? 😱😭

[@dorhocyn3]

That sound made me very uncomfortable also

[@lenawebb-bey3642]

Tony P you are sooooo right. Nails on a chalkboard!! 😂

[@Stoic-of-Rome]

Theres a lot of us sound aspergers about LOL

[@Tony_P]

Triggered me too. Must be a Tony P thing !

[@tonysshadow]

REALLY appreciate your trials. All the discussion and chit chat in forums from arm chair experts means diddly squat ....till someone like you dives into the deep end of the pool. Thanks again

[@Spartan2x]

I would love to have a large power wall with theses all spread out so that you can easily just pop any of the cells out. Even if it takes up a entire wall- it would be sweet.

[@zodiacfml]

I had a good guess for failure on those plastics. Typing that, I realized that there are more problems with the plastic holders even if you avoid the excessive heat. The plastics will surely get weak overtime and will cause the terminals to loosen which has a set of problems. As mentioned by one comment, they are great for portable applications. I don't have a a proper solution yet but a frame made from aluminum came to mind.

[@JeffKreska]

This has some serious potential. I would love to build a powerwall but I don't have the time to put into it using previous solutions but this, I would do in a heartbeat.

[@guillermomarturetfendt9037]

Do not build this!! The system doesnt charge uniformly all batteries! I will fail and explode with time. Trust me, Im an engenieer

[@dejayrezme8617]

122°F = 50°C 90°F = 32°C Thanks for the video! It's interesting to see that it's actually the connectors heating up, not the cells. PS: Or with a different camera angle it's mostly the connectors... So for a serious power wall you really do need to solder. For smaller applications like for a solar powered shed or van for LED lights and ventilation this would be just great. Of course heating up is wasted energy so you really want to avoid it if energy is scarce.

[@jehugarcia]

Powerwalls never need to be discharged in 1 hour or less

[@dejayrezme8617]

Hmm I wonder if you could use the 18650 holder springs as a fuse wire at the same time? Silly idea of course, but if you'd have these springs using some piano wire.

[@AnthonyPiedra]

I"'m binge watching your videos. I admire your hard work. This is truly an inspirational set of videos -- and you're taking DIY to the next level! Props!

[@jamest.5001]

If there was a clip that just soldered to the board. And use no plastic. Where the cells would fit really tight and make good contact. Beef up the traces if needed. Maybe use thicker clips to hold the cells in and make electrical connections. That is similar to what I had in mind. But I knew the current would be limited. I need more like 5amps per cell. Until my bank is large enough. I'm at 150 ah and 29.4volts. And hoping to have it doubled by the end of the month. Keep at it you may just have the next big thing there !

[@DiyintheGhetto]

They might not be able to handle the current like that But for other projects like led flashlights, small power packs for charging stuff abd and whatnot. Its a great idea. Thank you for the share.

[@neutronpcxt372]

Yeah. These thin steel strips can't carry a lot of current at all. I would not recommend them for big high powerwall operation.

[@mr.e-toy6776]

NeutronPCXT The thin pins are for balancing....the main power goes through the posts on the corners

[@gregorythomas333]

I think Neutron was talking about the pins on the battery holders being too small for the current load.

[@JoeMalovich]

NeutronPCXT if like to see a comparison between these and a soldered or spot welded setup thermal-wise. I have a suspicion they were conducting heat out of the cell. It doesn't make any sense that they would get hot and the tiny fuse wire wouldn't.

[@DiyintheGhetto]

I think because of the metal it's acting like a heat sink for the battery. More wider the metal strip it the more it looks like it's expanding. And i think with the fuse wire. Being a Thin piece of wire. Maybe I'm wrong I have no clue Just a guess maybe.

[@randyfelts4625]

I know you are trying to reuse an existing battery holder but you might want to look at a contact with less resistance. That could help lower the temperature a bit. That, coupled with a more fire resistant material than the plastic might just hit the sweet spot. Then it's just some serious safety testing, some supply chain research, and a good assembly partner and you could do a nice small batch manufacturing plan that would feed a large segment of the DIY market that doesn't want the repetitive soldering job.

[@emmseehammer]

Jehu, will we be able to just purchase (Aussie thinking of shipping cost) the PCB's and source the rest of the bits ourselves?

[@jehugarcia]

Yes this will be fully Open source as well as offering the PCB Fully populated and unpopulated.

[@emmseehammer]

Thanks Jehu, Look forward to the official release.

[@oluwafemioladunjoye6164]

It will be awesome to be able to buy the PCB board. Some of us are novice like that in Electronics and would just like to buy and use.

[@mr.e-toy6776]

That is some great design! I love the simplicity! Keep it up!

[@yoyellow1]

That's nice, will the board design also be downloadable? so we can order/make it ourself, since your shops are mostly USA and give high shipping to the EU id like to create the board myself..

[@tripzero0]

You could also include cutouts with pads similar to the fuse holder so that people can turn it into a 4S or other configuration. I mod'd my pack with a wire from the 4th positive pad back to return positive line to make a 4S configuration. I also attached holders to back so that it's got 8 cells total.

[@FilAmGabe]

This is really great Jehu! You have have done a very good thing for the DIY community. I am am excited to give this a try. What do you think the largest you think this can be scaled to? Thank you everyone involved with this project.

[@briantoribio4245]

I think it is good idea, that pack is very compact and easy to ensemble. I like that because reduce the time to build and see like a very professionals product. Just only need think about the best way to keep the pack fresh.

[@timberthewolf733]

Awesome! ABS melts at 105+*C so 3d printable plastic battery holders might be viable?

[@redandgoldfan3869]

this guy's a battery genius, thanks for sharing!

[@garystinten9339]

A cooling system integrated into the racks would be nice also. Future revision for customization. The futures looking bright

[@studiowebselect]

Not ratted for more than 1c so dont need cooling. Its design for power wall not ebike!

[@MarkLLawrence]

It wouldn't be too hard to add a simple pc fan 3 or four pin port on that board, then it could cool itself using minimal power.

[@boombeachnoob3642]

Gary Stinten power wall module Yay

[@jmonsted]

Stick 'em in a rack (or whatever other cabinet) and put a cheap car radiator fan at the top pulling out hot air.

[@phizicks]

Thanks Justin on a great idea and product, awesome design skills too. Putting many of these in parallel, it can spread the load easily to 1C.

[@MB-lh5kw]

I'm very surprised the battery terminals are getting that hot with only 500ma from each battery, the contact resistance must be quite high , can you measure the voltage drop across the battery terminal and batter clip?

[@webosm6494]

Wasn't it maximum 4.5A per module (18A total). The batteries on the module are in series so each battery is delivering 4.5A. With that amount of current and temperatures I think the voltage drop is considerable.

[@petercoutu4726]

You can also look into getting thermo-set plastic holders for the cells. It would probably be a little more difficult to find but could possibly solve the meltdown problem.

[@PetreAdrian]

some individual fuses would be great - like the one for the entire "module" cause with current design if you burn one "track" thats it. this can make them "reusable". But amazing design maybe you can also make them "double layered"so you can position the holders on both side so one board can run 2P config . just need to make on side a little "offset" than the other, do one side and after the other one - price per cell would go lower on assembly. Still great jooob!

[@demolitionwilliams7419]

Two years later I'm just now reading this.... Fantastic ideas

[@keithforbes8482]

Hey Jehu I want to draw your attention (as well as that of your fan base) to the kweld diy battery spot welder... Designed and built in Germany, priced like a cheaper/ low-end Chinese spot welder, but out performs (by a significant margin) the 2500 dollar multi pulse spot welder where I work!! If you haven't yet done so, you would really want to pay close attention to this clever little machine!! I personally have one, and its the most exciting thing to have happened to my battery building side business. Beautiful spot welds EVERY TIME!!

[@keithforbes8482]

That said, I do admit that being able to quickly remove and replace cells from a Li-Ion battery system is SUPER convenient!!

[@p_mouse8676]

Use tooth washers to have much better contact (less resistance).

[@MaxGoddur]

Those fuse wires you are attaching are they hard to spot weld? Where did you get those fuse wires? what current can they handle?

[@andrewness2153]

Love the video! But I still prefer the Tesla-style battery packs. After all, they both require soldering anyways. Sometime the old methods are the best. Probably easier for people that aren't as keen into batteries and soldering and what not, but I don't think having someone build a large battery out of 18650s is the best idea for those types of people anyways. In my opinion, a good idea for applications where batteries may go bad often, but those applications are usually high amperage and these battery sleds don't seem up to that task. Keep em coming!!

[@sompka1]

I would try tinning the contact pads with a decent thick layer. The soft metal will make better contact.

[@humanrightsadvocate]

This is a guy you definitely want on your team in a zombie apocalypse.

[@Callummullans]

I came here from motherboard I’m really impressed by this and I am definitely going to be looking into this properly thank you for sharing your knowledge 🙏

[@whatthefunction9140]

this seems very practical and easy to use... its bound to fail

[@guillermomarturetfendt9037]

The system doesnt charge uniformly all batteries. I will fail and explode with time.

[@herbert633]

which is why you use a battery management system which all the 8 pin leads are for, to balance the batteries. this is diy battery packs 101

[@guillermomarturetfendt9037]

Herbert 8 pins yeah... But... For how many batteries? That's the thing, it charges 4 batteries with the same cable. Think a little deeper next time.

[@barranness]

bro, if you were an instructor like at a local college or tech school, i would definitely take your class. your awesome.

[@noncreditgold2661]

Jehu could you tell me were can i buy that pcb? I already have got the rest of the parts here in PR.

[@jehugarcia]

I’ll make it available soon, it just needs final revisions

[@phyrexiacl]

Great idea! The holder are not for strong use contact, but they can fit great in this projects

[@TheViewFromUpHere]

Very clever design. Will you have a link to the PCB files?

[@cottsak]

Love where this is going. Might be the solution which gets me into my first DIY 18650 powerwall. Keep it up.

[@TravisWatson]

Wow Justin's got some PCB design chops eh?!

[@eltirabesitos]

that was a very interesting test. I agree on some of the recommendations, but in my personal experience, these holders work fine with the majority of your projects. I built a 1 KW battery for my diy ebike, and I have been riding it for about 4 months now. I get a speed of up to 30 mph, and depending on how much I use the battery, I have got from 50 miles range with average use and up to 80 miles with low use (more pedaling than electric propulsion). just have to be careful with the bumps on the road that make the connections unstable. If you are careful like I am with that issue, it works just fine. please keep up the good work.

[@volkhen0]

I don't want to be negative but I was testing these holders and at 1A the voltage drop at the connectors to the cell was up to 0,2V... these are not too good for good connection. The cell were not new so maybe that was a factor.

[@Retinalism]

see my comment (29/10/18), you are right Mariusz, friction contacts are unreliable, lack reliable current carrying capacity, and as your test shows, that 0.2V contact drop is the source of the quickly apparent hot spots (@11:30)......

[@haulngrassracing]

Epic! Love seeing all the 18650 holder idea's on here and your Facebook group. Kudos Mr. Garcia

[@stevenc22]

Why not parallel the 7 cells on the holder and then use the solder in fuse connection to select whether that board is position 1, 2,3, 4 ect in the series stack for balancing purposes. Parallel more cells will help with the draw per holder and allow people to make any voltage pack they want.

[@fernandorivera5115]

If you just have 7 cells you can start working any 24v device/inverter with what you have. As you get more cells you just keep adding modules. In a 7p design you have to upgrade in 49 cell increments.

[@stevenc22]

Yeah I understand, this is great for a 24v system.

[@jmonsted]

For a power wall, adding 49 cells at a time doesn't seem like much of an issue. I mean, i've been toying with ways of scaling by 500-1000 at a time as a minimum.

[@cmj20002]

I agree and I don't car for fuse wire, I would use a fuse holder with ATO type fuse that stands out of the side of each. Also you don't need the holders you can use the type that goes on the top and bottom of the cells and use a stud to connect them, that way you don't have to worry about melting plastic.

[@Repair-rookie]

Could you install a spade fuse holder at the front of the pack, would save disassembly to replace.

[@jehugarcia]

Good idea

[@shokovi]

Four to five dollars to connect and house only seven cells is way too much, the assembly is too time-consuming, it provides no thermal management, the common rail that connects all parallel cells is just a breadboard pin that can easily fail and the individual cell fuses are not easily replacable. Why don't we, instead, invest time in designing a simple PCB to fit onto those 4x5 cell holders ?

[@jehugarcia]

Let us know when you finish

[@CoryTaylor904]

Lol

[@jarekf3083]

Those are valid points. This system costs more than batteries, which makes the whole powerpack cost twice. And is also not very efficient (not for EVs like someone said). It could be great for small experiments, but definitely nothing serious.

[@haroldlopez2406]

@@jarekf3083 Very True - the interconnect parts also rely on the (likely steel) riser hardware to carry the load out, which is significantly more resistive than copper. The amount of power wasted in heat on that design makes it worthless for more than 1 or 2 boards. There's tons of profit in those prices as well, so someone is making bank on this junk.

[@horstebreedow8608]

@@jehugarcia what a stupid comment. Why all Mexicans are so afraid of actual discussion.

[@williamwidener4282]

I would like to see your take on cooling. I'm really interested in tab cooling versus submerging the batteries in a die-electic coolant.

[@piripepeno]

bro, fuses are important xD

[@jorgechavez9297]

Just seeing this now lol

[@AlexWilliamson-aw]

Very, very interested in something like this. A use case that I'm thinking of, that I don't see being addressed in the DIY space is something like a high capacity UPS but with the ability to control taking the downstream circuit off-grid, remote battery monitoring, and the ability to control when the batteries are recharged. Specifically, my utility is moving to Time-of-Day billing where the 4-5 hour peak usage costs ~3x off-peak. Therefore even with a sizable efficiency loss, it could be useful to switch certain always-on appliances to off-grid battery during that time, bringing them back on-grid based on battery (reserve for power outage) or off-peak billing, and recharging the battery only in off-peak times, or ideally during excess production of a grid tied solar array. I'd love to see some content in this direction.

I nearly jumped out of my skin when I heard that display power on XD "Nokia? Is that you?" XD

[@jay-rus4437]

Im really wanting to build up a ham radio room that is completely independent from the electrical system in the house. Solar panels, battery bank with 12v supply (13.8v technically), and all necessary monitoring etc. That is my ultimate goal. Ive got a lot to learn

[@fernandorivera5115]

Sign me up for at least 100 modules. This is great for begginers and keeps the fabrication cost/time really low.

[@juanjorx7]

same if we buy them in bulk that will be great.

[@Liquid_Economy]

Great idea!

[@jerry73j]

Where can I buy some modules

[@guillermomarturetfendt9037]

Do not build this!! The system doesnt charge uniformly all batteries! I will fail and explode with time. Trust me, Im an engenieer.

[@fernandorivera5115]

This board is a prototype and will be upgraded in the near future. As for unbalanced charging, thats what the 8 pin plug is for...the balancer. As an engineer you should have written a helpful reply not that "Don't use this" remark. As a fellow engineer I exhort you to do better.

[@magickfighter]

This looks really interesting for some modularity regarding power wall design. I think the heat issue may lie with the clips in the holsters being made of steel ( higher resistance). Im sure if they are made of tinned copper it would perform better. I wonder if any vendors sell holsters with copper contacts?

[@fxm5715]

I suspect the cross section of actual contact area is also an issue. You've got a curved surface touching a flat surface making for a very small cross section of actual contact area that all those angry pixies need to squeeze through.

[@rogerthebarista9732]

Yes, the big problem is the pressure only contact/poor conductor/surface area. Copper can't be used in this way as it is too soft and won't maintain tension.

[@magickfighter]

Roger Thebarista i agree the tension would be a problem if the cells were swapped often enough. For powerwall use, i wouldnt expect cells to be replaced often ( What is the typical replacement frequency?)

[@TheWorcesters]

Interesting and interested. I'll be watching how this goes for you.

[@cschwehr]

This is a great project Jehu! Thanks for sharing and working on this! Building a big wall with 1c draw would give people a huge amount of runtime depending on the config and allow the batteries to last a really long time... Going to be an awesome setup.

[@jehugarcia]

Well 1c is one hour, I think that’s what people don’t get, no one wants to build a house battery that last only one hour, powerwalls need to last 12-24 hours that means the load is going to be 1/12th or 1/24th of a 1c

[@cschwehr]

What I love is using this system, it can easily be expanded... buy ~560 batteries, add ~560 later, and so on. At 48V (what I've considered) you've already halved the amperage anyways. Thanks for all the great work!

[@AaronGoodrich77]

@Jehu, have you considered using thermal grizzly gallium based conductive thermal interface material? I have a feeling that you can better every single set of efficiencies @ connection points and solder points to increase transfer "rate" of electricity to heat ratios. I am no scientist nor claim to be anything more than a guy who figured stuff out by trial and error. (A tinkerer) If you need clarification later feel free to drop questions here below. I would like you to reference how CPU chips are transferring heat when they are overclocked (such as in my ballpark). Then once you realize by sealing the metals together like solder(sp?) does... but not having to do so, you get a drop of 20c by using the thermal grizzly TIM (thermal interface material). So in my case by focusing on the amount of wattage/transfer rate my All in One liquid CPU cooler by Corsair (H105) and by using the right type of fans in the mix. (I use static pressure fans with a focus on the exiting fans to be a "air flow" type fan. (Bias to Corsair and Noctua fans only.) I can control the amount of heat dissipated at the cycle of cooling in the radiator. This enables me to perform faster heat dissipation at the radiator level of the all in one cooler. I read a little on thermal dynamics because of interest. Static pressure around whatever is producing heat also is helpful if it's moved at a proper CFM/Pressure rate. I could see power walls future state including some tech/computer based thinking when designing.

[@totalchaos1976]

gallium=galvanic corrosion check make sure your not going to have a problem . you don't want the metals in the batteries or terminals breaking down. you wont know there's a problem until it blows up in your face .. update 18650 casings is made of aluminum, gallium loves to eat this alloy .

[@CaptainDominic]

Sold out. I wanted to get a couple to test. Could I ge the eagle files to Mill myself?

[@J3sus1sL0rd1]

Maybe you can try out 21700 battery.

[@MaxGoddur]

After reviewing your website and seeing the DIY-power wall thought to myself need to create a PCboard for tidying up the wires in Ebike pack.

[@sorryociffer]

I would like to see a similar system for 38120 batteries!

[@tabelq]

sorryociffer Yes , and 26650.

[@sorryociffer]

Steve Abelquist if it was available in 38120, I'd buy some right now!

[@billunderwood3392]

Is there some dielectric grease or something else quick and dirty that would reduce the resistance at the connection points and lower the temp?

[@asusreviews]

Nice. Don't think those temperatures are anything to worry about. ABS is printed at 230C. So 65C is orders of magnitude lower. I'd be more worried about the circuit board traces and holder resistance. Probably best to hook up a power supply and measure voltage drop across the boards at various currents.

[@TechHole]

65C is not even ONE order of magnitude lower then 230C.

[@asusreviews]

bla bla bla mr technical nit pick.

[@TechHole]

tfw words have meanings

[@asusreviews]

tfw trolls technically nit pick a statement of exaggeration.

[@TechHole]

maybe words with specific, technical meanings shouldn't be co-opted by the general public as "statement(s) of exaggeration"

[@KingOfKYA]

For clarification the battery in the cell between boards need to be balanced, and between the series at least initially. Again per board BMS would make this way better as you could have a high value resistor to eliminate that issue all together. You need thermal sesnors near the contacts (Look at ant charger there will be a ntc under or connected to the contact) also if your going to the effort to make a pcb the bms should probably on the board. Thous silver traces need solder on them For current carrying capacity, and I really hope you paid for 2oz or greater copper with how you assembled it. Thouse pin headers you used an balancing header are rated for 1.25 amp if you buy good ones thouse generic cheapos you bough I would not recommend pushing them past maybe 1/4 of that, And the way you stacked them really is a bad idea so many failure/heat points. I know from experience they don't really mate together that well.

[@me4tgr1ndr]

My favorite part was when he skipped the fuses and burned his house down

[@linearburn8838]

I wonder if you could 3dprint a beefer battery holder with stiffer contact material the heat is probably due to the thin metal in the contact points if you had stiffer contact materal it wouldnt heat as much due to resistance of the thin contact or i wonder if there is a company that could make the battery holders in bulk order with stiffer contact int he right form factor I would imagin in a lot of 100 or so you might be able to get a holder for around 1.50 a unit or so

[@hawkeyes4768]

TBH we need more ideas and faster ways to assemble batteries so anyone can do it and be up and running in just a few hrs

[@Helmut314]

Probably the heat issue is from where the broad metal strips narrows down to pins for soldering. As the current goes up the narrow part with a higher resistance heats up and that in turn heats the strips heat up. Try adding som heavy gauge metal wire in the holders maybe? Its a very interesting idea, seems very easy to build battery packs this way. Interesting to ser where this goes 😀

[@simonkete4809]

probably need a place for thermal couple

[@Robert08010]

It would be interesting to watch the ir camera during charging too. Would this work better with a heat sink separating each battery for instance? One time I installed 2 known to be good working hard drives in a pc case touching one another. But within a few minutes of starting them up, they were over heating because the usual tiny airflow was critical to their operation. Having them touching caused the heat to runaway until they alarmed.

[@wearemilesfromnowhere4630]

ABS plastic is typically good til 150°f. I had the same experience with these cell holders. Kills the efficiency.

[@paulgthawkins]

Ever considered making the schematics open source in order to help kick start a home DIY battery storage?

[@emmseehammer]

I'm confused. Jehu, you inserted all the batteries with positives to the top and negatives the bottom - I would have thought that was paralleling the cells? Is the series-ing done on the PCB traces? To me this looks like a 28P pack. Love the design and implementation and would definitely build my powerwall with these as this design makes it so easy to swap out cells.

[@rogerthebarista9732]

There are no connections within the battery holders, so yes, the series connections are made on the pcb. It's a good idea because you are very unlikely to put a cell in the wrong way...

[@andrewness2153]

^ what he said. It looks like with this particular PCB, the board takes care of the series connections. If it was made in a way where you need to alternate battery orientation in the battery sleds, I could defiantly see myself making a mistake at some point and installing a battery backwards. In my mind, positive up and negative down just clicks, so that's how I would do it. Obviously you can do it any way you want as long as you know what your doing and weld the plans into your brain :)

[@williamreynolds8210]

Thanks Jehu. You said the battery holder and the respective contacts were pulling 18A at 126 deg. and said it should only be 4A. At the end of the video, you said it pulled 4A. I missed something during the experiment. Would you please explain?

[@garystinten9339]

It gets hot here and that seems rather hot. Perhaps a non conductive metal with rails might be a better idea for a rack.. to dissapate heat better.

[@noahhounshel104]

>Non Conductive >Metal You can have one, not both.

[@nic12344]

Gary Stinten If you find a non conductive metal, you will receive a Nobel Prize!

[@BrainSlugs83]

RE: @13:50 -- 130 degrees F is about 55 degrees C. -- ABS plastic (assuming that's ABS) doesn't really start getting soft until at least 160 degrees C (depending on what's mixed in with it). -- If it's Nylon, it can go much higher (like 230+).

[@BrainSlugs83]

www.okwenclosures.com/en/technical_data/enclosures_plastics_guide.html

[@nelsondisalvatore9812]

I think you are up to something brother. 🙂

[@guillermomarturetfendt9037]

Do not build this!! The system doesnt charge uniformly all batteries! I will fail and explode with time. Trust me, Im an engenieer

[@gabesennheiser]

Jehu! I would make the bms trace fuses part of a break out board, and have them mount on the battery side this would help resolve people being stupid, and being to replace a breakout not a entire board and the spacing issues with the bms connectors to help prevent poor installation shorts. you also need to make sure you get proper housing with the batteries, yes the plastic should be abs and can handle 200c without any concern but the batteries shouldn't ever be anything near that hot. my personally preference for fan ventilation would be 140mm fans they are quiet and have good cfm, 120 would do but they are a bit louder. So todo 1. break out bms traces 2. plastic holders from mouser(I dont trust china battery backpacks) rated at the 20-30a continuous of higher end 18650's 3. maybe add a bit of spacing and a fan ventilation mount. Edit: you could also have a specially designed 3d printed battery holder designed completely around battery usage in the case use of power walls allowing custom thickness of posts coming out of the battery holder to help prevent ohm's law making the battery housing heat up, because even if the positive and negative bus bars meet requirements the posts may reduce resistance and create heat. just my two cents from when I used to vape and made custom battery holders.

[@jehugarcia]

These are not powerboards, DIY powerwalls typically load each cell with no more than 500mah, we don’t need to cool cells or extra connectors and ribbons to add expense to the system

[@823Labs]

Looking forward to v2 I'll definitely be interested. As always great vid and great concept.

[@richardcherry664]

Can I make a larger battery pack for a larger toolbox, say 1500 watts or 2000watts? I want to make two or three of these packs to run things in my house if hurricane takes out power grid. Want to connect solar panels to give it continuous energy.

[@jehugarcia]

you can totally do it

[@TheJunkyardgenius]

I also saw wes that tech guy using 38120S cells that have a screw top which means no soldering. He then used busbars and screwed them down. now I can't find an 18650S with screw tops but I had a thought. lf you weld a small nut on the top and bottom of an 18650 then packs can be made the same and just linked together with busbars and a screw. just making the cell with nuts welded on to them is in itself a very sellable product for the ever expanding diy power wall movement.

[@jehugarcia]

Yes I have tried that, but no one wants to glue thousands of little nuts onto cells

[@TheJunkyardgenius]

jehugarcia if you can buy a cell let's say 2 dollars each if you get a good deal and in bulk and sell them for 3 dollars with a nut welded on them or a heat proof glue. I think your onto a winner. perhaps your too busy to do this but anyone can as a start up and make a good business out of it while helping drive forward this revolution.

[@IncredibleSolv]

for ease of swapping the units out I would suggest that you add a optional 90degree pluggable board so that faulty boards wont require total dismantling also heavy current draw, you might have an issue with the current pathways touching the other batteries... it might be advisable to test if you need to put a little more "air gap" between each unit with longer risers

[@ShadwMan]

Is it bad that every time that I watch this video I scream at my computer because Jehu is tapping and scratching the PCB with the metal tweezers?

[@majorredbeard]

No, it's not bad. All I could think during that segment is "You are using tweezers like someone would use their finger, or something more delicate!"

[@shadowgenesis2877]

Not a bad idea. With that setup its quicker once the boards are made, and if you have bad cells, easy replace.

[@garystinten9339]

21700 racks would be nice.

[@MADBONE0]

Gary Stinten I second this!

[@haxto1]

I saw a video that you made or were in that I have been trying to find again but can't locate it. In the vid you were at an outdoor event and talked to a guy who had made an elec bike by mounting a scooter hub motor on the front above his front wheel with the scooter tire pressing against his bike tire. He had it over-volted and it was crazy fast? Can you direct me to that vid please? Thanks

[@AveRage_Joe]

Cool Idea!

[@alienpoker]

AveRage Joe More like a hot idea. Not optimal design. Too much loss at the clips, spot welds are the only decent solution long term. Look at how battery packs for powertools are built. Much fewer cells, yet they spot weld to avoid losses and excess heat. .

[@johnmetric5374]

Jehu, did you notice the closest cells to the discharge get warmer quicker? could you stagger the pin setup so that the current comes from the far side and the near side equally?

[@OffsetFPV]

these pressure fit type contacts aren't safe at all. also if you put these into your car with the vibrations and banging around coud cause issues, wouldn't be worth the trouble, just solder or weld the bloody things.

[@jehugarcia]

These are not for cars, Did you not watch the video?

[@OffsetFPV]

jehugarcia ya I watched the whole video. I believe I saw you digging into you VW and got that idea into my head maybe? thanks for the reply.

[@lowhertzhighspl]

Holy crap! Why did you cut off the resistor itself? (Seen at 05:35) Only using a portion of its one leg. Second question, why was there a single '+' sign on the negative side of the black battery holder next to the circle or 'bubble' (seen at 04:25)

[@TheJunkyardgenius]

Great jehu. its still going to be a bit of soldering. We need something totally idiot proof that just clips together or mechano like and just uses nuts and bolts. extremely simple! A child can put together. those holders, design a new version of them that just snap or bolt together. There is the market for this product.

[@soldermecold7456]

The amount and type of soldering on this job is novice level... I was doing this type of soldering while I was a child. Soldering is easy to learn, cheap to get started, and an excellent skill to have as a DIYer. Personally I enjoy soldering, and the amount on this project is light, fun, and stress free. Give it a try, and don't forget the flux.

[@thenegotiator9701]

Solder Me Cold exactly it doesnt take a lot to learn it

[@experimental_av]

How does the BMS work when the connectors are stacked? Does it show condition of each stack (one cell of each level)?

[@jehugarcia]

It’s all a 7s Xp electrically

[@experimental_av]

cool makes sense. btw is there any good open source firmware or anything for diy powerwall projects? Something that displays the current state, maybe plots usage graph over the day etc.