Gen-1 EVE cell terminals causing trouble after bus bar replacement. I should have known better!

This was an unexpected outcome of the simple task of replacing some busbars in the Battery Shelf. I have shown this a few times here on the channel, when the middle shelf battery charges and discharges slower than the top and bottom shelf battery. I always blamed this on the aluminium bus bars we have used for this battery and the resulting higher internal resistance. So, it is not hard to replace these aluminium bus bars with copper ones and lower the internal resistance. But what, if the resistance actually rises afterwards?🤷‍♂️
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[@tubeuser2350]

I had a similar problem with contact resistance between the busbars and terminals. Busbars (presume plated copper?) and bolts all from the supplier of the EVE 105AH cells. Under load, taking millivolt readings between terminal, top of the bolt, and busbar (terminal to bar, terminal to bolt, bolt to bar) concluded that the contact between the terminal and the busbar was where the problem lay. A friend suggested inserting a COPPER washer between the terminal and the under side of the busbar, and that fixed the problem! I think the softer metal of the copper washer helped make better contact. Don't give up on them!

[@OneStepToEscape]

You mustn't use direct connection between two different (electrically) metals like copper and aluminum because of galvanic corrosion. That's why normally, a supplier gives us tin or nickel plated copper busbar for connection of aluminum terminals of cells. So copper washer on the aluminum terminal is not good idea. Weak metal (aluminum) will be damaged by galvanic corrosion

[@tubeuser2350]

@@OneStepToEscape Yeah, thought of that. At the time I put them in, nothing else was working. But, if the battery terminal is aluminum and the busbars are copper (even plated), I haven't really changed anything. I'm using the busbars and screws that came with the cells (from 18650, if I recall). ARE they plated copper, or perhaps stainless steel? How can I tell? Regardless, I'm sure they're not aluminum, so there will always be a dissimilar metal connection. All that said, would putting a thin coating of antioxidant paste on the terminal be proper, or would that just re-introduce the poor contact issue? At least, the battery is indoors, so limited moisture. It's been running for almost a year, with no sign of trouble.

[@mandimandi2523]

Always use Noalox or similar stuff (wago paste 249-130, some mentioned stabilant 22) when using pure copper. I use this stuff even when the copper is nickel-plated ... Clean the contact area with sanding paper and some alcohol (isopropyl alcohol) before installation... And this is also one of the reasons why i use ONLY DOUBLE STUDDED POLES from EVE (original with stainless steel coils). They are a little bit more expensive but the best!

[@EricZuber-z6l]

You beat me to it. It's best to use a several hundred watt load at least. Or an electric heater because it draws a constant current. With a 1KW load any resistance between physical points should be easy to spot. The goal is to get all the contacts to have as little voltage drop as the best one in the group.

[@rdcabal]

Copper is standard for electricity conduction. Silver does 110%, aluminium 70%, steel and coated steel and stainless are grouped at 20%. Copper is also best at heat transfer.

[@Storx-USMC-]

Nice Video, I ran into similar issue with mine, it was over 100mv diff when i first assembled it with the Aluminum bussbars on the batteries with the holes like yours. I ended up chasing it replacing the bussbars with copper water pipe that i smashed flat and copper bolts, but what ultimately helped was i found a copper washer that just barely fit over the top of the terminal, extending the surface area of the terminal and the resistance dropped the most after this change, because more of the connection was touching. I ended up using 3 copper washers on all the terminals, 1 on the terminal to extend the surface area, another that was wider with smaller hole, then the bussbar, then another copper washer for the bolt. I found the copper washers were huge upgrade also due to their ability to crush when tightened to the surface of the connections.

[@rdcabal]

Yep, the beans on busbars are crazy wide.

[@upnorthandpersonal]

I have two packs of those for 6 years now. Like I said before, I've put some MG-847 Carbon Conductive Paste in between and haven't had any issues.

[@TrevorFraserAU]

That's what we use and it definitely helps when under stress (heat, high charge/discharge, etc). Removes the change of there being any tiny air gaps, which as you would probably already know, would mean increased resistance, even if only a very small increase.

[@handwerka-boodfahra-droneflija]

Hello Andy. I measured my 16 cell, LF280K V2, with the same YR1035+ at only 4,37milliohms, but only from the main plus, to the main minus of the battery, except the BMS. Used the original flexible VA busbars and screwed them with 6 Nm. Busbars and terminals cleaned with alcohol. I think that's not so bad. It's my only battery, so i have no chance to make a test with others. Good stuff. We can learn much from you. Greetings from the Saarland, Markus.

[@kevinroberts781]

With all the research you do and all the knowledge you have, I thought you knew better.

[@OffGridGarageAustralia]

Because we are all perfect and never make mistakes.

[@TRS-Tech]

@Off-Grid Garage ... Andy, I think you are spot on not using any of these magic paste products on the terminals. Metal to metal contacts is best but what you should do is clean all contact surfaces with isopropyl alcohol to remove any grease that may be present. Even the natural grease from your fingers can combine and make a difference. Interesting experiment and I feel your frustration, crack a tin and relax 😂 If you really want great bus bars you would be better of buying copper bar stock and making them to fit. Great episode as always Andy 👍

[@krg038]

I enjoyed this video. Great Bat cave. (Battery). I have 10 batteries. My first 280ah was about 6 months before yours. I take 1 battery offline every other month for cell testing. I clean terminals and redo the screw in bolt. I use aluminum bussbars but I've added a copper washer under the busbar. I believe this allowed a flatter connection. Lower mohms. Older Jkbms on all. Only had 1 cell failure on 10 batteries. Newest battery is 3yrs old. 4nm. I keep a spare bms. I still look at every thing daily.😂. Use your heat camera. Sunny So. California no more fires.

[@danielkirk8571]

I have the very same issue on my 12v pack I assembled about 5 years ago. I'm guessing this is why these cells were rejected for automotive use and sold on to us as 'grade a' solar. My delta is even larger and i too get heat on one terminal. Great work as always.

[@markeh1971]

Hi, sorry if someone has covered this before. Copper will build up an oxide layer when even clamped down and give you resistance over time. Not turn green but tarnish. Retorquing the fixing will lower the resistance as the fixing and mating face cut into it. Use a mega tester to do the resistance check. Tin as a coating is the answer, it is soft and seals the faces and makes up for surface imperfections. The fixing also needs to be a coated ones to prevent oxide forming just to be inert, but the path i is mainly through the contact to the mating face not through the fixing it bearing a comparably larger surface area. Tin is an excellent inert material for this use case. Using a torque wrench is also important to make a good clean contact and get the resistances down. Take care M.

[@NaamNatuurlijkniet]

Hi Andy, a few things you could try. Remember the washers from the first seplos case ? You could put washers underneath the busbars to increase the contact area. I did this on my first Seplos case and works flawless. Use new washers. The other thing is that the holes in de busbars have a slightly rounded side and a sharp side, the rounded side should be down for full contact. Last but no least you could first clean the flat terminals without the treads with vinegar, this removes any aluminium oxidation. Finally clean all contact area’s with the right alcohol and mount the bussbars. When worried about difference in terminal level, you could use the orange flex busbars and also replace the 2 aluminium busbars for nickel plated copper. That is the best you can do in this case I think before putting the problem on de cells or the terminals. It takes some work, but would be a great experiment.

[@NaamNatuurlijkniet]

For even less resistance, just for the middle battery, you could get 90’ ringlocks for the cables to the BMS, using slightly thicker cables could also give a small win in getting the resistance of these batteries closer to eachother. I would fix the terminal/busbars first though.

[@NaamNatuurlijkniet]

For even less resistance, just for the middle battery, you could get 90’ ringlocks for the cables to the BMS, using slightly thicker cables could also give a small win in getting the resistance of these batteries closer to eachother. I would fix the terminal/busbars first though. Also the internal resistance of the BMS may be different. Perhaps some fossfets quit working. Compare the internal resistance right on the battery terminals, so without cables and bms in between.

[@markbrettnell3503]

Don't forget though,....you still have 2 aluminum bus bars in the mix. So you really shouldn't have bothered switching the bus bars without doing all of them. Also it makes sense having a higher resistance with the V1 EVE cells. You have bus bars connected through a second free connection of the screw in stud to the terminal. None the less, that's why this testing is necessary! Now we know!

[@BenBrand]

I was thinking the same thing, if there's two bus bars that are slightly different then it might affect the balancing if it's balancing during a high current flow, which it is since he only allows it for a short period of time. The voltage readings on the cells around the aluminum busbars will be slightly different and look slightly higher because of the extra voltage drop and the bus bars added to the voltage in the cell. This could cause an issue with balancing where those cells will be artificially balanced low because he doesn't let it balance for a very long period of time.

[@foeke8740]

If a spot is hot, there are two options. Something else makes it hot, or the resistance is higher than the rest of the system. You can measure the voltages all you want. But it won't change the problem. We have an old CAT mobile phone with a Flir heat camera just for these kind of things. And a resistance meter of course.

[@joulessolar8082]

Andy, I have done the same testing, attempting to determine the cause for the higher differential voltage. My conclution is that the busbars has no impact and the cause is due to the battery cells. The cell batch/production is the source (all cells are not created equal) you will find that over time > 150cycles that the internal impediance/resitance of the individual cells increase +-7%. But not all cells at same rate (from same manufacturered batch). Thus you will find 1-5 cells that will be you lower voltage cells that is causing the > 80mV diff volt. These batteries generaly after 4 years/>150cycles have a reduced capacity of 1-3% (still within specifications).

[@lukasmauerhoff9330]

Hi Andy, as you mentioned in the video, the actual problem is that the surface pressure is too low. In my experience there are minimal height differences between the terminals which, combined with the low torque, causing the busbars to not lying flat on the terminals. In my opinion, the only solution is to use very thin copper busbars. I had a lot of problems with it in the past and now I'm using 1×25 mm copper busbars (very consistent 0.01V voltage drop at 150A). Greetings from Germany.

[@rdcabal]

I like this but terminals have a small contact area. Maybe there should be tight fitted coper JL cross-section 'washers' between studs and busbars and wideo copper washers under the nut. Btw, do you make the bars yourself? How do you drill this, is it laser-cut?

[@lukasmauerhoff9330]

@rdcabal you are right, very small copper washers between terminal and busbar can also help a lot by reducing the surface area.

[@michellekonzack]

Your "greese" is a special contact paste which PREVENT oxidation and also allow you to bolt Aluminium and Copper together. Greetings from Estonia and the Miila Mahe Aed Off-the-Grid Farm

[@jws3925]

Andy, I have three batteries albeit smaller than yours, They are all EVE cells but one of the batteries was put together with the LF version having bolts to secure the buss bars. The other two batteries a couple years "newer" and have the welded studs. The older LF version always seems to have a higher voltage delta when charging-----around 60Mv-----than the other two. I chalked it up to being the oldest battery of the bunch. However, now I have to think it is terminals. Always learning something by watching your videos. Besides, you save me a ton of worry and work trying to figure things like this out. I recall when you ape shit on the terminals sanding and polishing etc. So much work that turned out to be folly. Again, saved us a ton of time not repeating that whole regimen you went thru. Looking back, it is actually funny but at the time you were desperately trying to figure out why some terminal were hot/warm and others not. You would do this or that to the hot one(s), re-torque and test. Then the warm buss bars were on some other cells. It was like you were chasing you tail! Wow, we have come a long way.

[@matthewasanan]

Hi Andy, I suggest switching back to aluminum busbars and also replacing the steel studs with aluminum ones, along with swapping the stainless steel flanged nuts for aluminum. This way, all connections will have the same electrical conductivity, which should definitely help. The current steel studs and stainless steel flanged nuts are hampering the contact area which, at the moment, is not optimal.

[@rdcabal]

Aluminium conducts 3 times better than steel

[@keithj30]

Nice video. You save me so much time and expense by doing all the testing for me. You are a legend thanks Andy. 🤙🤙🤙

[@jussikankinen9409]

Nuclear better and free heat if live near

[@travisarnett9558]

I don't remember a video where you have sanded or cleaned the battery terminals in any way, just the bus bars. I had issues with terminal resistance as well, using the supplied nickel plated copper bus bars that ship with the cells. I done mine like I did installing the bus bars in large industrial motor control centers back in the day. That is using a bronze bristle brush wheel in a drill, 3" (75MM) diameter works really great for me. Brush the bus bar contact area and the battery terminal then immediately coat both surfaces with NO-OX antioxidant, aluminum will form an oxide layer immediately when exposed to air. I suspect that under a microscope you will find all those really fine ridges and valleys left by the brushing action, mesh together really well creating more surface area thus lowering the resistance. With my test setup, I am able to pull 200A continuously from 280Ah cells, from full capacity to totally discharged with NO heat buildup at the terminals according to my thermal imaging thermometer. The temperature increase is spread evenly throughout the entire cell, thus no candles glowing at the terminals. No hot spots, no areas of higher resistance. Hope that helps, good luck my friend.

[@MatWalter-q3h]

Five days ago? This is only 5 days old? I have watched so many of your videos 'when' I watched them is lost... any way... I ordered some cells... the ones that came are not the ones I ordered but as it turns out they are the welded studs with the small contact area so I guess I will be ok... nothing bothers me more than when I want hash and get weed or worse order cells and get a completely different one... Integrity seems to be a thing of the passed... if it ever was. Bless you for being there as the jerk that sent me these clearly could care less.

[@GrahamPearce-ib9om]

Hey, maybe too late now as you have already completed the swap, but a good way of testing for resistance at connections in a circuit is that while the circuit is under load use your volt meter to check for any potential between the two pieces of the connection. In this case, between each battery terminal and bus bar. You then calculate the resistance from the current and voltage.

[@Off-GridManCave-i6t]

Hi Andy from Sunny Phoenix Arizona USA as we all know Heat = Resistance, keep working on your Battery Shelf, 1. Discharge 95 amps and check with thermal imager and voltmeter for voltage drop, I prefer flange nuts only to dig into copper bus bars.

[@OffGridGarageAustralia]

I had nice IR videos of the hotspots and lost them with my new phone. I should have tested this before... Next time👍

[@glencooke494]

Put a M6 copper washer with a small OD under the busbars to increase the force on the connection

[@bigphillAchtung]

This time next week Andy fits 24kt Gold plated pure silver bus bars 🤣

[@rdcabal]

Silver plated copper would do just fine

[@pchris6662]

Another interesting idea Andy, thanks. I’m surprised to see you leave those long Al busbars and not fabricate a copper one yourself. So unlike you to do a job halfway. Sounds like you should replace those with copper flexible busbars that have ROUND holes and not slots so you get improved contact area. Those slots are costing you contact area on cell terminals that don’t have enough to begin with.

[@barrykruyssen]

Thank you for a very informative video. I wonder if putting a thin silver washer between each busbar and the battery terminal would improve anything. I believe, Silver doesn't react with aluminium or copper and silver is 105% conductivity of copper and aluminium is 61% conductivity. Therefore as silver is very soft it would conform to any surface defects between the terminal and busbar. A lot of expense and labour for only a small possible gain. Just a theory.

[@OffGridGarageAustralia]

With anything in between the terminals and busbars you will increase the resistance due to having 2 transitions instead of only 1.

[@petermerle]

I have 5 different lfp banks in parallel and i find the relative current shareing varies depending on soc and voltage. One tends to suck more current at higher voltage but then as overall voltage drops it becomes the weakest. They will all have subtle differences in their charge/discharge curve

[@brendandelear1145]

You should use longer cables when putting batteries in parallel. This is to add a small resistance to all the batteries so the overall resistance between the batteries is a smaller percentage. Ie if you use short cables in your example you have around 10 percent difference but if you use longer cables and have lets say 50 miliohms a deviation of 1 or 2 only 1 to 1/2%.

[@infinitygreenpower]

Dear Andy, You remember I told you before more than one year ago that don't use solid busbar and ONLY use flexible busbars ( all the problems coming from the solid busbars. If you need correct connection between cells use ONLY flexible busbars. Several years ago I was importing cells from China and assembling them using solid busbars that come with the cells and I was facing many problems and after studying and analyzing the problems I discovered that the problem was caused by solid busbars so I started importing flexible busbars and explained this problem to all the Chinese companies I was importing from, and since then most of the Chinese companies started using flexible busbars because of my experience.

[@STRUTZKOFF]

yea but he has the cells spaced . so no thermal expansion loads on the bars

[@infinitygreenpower]

In case of using solid busbars, it will be difficult to make full contact between the cell head and the busbar for most cells because it is not guaranteed that all cells are at the same level and the same flatness and height, so if any tilt occurs, even if it is a fraction of a millimeter, it will lead to failure of the connection between the cell head and the busbar surface,,,, while when using flexible busbars, we will get 100% full contact between the cell head and the busbar even if the cells are not all on the same straight line or their heads are not all at the same level.

[@DominikAndreas]

​@@infinitygreenpowersolid copper busbars are also "flexible" (as copper is quite a soft metal) except for the fact that they don't stretch. Little differences in height or orientation of the stubs will not matter, the solid busbars will deform. You can even deform them with your hand, it doesn't require that much force. So if your cells are uncompressed and spaced as here -> no stretch needed -> solid copper bus bars are fine

[@infinitygreenpower]

@DominikAndreas I did several experiments and discovered that after replacing solid busbars with flexible busbars, the heat disappeared from the heads of some cells. I made several packages and used two types of busbars, and the result was clear in performance. Experience is the best proof.

[@camielkotte]

I ve had some deviation under heavy load and heating of terminals/busbars on my uncompressed 280k with set screw terminals. I flipped them busbars around, cleaned the terminal and put some minimal deoxit on it which I once bought for my vintage guitar amplifier. It solved the heating and deviation on 2 different busbars.

[@SchnickSchnackSchnuck.]

Servus Andy, das war ja eine interessante Erfahrung für mich, da ich die ganze Zeit an eine schwächere Zelle geglaubt habe, die einen höheren Innenwiderstand hat. Nachdem du die Temperatur gefühlt hattest, war es klar für mich. Mein Vorschlag: Messe wie tief der Stehbolzen ins Gewinde geht und wenn er genug Gewindegänge hat, dann schleife doch die Oberfläche bis auf die nächste Ebene herunter, um mehr Auflagefläche zu bekommen.

[@ronhellenbrand]

Made a Flir pictrure during 150A discharge for all mine batteries, to check for hotspots. Torqued the welded studs 8NM several times, some screws needed re-torque after a day to get "bombenfest".

[@Dutch_off_grid_homesteading]

Heya, yes you should have know it wasn't the busbars but the cel's who are not welded you preved that wen you ript out the dreads from the aluminimum contact's. but still a nice video and again proved it is the soort cell's that people use.

[@petryrety]

27:16 *"What are you doing, man? Are you okay?"* 😂😂🤣🤣🤣🤣🤣🤣

[@HouseboatRenovations]

Hi Andy Also check the Flatness of the incoming crimp terminals feeding the bent buss bars. We see many that are "warped" from manufacturing and have reduced contact area and thus get hot. Also if the screw in studs are different alloy than the battery studs you can get galvanic corrosion on the aluminum from dissimilar metals.

[@CollinBaillie]

Dejavu.

[@Nic7320]

Three or more "Ladder connected" batteries with input output cables on opposite corners always pull more current from the end batteries, and less current from the middle batteries. It's not a parallel circuit if you model the milliohms of internal battery resistace AND the milliohms of interconnect resistance. It is a multi-pole RC filter with 3 (or more) stages. PSpice modeling shows the middle batteries ALWAYS lag behind the two outer batteries. The only way to get perfect current balance is with a "star" topology with equal resistance cables.

[@OffGridGarageAustralia]

The studs are made from stainless steel, they don't conduct well. Most current goes through the terminal directly to the bus bars.

[@clarencewiles963]

I feel like after watching this we need to take an exam at the end to get a Degree in Garage Design and Function 😮

[@Juergen_Miessmer]

Hello Andy, im wondering why you didnt checked the resitance of the mounted alluminum bars, by meassuring from bolt to bolt on each bar. You can use your yk1035 wich in real only meassures impedance, or you can run a constant current and use a voltage meter to meassure the drop wich is proportional to the resistance. And you did also not checked the resistance of the BMS and the breaker....

[@saschahorstkotte3331]

Juergen you are right. I measured last year the Millivolts between the bolts and the busbars at a load of 30A on my second build battery. Then I use a Scotch kitchen sponge (the green side) and acetone to clean the busbars. The voltage decrease on more than 50%!!! Since then I use this cleaning method on all meanwhile 10 batteries I´ve build all with copper busbars.

[@forextraderradioman]

@@saschahorstkotte3331 interesting advise ... thank you!

[@maxtorque2277]

It's increbibly easy to "see" problems in busbars, just compare the "sum of cells" in the string the measured battery terminal votlage when high current is flowing, the difference in voltage is the I^2R losses in the buss bars! Most OE BMS do this calc in real time and flag faults based on excessive resistance. Regarding ali bus bars on ali terminals, there are a couple of steps to providing good lowR contact between these. 1) a non-conductive (insulating) alluminium oxide layer forms very quickly over any raw (clean) alluminium. To avoid this, i use a fine emery paper and some light oil, (wd-40 etc) where the oil actually keeps the oxygen in the air away during a gentle sanding of the parts. As quickly as possible i wipe off the bars / terminals post sanding and immediately cover the contact area with a fine layer of alluminium bus bar jointing compound, there are plenty of commercially available compounds that are decent, but all act to keep oxygen out of the interface and prevent the oxide layer forming 2) proper joint clamp load and critially, the provision of suitable spring elements to prevent thermal yeilding & work hardening. There are specific hardward for temrinal bolts which use set crews with intergral spring washers, these make things very easy and safe because the washer is captive to the fastener, massively preventing any shorting accidents during assembly and making it impossible to "forget" the spring washer. However these tend to be available in bulk only (typical 10k min order quantity). So for most hobbiest, you will need to purchase a suitable belville / cone spring washer that suits the clamp load of the fastener size being used, and should aim to torque it to the point where that washer is roughly 66% compressed. This allows the joint to "breath" with changes in temperature (both ambient and dynamic (ie resistive heating)) and to maintain a reasonably constant contact presure. Done properly these two techniques allow the use of alluminium to alluminium high current jointing that stays at a suitably low resistance for a long time, even under significant duress (i have used this technique both for MW level industrial bus bars and for Formula1 eMachines etc!

[@flo3572]

Great videos! You're inspiring Andy ;) I built myself a Yixiang DIY Box V2 with EVE MB31 314Ah with JK-BMS JK-PB2A16S-20P. I see you have a nice flow visualization interface. It would be great to do an Home Assistant video with Victron Multiplus and JK-BMS and your tips for setting up the unit for monitoring. Thanks for your good mood and your good advice. Hi from France

[@teardowndan5364]

I would start removing bars from the front, then you don't have any connected cells to worry about when working on middle and back bars. Starting from the back row makes sense for installing them so you don't have to reach over bars you have already installed.

[@Rui_Caridade]

Andy, following your suggestion of buying from Alibaba as a safe place to do it, I bought for a very good price, I can say amazing price, a Rack mount 16S EVE LF100L Grade A 100Ah cells, very well built box, the only downside is a JBD-16S015 BMS (no Bluetooth and a 60mA balancer and SOC completely out, nothing that a Smart Shunt does not fix). I got it from Shenzhen SMS Energy Technology Co.,Ltd. We are getting good deals from China now as far as I can see.

[@anthonyrstrawbridge]

Excellent work Prost

[@junkerzn7312]

For the version-1 battery terminals, you might be able to improve the contact interface by using a copper compression washer or crush washer. YMMV on that. The thicker ones have the useful property of crushing/distorting under pressure to better-fit contact areas that are not perfectly flat whereas bus-bars (even copper ones) tend to be too stiff to adapt to non-flat terminals. Worth a shot, anyway. Finding a copper washer that matches the contact area of the battery terminal well can be tough, though. (note: this is in addition to the steel washer on top, as the steel washer on top is required to distribute the load of the nut and lock-washer. Nut, lock-washer, steel washer, bus-bar, copper-crush-washer, battery terminal. Like that. YMMV though, it might not work. -Matt

[@jeremyallard7015]

Hi Andy from Sunny Brazil. Try using Carbon Paste on the battery terminals and see if the resistance changes for the better.

[@guywhoknows]

I was watching and could see that it wasn't the bus bars, but hey you recorded this in advance... Sometimes its further away from the problem than we think.

[@kevinz8867]

Andy, why not just plave a small washer on the bottom of the bus bar? do a Belleville serrated washer to dig in and flex. great video! thanks for all my late night beer drinking learning.

[@rilosvideos877]

I use a little oil/grease (just a thin film) to protect the terminals and busbars from any oxidation. There are also special alu oxydation protection liquids available, but i guess its more marketing than actual improvement. One tiny drop on therminal and busbar and wipe it over the surface than fasten the screws!

[@OffGridGarageAustralia]

Tried 3 or 4 of them with good results at the beginning but after a few weeks they became a total nightmare. Best to have nothing in my experience.

[@rilosvideos877]

You should also use a spring ring with the washers to assure a constant pressure on the contact otherwise the material will loosen over time due to material fatigue. Esp. alu will move over time! Also take into account you are measuring also the internal resistance of all cells - so you don't know if the terminals connections are good or cells have increased their internal resistance! You should rather measure voltage drop on the contacts with high current supplied.

[@OffGridGarageAustralia]

Never had a connection that was lose after some time. Even years and all flange nuts are still at 4 Nm like on day 1. That's why we use flange nuts?

[@rilosvideos877]

@@OffGridGarageAustralia What are flange nuts (german?). Maybe thats the trick 😉 A spring ring and normal nut will work as well.

[@OffGridGarageAustralia]

@@rilosvideos877 Same word in German: Flanschmutter 😉

[@rilosvideos877]

@@OffGridGarageAustralia o.k. - da gibts auch noch verschiedene Ausführungen. Solche mit Sperrverzahnung würden evtl. gehen. Ich denke Federring ist dennoch besser weil beständiger Anpressdruck. Solange da nicht viel gerüttelt wird, wird aber auch sonst wohl nicht viel passieren.

[@romanmaring3130]

Measure the voltage between each post +- under load on each bus bar, if you get a voltage then you have some resistance in the connection

[@thomasschmucker14]

I've built about 80 of these batteries using the same busbars as your using there are 2 sides to this busbar and the resistance is smallest when the hole bevel is to the top the round over should be facing upwards

[@mornmorn8425]

It should be possible to put some conductive paste inside theterminals, on the studs. This could help, perhaps some silver ink for PCB repairs.

[@OffGridGarageAustralia]

The studs themselves don't conduct much. They are stainless steel with higher resistance. I would say less than 10%. Most of the current goes directly from the terminal to the busbar.

[@mornmorn8425]

@OffGridGarageAustralia I wonder what's is the difference between welded or screwed terminals? Why the welded perform better?

[@OffGridGarageAustralia]

@@mornmorn8425 It is in the video I linked

[@STEPHENHUTSON-j3q]

thanks for untiring efforts to resolve issues like this - I hope the Chinese manufacturers do not reinstate these older types of terminals in some future production runs. What software are you using to display the voltage and other parameters on your computer screen? I never cease to be amazed at what you are doing in your garage.

[@pipiotrek2375]

welcome back i use aluminium bus bars so far is good greeteings

[@Pho3niX90]

Perhaps, try bolts instead. It will give a more reliable tightening torque vs studs and nuts

[@Shellyfi]

What if.. you put copper washer to between busbar and battery terminal? That could help increase connectivity

[@leonhardtkristensen4093]

Just to put a thought into your problem. I would think that at these low resistance values there might be a problem having different kinds of metals touching each other. It might start to be a little like a battery on it's own or like the connections in a silicon transistor. What I am getting at is that you may run into molecule difference problems. You may get different resistances at different temperatures as well. I would think that if you just overlooked these small differences you would get the full capacity for all the batteries if you where looking at the lot as one battery. I am sure it would be close at least. Also remember that as soon as pure aluminium is exposed to air there will be a layer of aluminium oxide. You never have pure aluminium except in vacuum. It is probably problems like that you can't put zincalume and galvanized roof sheets together or as I have as a problem a galvanized frame on a 1000l tank touching a galvanized tin wall causing rust spots. I think that you are trying to be too perfect. I don't use bus bars. It forces the banks to attempt to be equal which they are not. I just use cables to connect my batteries and let them balance them selves. The losses are minuscule. My goal is a good end result only.

[@GregOnSummit]

Maybe pull a few studs and coat them with some thermal paste. Then torque them down.

[@HybridShedIraq]

Hi Andy, if you want to test deviation, you have to go to 70 percent since they are in high soc charge they will have some deviation. That what I see from my Frankenstein battery. But mines are all welded..

[@junkerzn7312]

I've always assumed that such imbalances would top-out around 10% SOC due to the voltage differentials that develop. But I don't really have solid data for a setup like this. We know the imbalances narrow back to 0% at the top and the bottom, but it would be interesting to see just how bad an imbalance develops through the whole charge or discharge curve. -Matt

[@jameshancock]

Try some copper washers on the studs and then a bus bar. Will recreate their evolution.

[@dcmtrader]

I believe you should isolate the battery from the BMS to test internal resistance of the battery only. No cables, BMS, breakers, etc.

[@petrjiricek8547]

I use 3mm copper flexie busbars only and all cotacts I clean by BGA (buthyglykolacetate) and tight under wet BGA. BGA is ideal chemistry because remove oxides from aluminium, nickel, not it flamable and wapour about one day. Low contact rezistances is very important because local resistances make local heating and if you have only one battery you can not lot of signals about something wrong inside battery. If you contact two batteries in paralel you fast recognise diferences between it.

[@mihailn3082]

As far as I know, any conductor bent over a short distance will increase its resistance and as a result will have energy loss which has the effect of heating it... So you should change those busbars at 90⁰...

[@dirkdaems841]

Maybe try to a washer on each welded terminal which fits over the top contact currently used; Add the washer before adding the busbar this way when the washer is thick enough the force used to fix the busbar will be applied to the second circle of the terminal and also the contact surface will be greater;

[@pcipri76]

Very nicely explained. Thank you once again for the information provided. Could you also post the HomeAssistant dashboard somewhere with this information provided by the 3 battery banks?

[@TrevorFraserAU]

Such boring weather over there, always hot and sunny 🤣

[@OffGridGarageAustralia]

Now, we had rain for two days. Today sun again. getting a good mix of everything.

[@TrevorFraserAU]

@OffGridGarageAustralia well a bit of diversity sounds wonderful 😀 Thanks for all the great work and humour you bring us regularly!

[@danielardelian2]

I think there are two problems here. First, the contact resistance is causing heating of the terminals and efficiency losses. Considering how the BMS leads are connected to the bus bars, a higher terminal-to-busbar contact resistance should cause a HIGHER voltage reading on the BMS for that cell. The terminal-to-busbar contact resistance causes a voltage drop under high current. This adds up with the cell voltage and the BMS would see a higher voltage. But at 25:43 I see cells 12 and 13 have LOWER voltage. So I think the imbalance is due to bad cells.

[@forextraderradioman]

Excellent Video, very informative! ... all the best wishes from Hamburg/Germany, Dietmar, DL4HAO :)

[@taj-ma-haul9094]

and man, it is 80f in Tucson today, it is supposed to be Winter!!! I'm not ready for the free Air Conditioning to leave for 3 seasons yet!!!

[@KeldBroe]

Hi Andy, I wanted to suggest an idea regarding the cell-to-busbar connection: Have you considered placing a washer between the cell and busbar? This modification could increase the contact surface area, potentially improving the current carrying capacity of the connection.

[@robjohnston8632]

It would be interesting to “prove” your theory that it is the terminales by changing out all the cells on shelf 2 to newer cells and use the aluminum bus bars and see how the new cells responds.

[@adrenalineissues]

Is the copper annealed or hard? A quick anneal on the stove will make it soft and able to contact better. The tinning will be trashed but I dont think thats important if you use aluminox or similar.

[@universeisundernoobligatio3283]

Have you measured the voltage across the circuit breakers as they may not all have the same resistance? Check the internal resistance of the BMS? Check your crimps? Maybe also use split lock washers to provide constant pressure and stop nuts from getting loose from thermal cycling. When are you moving your work bench into the air-airconditioned battery room?

[@pulith5220]

You need to check the IR at the plus and minus at battery bcz may be the bms is causing the extra resistance.

[@EitanTsur]

Have you ever played with the Infiray P2 Pro? REALLY nice thermal camera and app; makes for reading the thermal differences between busbars/batteries really easy. I've used it to identify faulty components on PCB's and you can actually see traces heat up and cool down depending on power transfer.

[@OneStepToEscape]

Hello, Andy, thank you. Did you think to try using double basbar (two pcs) for decreasing resistance of busbars? It may improve the situation

[@t3chn0w1z4rd]

Perhaps you need some conductive carbon thermal paste between the bolted connections of the main positive and negative when connecting to the rest of the system (breaker, shunt, BMS, etc)

[@DannyCsaszar]

Another awesome video. Love learning from you. Did you ever upgrade your little 2 post junction connection at the bottom of the battery ?

[@volodymyrzakolodyazhny]

About plato aria of velded vs not velded at 33:50 : surface aria has straight connection with thermal properties (termal contact), but not with electrical contact. Electrical contact resistanse depends on materials and pressure but not surface. In fact, we want to have large contact surfaces for large currents only to make good termal contact (but not for good electrical contact, because the large surface - the lower pressure).

[@volodymyrzakolodyazhny]

It is good t measure internal resistanse at the battery terminals too. If there are questions about it - we may messure half-battery resistance etc (like using binay search).

[@t3chn0w1z4rd]

Needs a washer with an OD that matches the outside of the lower terminal, and an ID of the welded stud, thickness of the head of the welded stud...perhaps nickel coated copper?

[@OffGridGarageAustralia]

Nope, the welded stud terminal work perfect with 230A+ as they are. See the video I linked.

[@halilkacmaz6714]

Thanks Andy, for another amazing video. Just wondering how do you setup the control monitor dashboard in the beginning of the video. how do you determine pool vs heater etc different type of loads also how do you distinguish the DC loads? I assume using different/separate MPPT charger for each DC source; but how do you distinguish the AC loads and is this a feature of victron or not? I just have smart shunt; but planning to buy energy meter and mppt chargers. Thanks in advance for reply.

[@chrisr819]

I am sure the Cells in bank 2 have higher resistance then the other 2, simply aged a Bit differently. The Alu busbars have lower Resistance and it’s Alu to Alu so torqued down no Air gets to it to oxidize and because similar Alu on Contact It’s Not the Terminals. I actually Switch my copper busbar to massive 10mm x 80mm DIN 6082 Alu busbars thats Salt water resistent and that solved all the imbalances. I also glued in the studs with high strength loctide not to Strip the threads.

[@odedeyidamilare]

22:50 you will have higher resistance because of the State of charge.. That is reason the current is lower at when getting full. Resistance should be measured at lower state of charge 30 to 50%

[@brianConover-u2m]

Have you tried moving that one battery to Bank #1 or #3 to see if resistance follows it or replace that one battery completely. It may not be the connections. Temp of battery????? compaired to others.

[@5885ronny]

Danke für deine Videos 👍🤗

[@DanBurgaud]

19:15 I have zero play here; cells in max distance apart for the expansion. And after 2 years, the bloating almost reached the limit. THAT was when I decided to get Yixiang boxes.

[@upnorthandpersonal]

Bloating in normal operation is not normal. Cells should not bloat at all - they expand and contract slightly, but should never bloat. Make sure your charge parameters are correct and you're not operating at high temperatures.

[@DanBurgaud]

@@upnorthandpersonal Last year Andy discovered his cells bloated. After watching that, I inspected mine and decided to get Yixiang boxes and temp controlled AC cabinet. Note: Inverter max charge/discharge current is 90A. JK BMS OTP at 38⁰c (probe tucked between cells)

[@tibuuso]

Hi Andy, what if you use liquid metal used for CPU cooling? Just a thought. Using liquid will make your contact points touch better at microscopic level.

[@benwouda]

Is there a chemistry difference between the 3 packs? Maybe there is a slightly different magic sauce in the middle one..

[@papponmondal]

salute to your effort.... which 2s-24s 15 smart active battery balancer is best to balance battery pack? jk or neey?

[@volodymyrzakolodyazhny]

31:00 It's really hard to get good contact at all terminals untill you use those flexible copper busbars. The 3 mm thick flexible ones are the best. There are 2 mm thick ones too but they are not good for perfection. And they can exist with M3 holes manufactured too.

[@ragohy]

Hi Andy, one of your last words:.."Oxydation" !! Thats the key Word to solve your Problem, since aluminum reacts very fast and you have two surfaces to Care for! Get some "Wago Alu-Plus" paste or similar paste. Btw. your busbars looks very thin, compared to copper bus bars (they should be twice as thick as copper). Greetings from Badisch Sibirien🤓👍

[@elgriego74]

Can't you set these LED colours to match the state of the battery eg charging, bulk, float, discharge etc! So you will know just by looking at the battery's led colour where the state is? I would love this in my system!

[@scsirob]

Interesting video, Andy. Thanks! Just building my first kit, YiXiang v2 with MB31 cells. I noticed in your video that the resistance between cells was reported as ~ 0.16 Ohms. Mine are 0.10 or below. What is an acceptable resistance for the current generation cells with dual screws?

[@ianfotheringham5668]

What are the dimensions of the two bus bars? Did you check the new busbars to ensure they are flat? A milivolt meter check of voltage drop on each bus bar from end to middle will aid diagnosis.

[@ianfotheringham5668]

If the bus bars are cold or cool at high load they do not need to be changed

[@ybeddyj]

Hey Andy, two questions for you 1. Has the seller listed the ibms for sale? 2. Can you post the code to those battery ha cards?

[@OffGridGarageAustralia]

Yes, the iBMS can be purchased here: shop.jamestronics.com/ I'll make a video about the dashboard and show how to build it.

[@errolives8724]

good video, what software are you using to monitor the batteries?

[@ShaneS071]

could you make a detailed video on the setup of the "batmon" add on in home assistant

[@OffGridGarageAustralia]

I have already one on the channel. Does that work for you? kzbin.info/www/bejne/f6KTp6mIYtKEi9U

[@njksky]

Put small washers underneath to get a higher pressure per square millimetre

[@OffGridGarageAustralia]

Nooo, no washer between busbar and terminal. Never!