Let's Solve the Lifepo4 Welded Stud Problem!! Should We Worry About the Small Contact Area?

We have mostly switched over to using welded studs on our Lifepo4 cells to avoid the issue of stripping out the threads in the aluminum terminals. Many are concerned about the small contact area of the welded stud terminals. In this video I try several approaches to address the issue and test the results to prove or disprove the theories. It takes awhile but I feel testing is important. At the end, I conclude with the approach I will take and the priorities I will follow in the final assembly of my battery packs. I hope it helps you to find your path and minimize the pain in getting there.

[@s.hutton2100]

A very Big thank you for all your hard work. You and your wife show much love in the time and effort that you put into making these videos. We all appreciate it. Making our lives happier and our battery building more successful. Cheers from Stephen in Australia.

[@RayBuildsCoolStuff]

Thank you very much for your kind words.

[@Raphael_Hofmann]

You tension everything with the same torque: With the washer, you have less preassure distributed over the contact area, but you have more contact area. Without the washer, you have more preassure distributed over the small contact area.

[@torstenhansen4308]

Just for giggles, and science, you should make a few bus bars with holes that fit the stud and test those against the ones supplied. You have stated elsewhere that expansion/contraction doesn’t worry you and I agree.

[@mikecraig5629]

Hi Ray, Watching through your video a made a few observations. 1) You highlighted an issue with the curvature of the busbars that is probably a result of the stamping process I assume they are using in the manufacture and is easy to straighten as you indicate. In addiction to the curvature of the busbar the flatness of the connection will also be affected by any height difference of the studs and how square the shoulder of the stud is with respect to the busbar. 2) Adding an aluminum washer adds two more contact surfaces for the current to go through at each connection. Also having different materials copper to Al could cause a corrosion problem over time so I would not think this would be a good idea. You could try using copper washers. 3) The current flow is not only between the stud shoulder to the busbar but also between the stud and the nut (across the threads) and then to the top of the busbar. 4) I was unsure about what you were using to measure the resistance but as you were able to detect the difference in resistance you were able to get the required comparisons. I have a 4 wire resistance resistance meter that can measure low resistance values and may do some tests to see what I get. 5) Personally I would drill the holes through the busbar and use a bolt rather than tapping the holes. It will be quicker and easier. 6) I would expect the use of Carbon Paste to be a good idea. 7) One thing that this has highlighted are the benefits of making a good connections. Great work Mike

[@babaluto]

Good considerations here. Thank you. I began using Bellville(spring) washers on top, under the nut. Night and day better than lock washers. They spread the load out and keep the tension or torqure quite well.

[@SkypowerwithKarl]

I’ve been using the same thing. Funny how you can feel washer flatten just before full torque. I did remove the sharp edge on the lower O.D. Just a few degrees from flat so it doesn’t dig into the balance lead lugs.

[@cidcolead1115]

Try inspecting the battery terminals under load with a non-contact thermometer. Lossy connections get hot. There can be lots of reasons they get lossy. Built an electric car in the mid '90's with 16 golfcart batteries. Made lots of mistakes. Drove it for five years and had lots of fun.

[@Leonardkewatchmansnews]

thank you for making this video. it really makes me think of all the bonehead things i have done and how i should approuch my dyi projects but most of all safety is number one! and your video shows us how to be safe or what could happen. thank you for sharing keep the videos coming.

[@brettschacher8644]

Aft5er watching this video, man , I FEEL YOUR FRUSTRATION !

[@jetfu400]

Very informative video. Thank you

[@WarrenAkerman]

Brilliant video. I've read and seen in battery manuals pattery post, busbar, flat washer, springwasher and then nut. The big round washer, spring washer and nut pushes down onto the busbar, which is pushed down onto the battery terminal.

[@raytry69]

If you worry about changing the terminal shape while sanding, then you could use a small wire brush to remove the oxide layer.

[@jimg5998]

Or make a fitting for the Dremel so you could buff it with buffing compound, like final step in tool sharpening.

[@jimmaxwell2259]

Love the testing you are doing. Great work I used aluminium flanged studs(non welded cells) and noalox between the mated surfaces, (after i had cleaned everything with alcohol). I have never rubbed or polished any surfaces, only cleaned. The whole aluminium stud, not just the 'mated surfaces', conducts better, hence the nut on top of the connection, also increases potential conducting contact area. The Flexible tinned 'braided copper' connections means no stress on terminals, less corrosion potential due to dissimilar metals and maximised surface area on the contacts(they can stay perfectly flat when torqued, as no strain on the connections). This is for a RV setup, with lots of movement and vibration to contend with...not sure it would be necessary on a fixed building set up.

[@RayBuildsCoolStuff]

The studs are stainless. So are the nuts. I seriously doubt anyone is using aluminum for the studs and if they are I would warn loudly against buying them. Almost the entire conduction takes place at the mated surfaces. There is no issue with tinned copper mated to aluminum outside a marine environment but I still use an anticorrosion paste. MG847

[@jimmaxwell2259]

@@RayBuildsCoolStuff Yeah, my cells didnt have welded studs, so i felt the dissimilar metals(aluminium cell and stainless steel stud) could lead to corrosion. So why would you warn loudly against putting an aluminium stud into an aluminium cell, when mated up with noalox?

[@RayBuildsCoolStuff]

@@jimmaxwell2259 aluminum isn't strong enough and will break easily. I have had some simple products that had very little force fail for this reason. I'm looking at a headphone stand in front of me that I had to fix for this reason.

[@jimmaxwell2259]

@@RayBuildsCoolStuff oh ok, thanks. They use aluminium studs and nuts on greenhouses here, which need to withstand high winds, so i guess a lot depends on grade and application. Anyways, really enjoying your video's and your methodical approach.

[@Tezza66]

Dude avin floating bus bars in the middle pack makes me wince. It’s just one slip. An molten mettle is flying You will then soon realise what little resistance. There is with. Just a small touch

[@Ivansgarage]

I wonder if antioxidant paste for aluminum wiring would help? I always use it for AC disconnects...

[@lyfandeth]

Sounds like you should be stacking copper crush washers to make the surfaces of the termanil and busbar really conform to each other. Having the busbars lasercut or wsterjet cut from thicker more uniform plate would probaby make a huge difference from the stamped busbars and washers you've got. More expensive, lots less labor.

[@RayBuildsCoolStuff]

The next two videos in this series show how I ended up with a protocol that is very effective, low cost and not labor intensive. Through testing I found what is important and what is not and how to get there with the least effort. I never believe that the answer is to throw money and resources at a construction challenge. Always trying to work smarter not harder even if it takes a few tries to get there.

[@mikedurham4448]

Aluminum Oxide is one of the hardest substances known to man, just softer than diamonds. Zinc is not able to cut or dissolve aluminum oxide either. The aluminum oxide that typically forms on an aluminum connection is only 50-120 angstroms thick. Sanchem's NO-OX-ID penetrates the oxide film by the chemical action of our corrosion inhibitor system.

[@fredhoppe2286]

Thanks for all your passion, and wanting to do it right. I am building an 8s system and enjoy your learnings( or not :). I agree simplicity is the key. Adding extra, complicating, can make varied results. A couple of thoughts while doing this. 1. Cleaning of everything. Sanding the corrosion off the washers, and terminals makes sense, however cleaning of these contact surfaces was not done.. makes me thing there is sand,grit/oxides remaining when you bolt things down. would like to see rubbing used as cleaner prior to bolting down on all contact surfaces( whether carbon paste makes a difference is to be seen still).2. putting an aluminum washer in place to increase the contact surface area would make sense, but increasing the thickness of aluminum between that and the copper bus bar may not be the best idea... actually I thought of perhaps drilling a copper penny as a better washer/conductor.. but then corrosion issue etc.. are issues... LOL... arrrgh... simplicity... keep up the great work. Love your boxes, and design.. Thanks for all you do!

[@RayBuildsCoolStuff]

That is true and something I always do but failed to do it in the video. I watched it and it was a duh moment and has been mentioned by several commenters. This is the problem of one take videos with no editing. Most people edit and hide their mistakes or type script over the video image. I can tell you that I have tested it after cleaning and didn't get a different result. I will guess that is because the paper holds the grit better than the surface but I will get out my borescope and give it a closer look. Thanks for taking time to comment.

[@LibertyDIY]

Turns out pennies are relatively bad conductors due to 95% copper. Surprisingly that makes a huge difference in resistivity.

[@Okkebeltman]

the cells I got has double (non welded studs) which are offcenter so you dont have to worry about puncturing the cell anymore. I quite like it, gives a large flat area for good contact with the busbar

[@leocostantino3184]

You're scaring the death out of me with that lose buss bar on top of those cells. LOL

[@RayBuildsCoolStuff]

Lol

[@sfkenergy]

We do the samething on our packs only above 125AM draw did we see a difference between the washer and buss bar.

[@RayBuildsCoolStuff]

Thanks so much for the data point. I appreciate your watching and commenting.

[@SkypowerwithKarl]

I check mine under lode with a voltmeter probing the terminals just under the bus bars. Looking for the oddball higher voltage.

[@michaelbouckley4455]

1. Yes, you should have been wearing safety goggled or face shield. 2. dont leave bus bars lying on the cells! I have 8x Catl 310Ah cells, the larger capacity seem more likely to get bloated. 4 of my cells were already bloated when supplied as New; and most of the supplied 1mm thin copper bus bars did not fit. I do not like those welded in studs, which look like stainless steel, and have 10mm diameter base, obscuring most of the terminal. Those studs were originally used on lower capacity cells. Eve cells have a 6mm threaded hole, which are better, using set screws. I was advised by supplier not to try to remove the studs. I bought 5x second hand North Star brand longer bus bars, ex lead acid. had to clean them up. Then filed out the slots, for exact fit for each connection, tight against the stud base, onto the terminal proper. The North Star are copper plate at the terminal ends, and flexible flat stranded wire sandwiched between. 2 of the original bus bars fitted, but i tripled them. Having dismantled the battery, recently, i found those to be too short also. I made flexible 35mm2 wire bus bars, (not marine grade, so more flexible and hold shape, better than Digital Mermaids) with 200A crimped lugs having a 10mm diameter hole, required a little filing, fitted onto the terminal. Since then my battery pack has performed better; using for small aircon, overnight, via SNADI low frequency toroidal inverter. I now use less than 20 percent capacity, instead of 30 to 40 percent.

[@davidkettell6236]

if they were bloated they were used cells and you should have complained.

[@highlander2330]

you can also try for the terminals the black hard plastic "sponge" that is used to clean copper pipes before soldering. It cleans the surface but does not make scratches on it

[@BenMitro]

All very interesting. An observation and a thought I can offer on contact resistance; If you torque the nuts down to 6Nm, then you are applying approximately 120lbs of force on the bus bar/terminal over the contact area. The smaller the contact area then, the higher the psi between the aluminium and plated copper bus bar. I imagine a higher pressure will decrease the degradation of the contact resistance over time and I think we all agree greater area will increase the current capacity - if true, there must be a sweet spot for terminal area...the battery people have probably worked this out already given the bus bar and terminal materials. The other thought that occurs is what happens to these connections over time? My guess is that contact resistance will increase with time. With the aluminium washers added, since there is now double the surface area that can corrode, the resistance between the terminals will increase even more from degradation over time. The carbon grease should decrease the rate of degradation I suspect.

[@jeremyallard5449]

Hi Ray thanks for your efforts and the wonderful videographers. What you are doing here makes a lot of sense, especially the adoption of carbon paste in the smaller circuits, I would love to know how well Oxygen Free Copper works, that is if you can get it thick enough as well as tight fitted and elongated hole copper multilayer busbars. Stay safe

[@RayBuildsCoolStuff]

My pleasure!

[@johndaleolsen]

When I put my 4s 280ah pack together - with welded studs - I too assumed the small contact area would be an issue. So I put SS washers on both sides of the bus bars ( top & bottom ) before adding the nuts. After assembly was complete I tested the pack at 30 amps ( charge & load ). I measured the voltage drop between the tops of the studs and noticed around 10mv drop. I removed the washers and ran the test again. No more voltage drop! So my recommendation is to simply use the hardware that the battery supplier provides. In my case the bus bars & nuts were the same as pictured in your video.

[@RayBuildsCoolStuff]

Stainless steel is a very poor conductor.

[@adon8672]

@@RayBuildsCoolStuff I'll not say stainless steel is a very poor conductor but a relatively poor conductor (compared to copper, silver etc). However, like all conductors, if appropriately sized (length, cross sectional area) for the job, it shouldn't be a problem.

[@anothercasualobserver8764]

@31:00 minutes I kicked it into 1.5 speed once I saw you had coffee! 1.25 seems about right for the first half though. ;)

[@machielhoogenes3158]

Ray nicely done, What kind of anderson conector do you use 100amp? Would be nice if they make bigger contacts

[@RayBuildsCoolStuff]

The Anderson connectors that I use are 175 A. I know that they make a 350 amp version as well but I don’t know if they make something larger than that that would be readily available.

[@Doctorbasss]

Your resistacne tester seem to be a model that measire Impedense ( AC at 1kHZ) not DC.. and so the value might be different a bit due to inductance of the busbar circuit. To measure resisatcne i suggest using a simple power supply set to 10A and to cary a current thru your busbar and measure the voltage drop in mV and calculate R=V/I... That way I am getting stable measurement of true DC resistance. I get 0.0325miliohms for my short 52mm long busmars with cross section of 35mm2 for my EVE 105Ah cells. Which is a great value. I then get 0.0397 miliohm measured between the cell tabs under the tightened busbar. That mean the total contact resistance of two tabs to busbar is (0.0397 - 0.0325 ) = 0.0072 miliohms... or 0.0036 miliohms per contact . Doing measurement with proper method and equipement is key! Also since you are usinga 4 wire probe setup that have an orientation, pay attention to which tip of the probe is sensing the voltage and the tip that are carying the current. on close distance measurement, this might affect the value! kzbin.info/www/bejne/eZqViXqlna55rrc

[@alexwoods2836]

👍

[@zilogfan]

Best way to test is just charge the pack as fast as you are willing, or discharge. After say 20 min of high amp input in or out, look at the terminals with a thermal camera and identify any hot spots. This is good for connectors, wiring ect. It is a resistance test with in situ.

[@RayBuildsCoolStuff]

Fastest way maybe, best way? Not a chance. The thing about DIY is that we all get to decide for ourselves what matters and how good is good enough.

[@zilogfan]

@@RayBuildsCoolStuff I appreciate your work and perspective but the difference is the thermal test shows any issue even those you are not directly testing for. It is really the ideal safety and efficiency proof test. No worries if you do not like my opinion though. Great videos...

[@johntalbert8227]

What brand and model of torque wrench are you using?

[@RayBuildsCoolStuff]

I have a few. The small one in this video is relabeled by Nashbar which sells parts and tools for bicycles. I've had it for 10 years. I have another that is more precise that I use for engineering and scuba from CDL. It generally is in agreement with the one from nashbar. I have automotive targeted ones that I've had for about 40 years or more.

[@hamadalthani7535]

Thanks

[@rogerlittlejohn475]

You might check the terminals for full welded contact to the batteries. I received ten out of sixteen where the threaded terminal was contact welded to only one end of the battery. Looked great when received but in the process of removing from package was the flaw discovered.

[@RayBuildsCoolStuff]

all 270 cells I have purchased have had good solid welds.

[@BillWhitcomb]

I have successfully flattened copper pipe to make busbars and have always wondered if the contact with the battery terminals was as good as it should be. Do you think it would be advisable to coat the ends of the busbars which come in contact with the battery with molten lead or solder? I would guess? that the softer material would make better contact at the slight expense of the conductivity loss of the lead while perhaps also lessen any future oxidation of the copper. What do you think?

[@mausball]

One thing you should think about, aluminum will oxidize in the presence of air, unless its protected. Either with dielectric grease (messy) or something like NO-OX-ID (expensive).

[@RayBuildsCoolStuff]

I use MG847. That is what I showed in the video but I didn't call it out by name as I have done in the past.

[@joevasquez1776]

You sanded and then put terminal on? Without cleaning of the sand?

[@brettschacher8644]

Aluminum Oxide has burned down a lot of mobile homes over the years my friend. I think the use of stainless or copper washers with anti oxidation compound might be a better choice in this case. The process of surfacing and cleaning the bases of the bus bar seats is a good idea. Also as I mentioned in the previous post the oxidation inhibitor compound would be a great idea. Sanding can also leave tiny amounts of residue behind. Maybe you considered that already. Washing with Isopropahl alcohol and a little bit of an air blast but nothing with any moisture, use an air drier such as one used in body shops when painting a car. Either way anything and everything that can be done to keep humidity away from the connections is needed as you already have mentioned, Al O2 forms real fast and if the air in the work areas has much humidity to it will make a difference.

[@RayBuildsCoolStuff]

Keep watching. The following videos show my process.

[@jws3925]

Just found your channel. What is the torque setting you use to tighten the nuts on the battery studs?

[@RayBuildsCoolStuff]

Temporary I use 4nm. Permanent I use 5 o 6nm

[@brettschacher8644]

Maybe someone else addressed this already but 2 dissimilar metals such as Aluminum and copper or any other metal will electrolys when electrons flow. No Ox should be used to prevent corrosion as this is part of the NEC when using aluminum wire/cable to make connections in wiring systems. This is definitely a place where a milli ohm meter would a must. Also using Ohms law to figure how much voltage drop/current lose will be present at all the contacts. The smallest amount of resistance in a circuit with rather high currents can generate an amazing amount of heat which will affect copper as when copper is heated on any surface, it actually becomes a copper oxide diode. We don't want or need diodes herer!

[@RayBuildsCoolStuff]

Tin and aluminum in a dry environment isn’t a big problem but I use MG847.

[@roygardiner4002]

How about using stainless ("star") shakeproof washers under the nuts? Their points' penetration should guarantee consistent connections at the same torque. Looks like you have sufficient thread length to use one above and one below the bus bar if necessary.Thanks for your great videos BTW.

[@ralphfoster3088]

if you used a copper cable bus bar, wouldn't it a line better? Lay flatter and have less resistance?

[@stevehopper6068]

Thanks for your hard work. Would be much appreciated if you could put links to your tools and hardware.

[@Davido2369]

Nevermind the glove comments Ray, do your thing! Great project

[@tlanderso07]

Is the resistance load dependent if you measure the resistance on a 4 gauge and a 12 gauge wire you would get the same resistance but based on the amps you need a thicker cable. The washer acts like going from a 12 gauge to a 4 gauge interface.

[@tlanderso07]

Maybe check with an IR gun the temperature difference of the studs while operating to see if the washers make a difference

[@RayBuildsCoolStuff]

Watch further. I don't use the washers. After testing I went a different route. The main takeaway from this video is that testing is better than seemingly good ideas.

[@mikecraig5629]

Hi Ray, Re: My last comment on tapping the busbar holes. I see on one of your other videos you were connecting the wires from the BMS to the busbars and this would be more difficult if using bolts to connect the lugs to the busbars. So I would agree with you to drill and tap the holes for those with the diy skills to tap the holes will be better.

[@RayBuildsCoolStuff]

I have combo drill/taps. It makes it go rather quickly. Including deburring the holes, I averaged less than a minute per busbar for the whole operation. Thanks for watching further. The real point of the video you commented on was that testing is important and often dispels our intuition about how we should do things or what matters. It wasn’t the topic when I started the video. We learned together.

[@brettschacher8644]

The readings you are seeing frequently are in the range normally used in shunt resistors and current limiting stuff. I do a fair amount of electronic circuit construction and use stuff like this a lot. It doesn't take much to mess with you with this kind of stuff. As for the question in the video title the answer is a resounding yes worry much about it! This is the same issue as with sizing wires for the amount of amps needed to transfer from point A to B. Larger wire less resistance, more amps moving with less heat. I'm curious why you mentioned carbon paste because cardon is used as a resistance material in carbon film resistors. I used to do lots of industrial welding where we used carbon arc rods coated with copper to burn out faulty weld joints. Another thing is the difference in hard drawn and annealed copper. If the copper is hard drawn, it won't conform easily to the contact points which can make some difference. I also just looked up a conductivity rating of grades of copper and there is a noticable difference in grades. The fact these are tin plated should have negated the issue. My last comment here will be this. Have you tried copper anti sieze compound? I lied, investigate the differences in compressed as crimped connections verses soldered connections. No difference here with a bolt down connection as to a crimped, obviously there is no way a soldered joint can be done here but the same concept is present.

[@tryagain.k1821]

O.28 mR that is good !. I have Varicore 280Ah with 66mR internal resistance. Some of the 8 cells can only be discharged at 5A or else they drop below 2.5V and the EBC-A20 tester cuts out.

[@RayBuildsCoolStuff]

That’s a real bummer

[@johnlorang2666]

If I ever got cells to hook up I was going to test resistance using Aluminum anticize. Nickle anticize. (used for SS hardware), copper anticize (used for sparkplugs grounding). I also would Artic Silver 5 that is used as a head sink past for computer processers. Silver is a great conductor.. I don't know if you have used any in the past.

[@Hiker97]

Hey Ray, what brand torque wrench do you use

[@RayBuildsCoolStuff]

The little torque wrench is sold for bicycles. I got it from nashbar but if I was buying one specifically, I would find one that handles really low torque values.

[@rogerdekumbis4199]

For the total contact area you have to add the area of the thread. Of course this is nickel plated steel, not copper, but I believe it adds a substantial amount of contact area to the whole setup. -

[@Kyle-wo4vd]

I wonder if you could have glued sand paper to the bottom of a nut and turned the nut back and forth at the point of contact for a more precise removal of the Alum oxide?

[@SnowyOwlPrepper]

Grinding lenses uses laps to form a curve even with infinite radius (flat). Lapping two surface together will get them to mate. Lap the washer to the terminal with a fine grit of emory. Lap the other side of the washer to the buss bar. Use x pattern lapping the buss side of the washer. Use cerium oxide or fine polish for final lap. The tinned copper and zinc nuts factor in the resistance. Love the video and your approach.

[@RayBuildsCoolStuff]

Well folks we have found someone willing to take it further than Ray, way further. 😂

[@davidkettell6236]

@@RayBuildsCoolStuff he needs to get a life. ?

[@Skeptic100100]

I realize this is a year old however, would copper flat washers be a better choice ?

[@RayBuildsCoolStuff]

Watch the whole video. The answer will become clear, and if you use raw copper how will you protect it from oxidation?

[@bwilson948]

The groove in a 3.2 battery busbar is larger than post due to the design of the busbar. The groove provides a larger surface area for the***** battery terminals******** to make contact with, ensuring a more efficient and secure connection. This is important for high-power applications where the battery is subject to high currents and vibrations not the bolt screwed into the battery for securing the bars. You have to allow for heat expansion the chemical reaction is a larger concern of time. A chemical package like 847 - Carbon Conductive Assembly Paste would be a clear winner but are you really building life support equipment to be used on combat ship or plane..We used gold and silver when you had be to near perfect with monthly maintenance.

[@bwilson948]

kzbin.info/www/bejne/l4inZKqFgL-pnbc we can easily go back to the massive batteries, but that would take almost all DIY out of the battery world again. They are way behind with power factoring all non resistive loads still were far more energy is wasted.The military use 440 volts at 400 hz for a reason.

[@jasonbroom7147]

I really like the analytical approach you take to all of this stuff, but when it comes to polishing the contact point on top of the aluminum studs, just take a piece of Scotchbrite pad, twist back n' forth a couple of times and be done with it. That dowel rod you cut is really just making it worse, unless you are painfully careful with how you use it. A longer piece of block material would work far better, but the Scotchbrite will get the job done and not round over the edges enough to worry about. If you really wanted to make a substantial improvement, buy or design a bushing made out of copper with the same upper ID as the slot in the bus bar and a wider base to contact the aluminum stud. That would actually solve your problem, while still allowing for expansion and contraction.

[@RayBuildsCoolStuff]

I've done too much handwork with sandpaper, steel wool and scotchbrite pads to agree with you about the risk of round over. Look at the surface with a 28x magnifier and you will see what you are up against. Removing enough surface to get down to bare metal required some effort and the edges will receive far more pressure if there isn't a solid backing behind the abrasive. The issue of expansion and contraction is often misunderstood. The oval shaped holes in the busbars are not to allow for expansion and contraction. The torque applied to the nuts ensures no movement. They are there to allow for the differences in the manufacture of the cells and the terminal placement. It is different from cell to cell.

[@jasonbroom7147]

@@RayBuildsCoolStuff - I've worked extensively with sandpaper, steel wool and scotchbrite as well. That's like saying I've worked with a sledge-hammer, a ball-peen hammer and a tack hammer. If you can round off the edges of those aluminum contact points, by twisting scotchbrite around the circumference of the threaded stud, then you're actually trying to do so. IF the cells expand and contract, increasing their external dimensions, and the bus-bars do not give, then the welded studs must give. One of the reasons the torque specs are so low, and that flange-nuts are used, is because that mating surface is designed to give under the pressure of an expanding cell. In fact, the very "problem" you're trying to solve has been analyzed by trained engineers, with sophisticated testing equipment...and determined to NOT be a problem. The entire exercise, including the tedious video showing you try to get an "accurate" reading on the resistance between those contacts, is largely pointless.

[@RayBuildsCoolStuff]

@@jasonbroom7147 can you link to the studies you reference? Are you saying these bus bars are designed to give in use? Please link to these studies by trained engineers. That would be valuable.

[@jasonbroom7147]

@@RayBuildsCoolStuff - The batteries, including the connectivity methods, are designed by trained electrical engineers, with testing facilities that far exceed a simple multimeter. The video you posted reflects your advanced attention to detail, but is also done to generate views, first and foremost. This is the classic "solution, desperately in search of a problem". I notice you aren't doing any thermal image testing to determine if this resistance "problem" is actually something to be concerned about. Much to-do about nothing. Hundreds of thousands of perfectly safe and serviceable batteries are being built every year without sanding tiny little washers to create a marginal increase in surface area. IF it was an issue, a copper bushing would be a far better solution than what you're doing. The fact that nobody has solved this "problem" is testimony to the fact that there simply isn't one to solve.

[@RayBuildsCoolStuff]

The discussion forums have many posts where people are concerned about the small contact area of these welded studs. I thought I had found a solution so I tested it and discovered that it didn't make a relevant difference but other things did. Testing is what made me discard my idea for a solution. That's how it works. It is easy to make claims based on our reasoned assessment but without testing that is repeatable it is just another guess by an intelligent person. I really want to read the links to the studies you referenced. I have searched for them. While they may exist, they must be internal to the manufacturer. Can you answer my question about if you think the oval holes in the bus bars are designed to allow movement under use?

[@9111logic]

Having gone through all the procedures of testing all 16 batteries for capacity per your magic videos, (all well above the declared 304ah) looking back at this video I've tested the connection between my flexible bus bar and the contact area for resistance just like you did and found it to be a mere 0.07mΩ. Considering that the terminal itself from side to side measures 0.05 I would be happy with that. However, my question is what happens when a higher current/voltage than the one provided by the 9V battery of the tester goes through the contact? For all my PV wiring I have used a Magger which can shoot 250, 500 and 1000 volts through the cables in order to test for resistance and leakage but I don't feel safe applying such a voltage to the terminal of our batteries even though it would not go through the battery itself.

[@RayBuildsCoolStuff]

When I test this, I am looking for flaws and weak spots. If you wanted to use a thermal imaging camera to look for flaws, then it would be important to use high amperage values. What I am looking for with this little tester is simply relative differences that indicate, a problem to look into further. I have found those problems and fixed them. The other thing that we use it for is the dispel myths. We often think we understand something by intuition, but the data proves us wrong which is what happened in this video.

[@9111logic]

@@RayBuildsCoolStuff Appreciate your comment, Thanks 🙏🥰

[@capt.lennymiller6524]

Okay Ray, why not copper washers? I understand that the graphite grease should conduct electricity but what about dielectric grease?

[@RayBuildsCoolStuff]

Testing proved the washers were not necessary or helpful. The carbon conductive paste prevents corrosion and works very well in testing. What I thought would be best failed to be proven in testing. Testing is my guide. The scientific method should always guide us so we don’t fool ourselves with our own arrogance. I’m right in my assumptions most of the time but definitely not always. That’s why data and testing are so important. What I see happen time and again on the internet is that a smart person will make a false assumption and because it sounds right, it gets repeated by others and without any proof or testing it becomes the accepted paradigm. It happens time and again in every forum and every activity that people take part in.

[@wkrp10splayer19]

how do you know that your tools can accurately and reliably measure tiny voltages?

[@RayBuildsCoolStuff]

One reason is repeatability over hundreds or thousands of measurements.

[@rogerlittlejohn475]

have you checked for galvanic corrosion between aluminum and copper. I would think using a copper washer given better contact being softer than the aluminum?

[@RayBuildsCoolStuff]

Keep watching this and the two videos on the topic that follow. In this video testing proved no need for the washer and that the often raised concern about the size of the terminal is much ado about nothing. Testing is king in my world.

[@MOBiEC1]

Was the original busbar brass and the second one copper?

[@RayBuildsCoolStuff]

One supplier sent brass busbars but the others have always sent copper. I have a video called reduce the risk that talks about the suppliers I’ve used and my experiences with them.

[@MOBiEC1]

@@RayBuildsCoolStuff thanks for your efforts - very informative

[@OwnMyBit]

Um... are the threaded studs not conductive? I'm sure they must be and so there will be a current flow into the bussbsr from them via the nut and any washer arrangement on the top. Or am I wrong?

[@RayBuildsCoolStuff]

The studs are stainless. It isn't a good conductor.

[@OwnMyBit]

@@RayBuildsCoolStuff It is true that stainless has higher resistivity than aluminium but you need to consider the cross sectional area and length of the electrical path in the stud to determine the actual resistance. A M6 stainless stud with an effective electrical length of 2mm (thickness of the busbar it is bridging) has only a RESISTANCE of 69 micro ohms. Thus the value of resistance is very much of the order of the resistances you are measuring and I wouldchave thought your tests and "thought experiments" should take that into account??? Perhaps you could repeat your tests with an insulator over the aluminium area? A paper disk cut out using your punch would suffice. That would determine exactly what effect the connection to the top of the busbar via the stud actually has.

[@RayBuildsCoolStuff]

@@OwnMyBit I’ve tested that many times. Try it.

[@OwnMyBit]

@@RayBuildsCoolStuff That's very interesting. I'd love to see a video testing that because if the resistance is do high I will have to stop my occasional practice of adding a spur connection by just popping a terminal and nut on top of the first nut. I've only worked with lead acid so far so grateful to you for doing the tests and correcting my (faulty) knowledge 👍

[@RayBuildsCoolStuff]

@@OwnMyBit just tested this for you again. With my busbar and terminal cleaned and with paste and torqued to 6nm I measure .20 mohm. When I measure the top of the stainless studs it jumps all around but never measures below .44. I can set it up the way you suggested and test. Let’s see what happens…… ok that was worse than I thought. First the studs aren’t long enough to get full threads on the second nut but I tightened it up with the bottom nut touching the terminals and then the bus bar and then the top nut and measuring from aluminum terminal to aluminum terminal I get a consistent 1.47 mohms so about seven times the resistance.

[@unionse7en]

use studs in the female terminals, once installed the studs need not be rotating while tightening the connection, just tension from the stud. Vs a bolt that is both rotating (friction) & pulling, and it's rotating every time the connection is redone.

[@RayBuildsCoolStuff]

This is good advice for those with female studs in their terminals. I have only used the welded studs.

[@TimHayward]

Would copper crush washers give better results?

[@RayBuildsCoolStuff]

No, I dislike raw copper and if you watch the entire video you see that after testing I abandoned the idea of washers. One of the main reasons for the video is to illustrate how we often follow good sounding ideas without testing and following the results. Later videos show my progression and where I landed.

[@baylanger]

I understand resistance is never good, I'm soon to build a pack so I aim best resistance. My question, if the BMS supports auto-balance, does the resistance matter as much?

[@RayBuildsCoolStuff]

Yes, resistance is a measure of the quality of the connection. The quality of a connection is correlated to its durability. Heat generation is one of the reasons for compromised durability. Energy loss per se is not why I seek good connections.

[@baylanger]

@@RayBuildsCoolStuff Not sure if you followed the thread dielectric-grease-on-cable-lugs-lets-test.74876 on diysolarforum from Dec - It's about testing cable lugs w/ dielectric grease. The link to another thread referenced in the first is a discussion about "putting dielectric grease everywhere". Perhaps you'll want to try such product and test your connections again?

[@kevincarlisle4953]

Hey Ray, if you have enough stud length try running a nut upside down with its flange facing upward to the bottom of the stud then the busbar, and a nut on top torqued down, then check the resistance? This way each busbar will be sandwiched between the flanges of both nuts!

[@RayBuildsCoolStuff]

The stainless steel stud is a very poor conductor. The connection must be to the aluminum terminal and not just the stainless stud.

[@RayBuildsCoolStuff]

Here is a good resource for the conductivity of materials. www.bluesea.com/resources/108/Electrical_Conductivity_of_Materials

[@kevincarlisle4953]

@@RayBuildsCoolStuff Thanks, Ray, I'll check it, how's the weather in your part of the world, its 31 c or 89 degrees here in OZ Downunder, great solar day 37.47Kw?

[@RayBuildsCoolStuff]

Chamber of commerce weather here. 16c low 25c high partly cloudy and that's for the next severn days. We still haven't had a frost. The trees are confused by it.

[@RayBuildsCoolStuff]

just tested this for you again. With my busbar and terminal cleaned and with paste and torqued to 6nm I measure .20 mohm. When I measure the top of the stainless studs it jumps all around but never measures below .44. I can set it up the way you suggested and test. Let’s see what happens…… ok that was worse than I thought. First the studs aren’t long enough to get full threads on the second nut but I tightened it up with the bottom nut touching the terminals and then the bus bar and then the top nut and measuring from aluminum terminal to aluminum terminal I get a consistent 1.47 mohms so about seven times the resistance.

[@abhaykalla210]

I feel the contact of the testing probe with the terminal might contribute more to the measured resiststance then the contacts on the terminal and the bus bar as such.

[@jasondevine6014]

I thought aluminium oxide forms in minutes. I used wd40 on the aluminium as I polished. Would be interested to see a test based on that method. I don't have a low ohms Meter.

[@informationsponge5697]

Ray, have you considered using belleville washers which are slightly cup-shaped and when force-loaded deform as a spring, since they are springs? They perform well in maintaining stack compression within a design load range. I'm also concerned about how casually you combine dissimilar metal conductors in an electrical path. Especially where humidity sometimes becomes high, those dissimilar metal electrically conductive surfaces are micro batteries which cause metal ion transfers.

[@RayBuildsCoolStuff]

I think the teeth on the knurled nuts are effective.

[@RayBuildsCoolStuff]

On the matter of dissimilar metals, Tin copper, busbars, and aluminum terminals are a widely used and typical combination. Both metals are resistant to corrosion, and we see no evidence of problems with this combination in spite of the frequently expressed fears. I tend to be quite conservative in my designs, and yet I have no concern with these connections lasting for decades.

[@RayBuildsCoolStuff]

Consider this, the terminals on the Bsr tended copper. The terminals on the battery are aluminum. The wires in between are copper and our terminated with tinned copper lugs. You’re going to have a very difficult time trying to put the systems together while always avoiding dissimilar metals.

[@brucehillemann9698]

The washers might conduct higher amperages with less loss. i.E. heat. I would use No Ox on the terminals to prevent corrosion over time.

[@RayBuildsCoolStuff]

I hope you will watch the next videos in the series to see how this worked out. The washers didn't help and actually were not needed. I did use a paste to prevent corrosion and aid in the conduction.

[@jamest.5001]

I'd get a brass or copper bolt, drill a m6 hole and tap it, being about 10mm x 30mm, using a M6 grub screw to jam it on the post, then make the bus fit the new post, or what ever bolt you prefer!

[@rickbattle5706]

Polishing is a good idea, however if you don't use oxidation paste the oxide will return. For aluminum transmitting antennas I use oxide inhibiting paste such as Penetrox. However, for dissimilar metals I am not sure of the chemistry. Therefore, polishing alone will only last so long before the resistance goes up.

[@RayBuildsCoolStuff]

I use MG847

[@peter572]

Would flexible busbars solve the uneven surface between battery terminals?

[@RayBuildsCoolStuff]

In my videos you will find that it can be solved at less cost and easily verified by testing.

[@peter572]

@@RayBuildsCoolStuff You have presented an amazing case study, but I think that a slight variation in cell size (due to production or expansion) or mounting surface or excessive vibration (boats, vehicles) may stress battery terminals that are connected by a rigid busbar. Having said, terminal cleaning is beneficial as you have demonstrated.

[@RayBuildsCoolStuff]

⁠@@peter572​​⁠ I will offer this for your consideration. Almost no one who builds these batteries DIY even pays attention to this stuff. I would guess most don’t even use a torque wrench when they tighten down the terminals. You can go on the discussion forums and in the sub forums devoted to problems people have had with their batteries, rigid busbars are not the issue. Almost no premade batteries use flexible bus bars. Many of the bus bars out there that claim to be flexible are not actually flexible to a degree that can compensate for surface variability at the torque specifications we are allowed to observe. These are some of the reasons that I have taken the approach I have. If we simply test the resistance across the connections, we will discover any issue that may need to be addressed.

[@BajanAlan]

Have u tries thin tinned copper washers?

[@RayBuildsCoolStuff]

Have you found any?

[@BajanAlan]

@@RayBuildsCoolStuff I use thick ones to try keep lugs flat!

[@RayBuildsCoolStuff]

Where did you find tinned copper washers? In any case the aluminum washers measured less than .01 mOhms, showed .00 on the tester.

[@hrenes]

copper washers and testing from the top (in the circle of the nut), it has the same potential as the bottom of the terminal.

[@zxrjimmy1]

Any link to exact washers

[@RayBuildsCoolStuff]

In the video I tested the affect of using these washers and came to two conclusions. First, the washers don't consistently improve the connection and second, the size of the terminal doesn't seem to matter to the degree that people think it does and getting the connection right is far more important. The conclusion of the video is that ideas that seem good should be tested and that testing is what guides our best decisions. I followed this video up with two others that tested different methods and settled on a method that is easy and effective. Please watch the follow up videos. They are all in the playlist about making good connections.

[@barriedear5990]

Would a washer with a wider hole that allowed it to sit on the lower level of the terminal not be a better solution? That would give a much larger surface area of contact.

[@RayBuildsCoolStuff]

It has been discussed on the forum and there were even custom sized washers created etc but I think it isn’t good because now you are bearing on the weld which is irregular and probably a less conductive alloy if my testing is accurate. In the next two videos after this one I got to a better solution which also minimizes the effort.

[@barriedear5990]

@@RayBuildsCoolStuff Good enough, will watch it.

[@TK-123]

If it was a copper washer, I would agree. Placing aluminum between two copper points of contact raises the resistance because the inherent reduction in conductivity of the aluminum.

[@RayBuildsCoolStuff]

The cell terminal is aluminum. The washer tested at less than .01mOhm. In the video I came to the conclusion that other factors were more important, the contact area of the cell was not a problem and that we should always test our ideas and our claims using the scientific method to prove or disprove their validity. Often we find through testing that being smart doesn't make us right. We have to test and our results have to be repeatable. The video was a bit tedious and time consuming but testing often is. It did in fact lead me to the conclusions of how I would proceed with my final build which was the subject of the next video from two days ago.

[@TK-123]

@@RayBuildsCoolStuff Well done Ray. !

[@mhkoo1]

Why do you not consider the contact area between the bottom of the nut and the bus bar ?

[@RayBuildsCoolStuff]

The studs and nuts are stainless steel which isn’t a very good conductor of electricity.

[@mhkoo1]

@@RayBuildsCoolStuff I read aluminium conduces electricity 15x better, but with an aluminium nut (which has a large surface contact with the steel stud) one can have a large contact area with the top of the bus bar. Not sure if the aluminium nut performs well in maintaining torque spec... BTW: aren't there any batteries with a better/larger area?

[@bryankronast5179]

Hello Ray and lovely assistant.Carbon is more conductive than copper or brass. Run the paste down the whole buzz bar Can we buy carbon buzz bars.? Thanks for your skills. Kronky

[@PlanePreacher]

What would happen if the washer were placed between the nut and the bus bar?

[@RayBuildsCoolStuff]

It wouldn’t help the connection but it would defeat the teeth on the nut and allow the connection to loosen.

[@PlanePreacher]

@@RayBuildsCoolStuff I was thinking (and did not explain) about more surface area on top giving a larger “pressure area” on the “curved” bus bars. Giving the bus bars a more consistent contact patch with each cell connection on the battery.

[@InimitaPaul]

Forgive the entry level question’s but, would it not be more efficient to insulate the bus bar’s? Also, why not copper? I have access to a lot of raw copper and can make my own if cost is the issue, I was just wondering. Edit: This episode is gold btw. Edit: When you sand down washers etc, blow the aluminium dust off before you use it.

[@RayBuildsCoolStuff]

Hi Paul, I don't understand the context of your questions, sorry. Can you tell me what in the video you are asking about? If you watch the next two videos in the series you will see where I ended up. I evolved the process a bit to simplify and speed it up but also achieved better test results. Thanks for you comment I'm just a bit confused about what you mean about insulating bus bars and why not copper. I'm using tinned copper bus bars. The original batch I received were brass so I had to replace them. There is not reason to insulate them unless you mean in lieu of tinning them. Insulating would be more tedious and less effective. I don't really like seeing the tarnish that forms on copper over time.

[@InimitaPaul]

@@RayBuildsCoolStuff Hi Ray, thank you answering, I got the info I was looking for. Apologies for the confusion, I’m a tad autistic and what sounds like a perfectly reasonable way of structuring a question to me is often not.

[@RayBuildsCoolStuff]

@@InimitaPaul I can relate. Many dear friends on the spectrum. My drive for perfection sometimes makes me wonder.....lol

[@richardknight6508]

Is there a reason you don't use dielectric grease?

[@RayBuildsCoolStuff]

Look at the 45 minute mark. I use MG 847. www.amazon.com/gp/product/B00MG9X3VG/ref=ppx_od_dt_b_asin_title_s00?ie=UTF8&psc=1

[@jetfu400]

Speaking about compression, i have two 48v lifepo4 in parallel with no compression and i see no difference at all. I dont know how compression will help at all so i dont follow that trend. Its been a month since your last upload, where you been sir

[@RayBuildsCoolStuff]

What I do with my batteries is restrain their movement. I don’t care about compressions so much as I do not letting them move when they expand in contract from charge cycles. The reason I do this is because I don’t want that movement to put force into the terminals which can damage the cells. For that same reason I don’t unbolt the restraint until I’ve loosened the terminal nuts. When I build the battery, I restrain the cells movement then I tighten down the terminal nuts. I hope that makes sense. Currently I’m working on our horse trailer that has a living quarters. I’ve transitioned the 12 V house battery to lithium iron phosphate and I’m now in the process of installing a 48 battery with a all-in-one inverter. Hope to have that completed and make a video about it pretty soon. Seems like there’s always things that get in the way though.

[@9111logic]

I would have a slightly different approach to this problem since the stud surface remains the same no matter how much bigger the penny washer is, even though it increases slightly the contact with the bus bar, I would instead take advantage of the stud itself and doubled up on the nuts using them as conductors increasing the area of contact that way perhaps adding a lager washer at the top thus taking full advantage of the bus bar with. Please correct me if I'm wrong 🙂

[@RayBuildsCoolStuff]

The stud is stainless steel which is a very poor conductor of electricity.

[@9111logic]

@@RayBuildsCoolStuff Got it, thanks.

[@9111logic]

@@RayBuildsCoolStuff As I quickly found out by testing, I'm a bonehead 🤦‍♂😆(but I didn't have the tester at the time nor the batteries)

[@Yukonjackman1]

Got a part number for those aluminum washers

[@RayBuildsCoolStuff]

Bolt Depot product number 27373 but I won't be using them. they offered too little benefit after testing and required too much prep work. I ordered 300 of them that I won't be using. I was convinced they would work but that is why I test.

[@ronbethmiller]

What's the torque for these welded cells? Thanx

[@RayBuildsCoolStuff]

I use 4nm for temporary connections and 6nm for permanent connections. The max torque recommendation is said to be 8nm.

[@claesmansson9070]

Two 6 mm studs on each terminal on my new 280 Ah EVE cells, making my own flexible cord bus "bars".

[@Sanwizard1]

Use MG chem silver paste. Works great.

[@RayBuildsCoolStuff]

I'm using MG847

[@barrymayson2492]

Aluminum is about twice as resistancent as copper. So you should really double the area in contact. I used to work on telephone systems the old landline stuff that ran on DC at many amps the old buss bars were copper but that got expensive so they started using aluminum but we had to double the size of the bars to be the same as copper.

[@abelramos8652]

All that don’t mix cooper with aluminum …ain’t supposed cooper got a niquel film to avoid corrosion?

[@intrepidadv8463]

What about using a copper 'crush' washer?

[@RayBuildsCoolStuff]

There are two follow on videos on this topic. You can find them in a playlist about connections. I proved in this video by testing that the washers were not beneficial because the surface area is adequate but there are factors that need to be addressed. Raw copper tarnishes over time so when I was looking for washers I looked for tinned copper washers but was unable to find them and with the excellent connections I now achieve the point is moot.

[@joevasquez1776]

Also polish them clean of sand and oil with micro fiber towel or coffee filter and alcohol

[@diysolaradventures7894]

My brand new cells don't have any holes or studs at all

[@drwhonemo]

that loose bus sitting on the battery freak me out!

[@RayBuildsCoolStuff]

yes but it was in parallel to an existing connection.

[@PatricksDIY]

anyway you can raise the volume in your videos, they are way to low

[@jmaus2k]

No sanding of the buss bars? My bars were speckled with plating that wasn't smooth. Sanding them and terminals helped a lot. Something to be said about lead posts....soft so it forms a good contact and doesn't form a hard oxide layer. Copper lugs and wire is probably better yet. Would flex to get a good contact and have better material for a conductor.

[@RayBuildsCoolStuff]

The carbon paste is supposed to help with the less than perfectly smooth surfaces but testing showed that what matters most is removing the aluminum oxide and ensuring a good mating surface alignment. My 1/0 copper connectors with tinned copper lugs perform no better than the tinned copper bus bars and the thought of making 256 connectors from 1/0 cable is a bit discouraging. 512 perfect crimps coming right up!😩😂😂

[@s.v.gadder1443]

I would like to add, I bought rept cells with "welded" rectangular "studs" and upon assembling them snapped one clean off.... the round one I don't see as an issue but I will never buy the ones with rectangular "studs" again.... j.m.o.

[@offgridtruckerdude7133]

Use red scrubby pads on a slow drill for a second or 2 to clean contacts

[@RayBuildsCoolStuff]

My problem is controlling how much it wears away the edges. Kinda like the first time you use polishing compound on an old car and wear through the paint on the sharp edges and corners. oops!

[@sup3rbird]

The current through the washer still has to come through the small shoulder on the stud so no advantage. A washer and long (connector) nut above the bus bar makes contact all the way up the threaded stud giving a bigger path from the cell.

[@RayBuildsCoolStuff]

Suggest watching the next two videos in the series. Also, the stainless stud is a terrible conductor.

[@tziebe]

What about stainless steel washers wouldn't it be better?

[@RayBuildsCoolStuff]

Stainless steel is a poor conductor.

[@tziebe]

@RayBuildsCoolStuff thanks lerned something again Your Chanel helps a lot im also into building batteries and just got my first batch of 280ah cells