What's Better? Rigid or Flexible Bus Bars - How to build a 48v Lifepo4 battery (Ep. 21)
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- Опубліковано 27 лип 2024
- In this video, I explore the differences between rigid and flexible bus bars. Using a FLIR camera, I run a ~54A, 10 minute load test, monitoring for heat differences in the two bus bar types.
The root of this video comes from a growing concern I have over vibration and movement in battery packs on vehicles, a boat in my case. Compressing, and to a lesser degree fixing the cells in place will help, but over the span of years it's unreasonable to expect no movement in the pack.
Given this, I worried about the long-term integrity of the bus bar to battery terminal junction. I wanted to see if there would be a noticeable difference if the rigid bus bars that came with the cells were replaced with flexible "bus bars" made from 4 awg marine wire.
Referenced videos;
@WillProwse - "Bloated LiFePO4 Cell Configuration to Reduce Terminal Stress!" - • Bloated LiFePO4 Cell C...
@LithiumSolar - "LiFePO4 Battery Compression, Fixture, and Assembly - What's the Deal?" - • LiFePO4 Battery Compre...
Fire - Note: This was NOT a Lifepo4 fire, I was mis-remembering. - diysolarforum.com/threads/dev...
More relevant article on poor battery connection resistance heating - sinovoltaics.com/learning-cen...
Chapters;
0:00 - Intro, Goals and Theories
2:58 - Test Descriptions
4:10 - Why I'm Not Compressing
5:28 - Making the Flexible Bus Bars / Jumpers
7:38 - A Kitty Interlude
8:50 - Crimper Tip
9:18 - Resistance Testing Flexible Bus Bars
12:05 - Resistance Testing Solid Bus Bars
13:30 - Resistance Test Summary
14:39 - BMS Balance Leads (re)Terminating
17:32 - Test Setup
22:00 - Solid Bus Bar Thermal Test
26:15 - Thermal Test Context (and Giddiness)
27:14 - Setting up for Flexible Test
29:12 - Flexible Bus Bar Test Start
31:25 - A Thermal Kitty Interlude
32:30 - A Winner! (In my opinion)
33:09 - A Request!
The bus bars were made using;
* Ancor Tinned Copper Battery Cable, 4 AWG (19mm²) - www.ancorproducts.com/en/p/11...
* TE Connect 1/4" 4Awg Ring Terminals pn: 8-33469-2 - www.digikey.ca/en/products/de...
* Crimped with a 35mm die, double-crimped to compress the entire barrel - Наука та технологія
IMPORTANT NOTE: shiny metals such as copper, nickel, stainless steel have very low emissivity and high reflectivity in the infra-red range. You CANNOT measure their temperature with IR cameras and IR thermometers. At around 22:45, the hotspots you see are IR reflections of another heat source from the room reflecting from the shiny bus bar. To measure the temperature of shiny metals such as the bus bars, put a small patch of electrical insulating tape on the bus bar, let it reach thermal equilibrium with the metal bar and measure the temperature of the electrical tape patch.
That is clearly visible when the thermal camera moving around 26:47 the "hotspots" also "moving around".
Reflectivity in the infra-red range is a great point that we don't hear enough of. How about a thin cotton cloth that won't melt?
100% Correct! Those are reflective hot spots from another source in the room due to the emissivity of the buss bar. You would also need to configure the camera based on the emissivity of the surface recorded. Even a Flir E75 you have to set the camera to the objects emissivity rate to get an accurate image. However most all reflective or shiny materials have to high of emissivity to capture an IR image but really great at giving you the radiating heat from another source in view of said shiny object.
Yes electrical tape or heatshrink tube (which is not a bad idea anyway). The BMS should monitor the terminal temps anyway. A good one should, anyway.
I have been following your channel for a couple of weeks and greatly enjoy your journey. I too am new to this type of chemistry of battery and GREATLY appreciate your videos and how you are approaching this topic. I also am an IT person and have been in the industry for 30+ years. I'm now a Director but have spent the vast majority of my career as a Systems Administrator so I can relate to all of the hoops you jump through and LOVE that you share some of your insights into your thought process in this endeavor. I hope that my words encourage you to keep making these videos for the folks that aren't experts and can learn a great deal from your knowledge and sometimes "lack" of knowledge. I find it very entertaining and informative! Please keep up the great work!!!
Don’t sell yourself short. I can’t see how Andy or Will could have performed this test any better. The only thing that I would of done is that while you had all the connectors in series for the resistance test, I would have run a heavy load through both sets and compared the voltage drop. In other words, run 100 amps at say 52 volts through each set and measure at both ends to see what the voltage drop across each set had. I’m guessing it would of been a couple of volts lost. This would have given you a second way to measure the resistance, plus measure it under a load. Great video, thanks for taking the time to do all that work and sharing.
Interesting test and completely agree with your thoughts in the intro! There is a lot more to think about in a mobile application vs a static setup on a shelf. Regarding the wire busbar method, I think a lot of it has to do with quality of crimp. I also have to wonder about the additional points where corrosion can occur (under lug crimp) especially in marine applications. Maybe negligible, but this topic is very interesting to think about. I really like the ring terminals you've used as you can see the end of the wire on the ring side.
In the real world, I'll have resin-infused shrink tubing to seal that up. I was thinking of putting some liquid electrical tape / resin / something to seal the end to cover the strands. In this case, I just didn't have enough on hand and it didn't matter for the test. Corrosion is a huge concern on a boat, but that's also why I used tinned copper wires and ring terminals.
You've got access to some decent test gear, I believe. I would very much love to see a higher amperage load placed on the two terminal types to see if there's a more obvious different closer to 1C or higher.
Thanks again for all your videos, they've helped me a lot in the past. :)
@@TheDigitalMermaid Your jumpers are 4awg so they can handle 95-120 amps, with your test pulling 50 amps, I think its 120 amps for that wire given it has 105C rating for the insulation. To pull 280 amps it would need to be 1/0 or 2/0 depending on the insulation spec. I'd be willing to bet that proper built jumpers like you made at a full 1C load would handle the load a lot better than the busbars as I'm suspicious those busbars could actually take the full 1C load without serious over heating. You'd probably have to double them up for such a high load as the seem quite thin, but that gives more chances for bad connections as well.
Tinned wire, tinned ring terminals, proper crimping and sealing them as you list, I can't see how they'd be worse than those flat plate bars especially when as you point out it's a lot easier to get a good mate between the terminal and the rings. Given the fact your connections will be much more solid that would also reduce the risk of corrosion vs the solid busbars.
I think your solution is an excellent one. And since you are limited to 100 amps by the BMS your current wire size is probably perfect.
If you want to measure small resistances correctly, use a micro-ohm meter or put a large, well defined current through the wires and measure the voltage with a standard multimeter.
Thank you so much for making this video. I can appreciate the large amount of time it would've taken you to conduct this experiment. Great video.
Your testing method was brilliant. I would have never thought of chaining them all together like you did to test. That’s why I love watching different peoples videos on s the same subjects. Because you learn.
Enjoyed this video - thanks. I have to agree with a few others who commented about measuring the voltage drop under load. It may help confirm the flexible bus bar advantage you ended up with. I think you're doing really well at sharing what you're doing and the thought process of how you move on to the next step. It reminds me a bit of Andy where he gets curious about something and spends a lot of time and effort to explore an idea. Sharing all this here on YT really demands some thick skin. Lots of critical comments on how others think you should do it, but nothing in the way of technical references to back up the comments.
Thanks a lot for taking the time to conduct these tests. I appreciate your efforts.
You did this justice. First time seeing your videos too...freaking awesome and thorough! LOVE it. I think flexible are definitely better and because they are so short anyways, you wont see a difference. I have to make some now for my packs because I don't want them loosening over time and I have a lot to make due to the fact that I have 3 packs of these in my box truck conversion.
Great video and test. Well done ! I worked on nuclear submarines and call our battery banks used flexible bus bars. We all so used thermal cameras. Same results you got. It was explained to me the solid bars have two faults , one being that they may not make complete connections within the battery post and solid bars are not absolutely solid meaning there not the same density all the way through.
Thank you for sharing your experience. I have similar setup and I found more voltage drop between the battery terminals connected together in case of rigid bus bar than on flexible bus bars. In case of flexible bus bars I was able to fix any contact resistance issues by rotating the connector if tightening of terminal screw at specific torque was not enough. Great video! (sorry for my English).
I JUST went through this same jumper-making process. Thanks for the pro tip on pre-mounting the lugs! Will def be using that.
Hi TDM, you rock! Awesome and very enlighting video about flex or rigid busbars.
Nice to see you use the Victron stuff as well, the Cerbo is my absolute favorite device, next to my MultiplusII 48/5000.
Happy to see not only dudes know their stuff 😀.
My first view of your channel. Wow. Thank you. The results were amazing. Ironically I am a naive amateur but made flexible busbar connectors for my four ready made 135AH LIFEPO4 batteries to put them in parallel so accidentally made a good choice lol.
Your hypothesis that the ring terminal making a consistent flat contact makes sence compared to the rigid busbar potentially not marrying with the terminal as well.
I look forward to looking in your archives now that I have subscribed.
Greetings from South Australia.
So smart to recognize the movement of the terminals changing voltage drop!
The more you use a thermal camera, the easier it is to notice things. The rigid bus bars are reflecting heat from something else. At 26:50 you can see it happen as the hot spots shift to different bus bars. The same thing happens if you look at a window with the thermal camera and then walk in front of it, you will see your thermal reflection in the window just like it was a mirror.
Very true and all you have to do is paint the buss bars and then you will have a more accurate reading, also the flexible buss bars have more mass. I hope this helps. Keep up the good work and stay safe and charged
@@jamesmason7124 There is no need to pain them just put some electric tape on them and you have a quite similar surface to the cable insulation.
Yes I was just going to say that those bus bars were having reflections. I noticed it at about 23 minutes in. There's what looks like it might be a trouble light above the battery and several of the bars seem to be showing reflections of it. Using electrical tape will cause some delay in the readings but a quick and dirty trick would be to make a small template and spray paint something like Ultra flat black paint and an area big enough that you can measure it with your thermal camera on each bus bar. The ultra flat paint has much lower thermal mass and as much thinner and lighter so the response will be much quicker than the electrical tape. Hindsight is 20/20 this would have been really easy to do while you were assembling all those bars together to measure their series resistance...
Lots of good info and tips! Also glad 6nm on the 280ah cell worked for you. for me it stripped out a couple of my cells. It seems for some people it works and others not.
Newbie here..
I like the way of connecting all cables and testing the whole sting to get the total resistance.. I'll take a note of that and used it when the need present itself..
Good video, good cat..
Love your work.
Its eye-opener.
❤️
Excellent analysis. Thank you
Greta job! Am really liking these videos.
I am happy that you have done this test 'for me'. I have a 24v 8 cell pack that was delivered with no bus bars. I was contemplating to go flexible (even if more expensive) because I have the tools to build them
This Lady is one in a million !!!, its refreshing to see her in a predominantly man's world, Her competence is up to par with knowledgeable solar enthusiasists out there ! , keep up the good work ! 👍
I really really hope that more women get into these fields. Hearing someone tell me that I encouraged their daughter to build was one of my highest ever compliments. I really hope we get to a point where kids don't feel that certain interests "aren't for them".
Flexible for me, even with a stationary set-up. I make my own braided bus bars.
@@RJ-cc1fz I compress copper braid into segments of (annealed) copper pipe. Then, I Nickel plate them with a nickel-acetate.
@@upnorthandpersonal i just read through everything on diy solar you posted.. nicely done
@@RJ-cc1fz Thanks!
Awesome video! Thank you for sharing
Thank you for this video. I'd never thought of flexible bus bars. Really makes sense. Sure, takes more time to make them but you're only doing it once per pack. 😊
Happy to! Next video will be an experiment with a new, hopefully more flexible "bus bar".
Excellent idea, better video. I like very much your style. You speak quite quick, but your pronunciation is so good that makes it easy tu understand even for a foreign follower as me. Good job and keep going. Very surprising and glad to see a lady interested in such kind of deep engineering stuff. My very best respects for it!
Thank you, that's quite the compliment! I love the idea of slowly building a wide community, so being accessible to people who have English as a second language makes me happy to hear.
Great research, thanks for the video 🙂
You did a fine job! I’m convinced.
When LithiumSolar video came out, I was thinking the same thing - Use cables for flexibility - duh. Interesting results with the camera. Was not expecting that. Keep the engineering thoughts coming. I really enjoy the thinking parts. Thanks for sharing.
Sharing the process of thinking and figuring things out is a key part of what I want to show. That DIY is problem solving. :)
Well done for starting this conversation, one of the reasons for random heating on solid bars is the makeup of the substrate material..the impurities of the substrates unless you use aircraft grade metals has to be considered. Also one thing to be considered is the refraction of the of the surface material when using thermal cameras, it can trick the camera. I use very expensive thermal cameras in Antartica for research and we also have huge issues with consistent results due to the reflective surfaces, time and thermal soak is the answer here. This is going to be fun to see if anybody picks up on point loading electron transfer.An area to explore is the improvements in thermal transfer for chip design, same principals may also be of interest for connection integrity. happy testing…..
No you did a good test in my opinion an your conclusion is correct, well done an you have saved me some time. Thanks. Michael
Flexible busbars are so much better. For the exact reasons you mentioned in your video. Well done.
I'm very late to the party, but one thing that's different between the rigid vs. flexible bus bars is the flexible ones have insulation on them. That said, you'd expect that the tips might have warmed up. So I think your findings are interesting and valid. Thanks again!
As far as comments about soldering the cables. It isn't needed. Your crimp made a solid connection. You could put on heatshrink with the glue inside. That would seal them really nice.
Great job on testing setup and heat camera. You are showing up Andy and Will for sure!
Thanks for documenting this! Super good test. I think you may be seeing thermal reflections off the rigid busbars. Aluminum has a really low emissivity and especially high reflectance in the infrared regions. You need to turn the busbars into black bodies with some black electrical tape. Then it should be fairly comparable under the thermal camera. I figured out the same thing a few years ago.
Maam, I've been doing electrical work for many years, probably longer than you've been alive. I have formal training in electrical engineering. Use of copper in junctions such as breaker boxes etc has a long long long history. Proper torque, periodic inspection (which includes testing torque/retorque) is necessary to prevent friction issues. Conducting electric doesn't change whether you use batteries or other sources of current. The principals are generally the same. I'd recommend the same procedure as I mentioned above no matter what you are using in electrical junctions. Aluminum is the worse substance to use out of all the common ones being used, presently. Copper is one of the best. Aluminum shrinks due to oxidation in atmosphere and especially without a dielectric treatment. All of this is commonly understood and really doesn't require 'testing'.
Great video. My favorite part is your fur baby. Mine does the same thing.
There is nothing “little” about that cat, adorable yes, little, not so much
Great test, and flir is awesome. Perhaps de-greasing all contact point for future work. Thx for the hard work!
You're very welcome! I thought about degreasing the bus bars, but I didn't see any issues that would justify it in my mind.
@@TheDigitalMermaid my experience is that skin grease etc will corrode metallic surfaces over time. So for longterm stability I always de grease.
Great video....keep it up 👍
Several factors affect the longevity of dissimilar metal compression fittings yet essentially the end product should exhibit a gas tight junction between the crimped parts such that the crimped areas are effectively fused together over the lifetime of the joint. This is controlled by crimping with a known force and thus the sizes of the mated conductor parts. Your approach of standardizing your manufacturing processes, piece parts selection, plating compatibility and tooling is commendable as is your awareness of your supplier parts chain. Note: the electro-potential galvanic difference between mated dissimilar surfaces should be less than 0.25 volt (to minimize corrosion between the dissimilar surfaces in the presence of moisture ).
love your test!!!
Glad I found you!
Wow, what a perfect video especially when my 48 cells are 2 days from being delivered. I'm going to compress the cells with springs and this test helps me to do the right thing and make my own busbars. The whole video is on the longer side but perfectly watchable. Good job and thank you. Anybody out there..., where to get this camera for good money? Regards Pavel
Great video and result. I was not expecting this either. Could be the first ever test here on UA-cam showing the difference. The only concern with the flexible cables are the long term quality of the connection, moisture is your biggest enemy on the boat. More connections could mean more corrosion. Salty water between these different metal connections aluminium, tinned copper, copper, stainless. Are you going to use some sort of anti-oxide paste to prevent this corrosion? I guess you could just use your amazing thermal camera once in a while and check on all these connections, right? Also you will have 6 BMS' which monitor individual cell voltages. Very interesting long term experiment.
Thanks for doing all the testing and science. And showing your adorable cats! 🐱
Stay charged.
I'll be ordering resin-lined shrink tubing (simply didn't have enough on hand for this video), and I'll cap the ends with liquid electrical tape or some other substance that stays gooey to keep air out soon enough. Corrosion is absolutely a nightmare on boats, so it's worth putting lots of thought into.
I've been watching your videos on the JK BMS and have been tempted to order one myself. I'll be really curious to see which I can gather the most data from, exactly for the reason of early detection of connection problems. I may indeed use anti-ox, though I also wonder if I can find aluminium wire and ring terminals... Something to look into. It would be nice to replace the jumpers, terminal posts and nuts all with AL to have only one metal type.
I noticed you showed your pups in the last video!! UA-cam needs more pets. ^_^
Stay SPAT'ed!
@@TheDigitalMermaid What about soldering that void on the end? Much less potential for failure if corrosion in your crimp connection starts setting in. Probably would want to do this after the crimp, but before the heat shrink wrap.
In my boat I like to solder all the connections to avoid electric troubles.
@@ForbiddTV Nice idea, bend them to correct shape BEFORE your solder creeps up to a certain distance and makes them more rigid...
Great comparison!
It's good to see people having ideas and putting them to the test themselves, because there are always so many variables. Andy from OGG had some connection issues with his solid bus bars, so I sent him a set of the ones I had laser cut from 4mm aluminium. That completely solved the connection issues he had, and this has been replicated several times since. So some of the connection issues seem to be related to the material used, and I went for aluminium to match the terminal material.
I make some 12v 280Ah batteries here in Australia, and they all use solid bars. I've found them to be very consistent (because I have them custom made), and that allows a level of certainty I don't get with the OEM ones that can be completely variable size. I've found them to be about half the resistance of a comparable cable with lugs, and that results in about 5w of saved energy loss at a 100A load. So at a 280A load, we would see more like 13w of loss across the bars in a 4S battery. But with cables, it would be about double that.
The solid ones are also of course much simpler and faster, as well as being cheaper. The lack of flexibility in my case isn't an issue, as everything is very tightly packed into the case, so even though these batteries are designed for RV use, there's no notable movement between the cells.
There's also issues to keep in mind regarding dissimilar metals, so the cable version will have a mixture of Aluminium (on the battery terminal), Steel (for the stud and nut), Copper (for the cable and the lug), and often the lug will be Tin Plated. This is something particularly important for marine use. In the setup I use, I've limited it to just Aluminium and Steel.
For testing the resistance, a regular multimeter isn't really accurate enough. You really need a meter specifically designed for testing low impedance. However the regular multimeter might provide a heads up to something being very wrong.
Powerwall Paul, that you? Andy speaks quite highly of your work, if so!
The dissimilar metals concern is very much a real concern over the long haul. I have hopes that the tinned surface will help, but I am very familiar with and worried about copper -> aluminium problems over time. It's the biggest reason I would consider alu bars like yours, just to get similar metals. When you have 4x cells in a packed case, as you build, then I totally don't see the value in flexible bus bars. When you have 16 cells though, it's hard to fix those in place, though. So hence back to my concern for flexible. I wonder if I should try to source aluminium ring terminals and wires...
Though, as @LithiumSolar talked about, maybe a bus bar with a hump to allow for expansion, but made out of aluminium, might not be the top option. If you could find threaded rod that is also aluminium, and perhaps even bolts of the same, it would be wonderful to have a pure aluminium connection setup.
@@TheDigitalMermaid yep that's me :)
One of the other things I do to enhance the stability of the cells, is place a thin 0.3mm sheet of vinyl between each cell. It's just clear vinyl tablecloth available from our hardware store by the meter. It ends up being slightly grippy between the cells, so that prevents movement and/or abrasion. However it wouldn't really make an effect for expansion/contraction.
The bars I make have a slot like most of the solid ones do, so people can space the cells slightly apart if need be, but that would allow more movement again. The bent (humped) bars are a good idea, but from my experience they require a lot of force to bend at all, so I doubt they would be very effective at being a spring of sorts to take up any movement.
For marine setups, I would expect some of the various pastes or greases are going to be enough to reduce the chance of corrosion or electrolysis. But I'm not experienced with those. There's a lot of debate about "conductive grease or paste" too, however they are never as conductive as the metal they're being applied to, so they should be just considered as a barrier to exclude oxygen. Still effective in many cases though.
As always, it's best to try and eliminate items that could cause an issue, instead of apply a fix for the issue.
I'll be following on your journey to see how it all goes. :)
:)@@PowerPaulAu Honoured to have you follow along! There's another channel, Project Brupeg, who I am fortunate to call friends. I mention them because they often speak about corrosion issues (mild-steel components, usually), and the often talk about how sealed compartments, like crash bulkheads, convert the oxygen in the space to rust quickly, then the oxygen is gone and rusting stops. I wonder if covering the terminals with something that blocks gas exchange could help for a similar reason... Whatever oxygen was contain inside is converted and then the metals remain as they are.
Another commenter made a similar suggestion, and I am finding it more interesting as time goes on. I'm going to have to give this some thought. :)
Hahaha, you two here 😊
Firstly, great scientific approach! I've enjoyed watching how you do you testing. At about 22:30 you take out your IR camera to look at the bus bars. You noticed that there was a couple (one in particular) that was showing that it was warmer than the rest. One of the things that notoriously is common about bus bars, whether they are solid or rigid, is the physical connection to the battery posts. If you have a PERFECT bus bar with .01 milliohm (made from 100% Cu, 4mm thick and 12mm wide) you might see an issue IF the "flatness" between the battery terminal surface and the area where the bus bar mates to the battery terminal is not perfect then you will see differences. I'm not sure how to explain this, but it is critical that you get 100% contact with both surfaces.
You can check the "flatness" of the bus bar surface by taking a completely flat surface, like a 4" x 1/8" x 12" flat iron bar (this is just an example. There are lots of things that you can use) and use a 1200 grit emery cloth or sand paper, place it face up on the flat surface, then take your bus bar and GENTLY run the surface back and forth (or in a circular motion) for a few seconds ONLY. Now look at the surface you just "sanded". Are there any markings on the surface which did NOT get sanded? That is the majority of the issues with having the bus bar not making 100% contact with the terminal surface.
There are of course more things to consider... area surface, material composition, etc. The the above is one of the main pain points for making a battery.
NOTE: You can do this test whether the bus bar is a rigid bar or "flexible". The crimp ends need to also be 100% "flat" and make a 100% contact to the battery terminal.
An issue I've also seen is that the battery terminals are sometimes the real culprit! These are made in China with quality control being an afterthought. (Didn't want to add salt to the wound 🙂 )
Nice try, but it is not possible to measure the resistance of the bus-bars with a normal multimeter, even if they are all connected together. The resistance differences are lower than the tolerance of the ohmmeter. 😉
To measure such low resistances you would need to use a milliohmmeter, which normally uses a four wire technique (two wires to supply a constant current and two wires to measure the voltage drop).
Using an IR-camera is a really good idea to find contact or cable resistances by using a higher current. 👍
Good to see, that the flexi bus-bars are even better. Well done and a lot of work.
She will get one for future test. I've sent her the link ;) But the camera test was great and proved the point.
I bought a three pack of two wire kelvin probe clips from Amazon for about $8, and wired them up to a lab power supply and voltmeter. I got readings that looked perfect for the type of wire I was testing - confirmed to be copper, not aluminum. :)
Great experiment! Thanks for sharing.. : )
Great exercise, an very interesting.thank you. Have a great weekend. M
I like your humility but also following Will Prowse I would say your experiment was equally really robust Kudos!
Very interesting thank you. Michael
Great test. Thank you! I'm provisioning my own sailboat with DIY lithium batteries, and your videos have been helpful and thought provoking. I too worry about cell movement in a seaway. I am concerned about chafing of the thin blue plastic insulation around the cells caused by relative cell movement. Long term, when exposed to salt air, there is a risk of the cases developing a chalky, white coating of aluminum oxide - which is as abrasive as sandpaper. The aluminum cell cases have a positive potential, and if two cell cases were ever to come into contact in a series-connected pack, that would cause a short circuit. I'm placing thin sheets of G10 fiberglass between the cells and clamping the whole pack for mechanical stability.
I am also using the same lugs as you, that are open ended on the terminal side. I solder the open ends after crimping and add heat shrink around the cable ends, both for corrosion resistance.
You'll see how I address some of this in more recent videos. In short; 2mm foam padding, and the box has ip67 rated grommets and what not. The trick will be to make the box fairly airtight to minimize salt air incursion.
Will and Andy got nothin on you girl!
Haha! Kind of you to say, but all three of us have very different channels, and I think they compliment each other. :)
WOW I would have expected the rigid to be WAY better! This is awesome content. Also I keep my whiskey in the freezer, no ice needed ;) Thanks for sharing!
I actually prefer the added water, but call me uncouth. :P
@@TheDigitalMermaid ... okay I don't like you any more... jk jk jk :D I tend to not dilute my Seagram's VO but I suspect I have been drinking a lot longer then you ;)
@@TheDigitalMermaid BUT the Glenlivet is treated with upmost care and never chilled. But as a scot that would be sacrilege anyways. :D
@@LadyDewBuild ha ha! We all have moral failings
@@TheDigitalMermaid oh were not getting into moral failings here... UA-cam will ban me for sure!
Just measure the voltage between each terminal post with a wire vs bussbar under load. If you know amps and voltage drop you can calculate resistance and then calculate the maximum current they could run. But "better" doesn't mean lower resistance.....if you don't care about pulling high current. You should just make sure the amount you need to use(and fuse for) is acceptable for the bussbars or cables. An interesting thing is that the cables will be rated for max current when the insulation starts to melt. Bussbars don't have insulation so could be run hotter. And really, you don't really expect to pull high currents for long so either appear to work in your case.
I like your video. Very informative and interesting.
I love your Victron based system. Me too, runs on Victron.
I used to use IR thermometer to monitor my system. But since FLIR is now widely available as built-in camera on rugged phones like Blackview, i am loving these FLIR cameras on phones 😍 they make maintenance work much easier.
Flexible busbars is the way to go. With systems running under 100A, you are unlikely to see much difference or issues with over heating. But on systems constantly running over 100A and even beyond 200A, busbar quality and even the contact surface between busbars and battery terminals become vital.
I have been running 100% full Offgrid solar for the past 2 years. Reliability is everything. And on my system running a 3kw inverter constantly, i see high current above 200A on a daily basis. So i have learnt a few useful tips maintaining my Offgrid solar system.
Most of the potential issues are at the joints and contact points where high current above 200A flows. You want to oversized these. Building just up to spec is not good enough. I used to have 300A busbars, i am now build my v2 build with 1000A busbar with the Victron Lynx.
With battery busbars, i am using very similar cable based flexible busbars as yours with 250A capacity. But in my new v2 build, they would be replaced by 500A flexible copper layer busbars that are custom made.
Although rare, i have learnt from past experience that at high current loads, even hydraulically crimped joints can sometimes fail. It starts off with higher temperatures, then oxide is formed over copper which further increases its resistance and heat generation. Eventually it can become too warm to touch. On a high reliability system, best to use heavy duty Industrial grade busbars that are professionally made.
You can see a 300A version of this busbar here:
ua-cam.com/video/EHqXgcrtOkc/v-deo.html
I noticed there is a slight elevation of temperature on some of your busbars even at the relatively low 53A current. This can happen if the contact surface is not completely flat and /or has oxide formed on the surface. It is worth checking them out to sort out any potential issues beforehand.
Also having pure copper may sound like good idea, but i can tell you from my own experience this is not so. It works great in the first few months before copper oxide is formed on the surface and the busbars tends to heat up and requires maintenance to sand back the surface. Much better is to have quality nickel plated over solid copper. They don't tend to degrade overtime with increased resistance.
In my v2 build, i am deploying 16x 120Ah LFP. Each capable of 280A peak current and 150A sustained output. So just by putting two of these in parallel, it is capable of 300A sustained output. Each LFP has an advanced built-in BMS, so no need to worry about external BMS failures that would screw up my entire battery system. I am keeping my system 13.2v nominal voltage and avoiding series connection, as weak cells can cause long term maintenance problems with mismatched internal resistance. I am putting 16x of these in parallel. Dividing them into 4x battery bank, each bank having 4x LFP in parallel. So it is a bit like a binary tree. The 1000A on Victron Lynx is split into 4x 250A battery banks, and once the battery bank is reached, each battery only have to handle 63A. But i am deploying a 500A flexible busbar here. So plenty of headroom. By having 4x parallel battery banks, i can easily take two offline and the rest of the two can still easily keep up with the max load with plenty of headroom.
You want to over spec your cables by 2x to 3x. Using a 150A cable to run a 50A load keeps your system much cooler with improved efficiency. 😬👍
Also you may want to check out this lifespan of LFP as a function of Depth Of Discharge DOD. It is interesting information to consider. If you only cycle your LFP between 70% to 100% state of charge, they can provide much extended service life providing 70,000 charge cycles.
www.powertechsystems.eu/home/tech-corner/lithium-iron-phosphate-lifepo4/
Thanks for this thorough reply. If you watch videos after this, you'll see I ended up settling on the 4x 10awg sets, which Andy tested a while back. I suspect in my setup, I'll rarely see 50A/pack, so in my case, seeing Andy test this at (I think?) 200A and they stayed cool, barely above ambient, I should be good. :)
@@TheDigitalMermaid Since you are running 48v system with external BMS, you may want to follow Andy on his Offgrid Garage channel as he is running very similar 48v system with many different types of External BMS. He has tons of very informative information and sharing experiences with imbalance voltage in cells and how he tackles this with BMS.
ua-cam.com/video/nPFKkIYFt48/v-deo.html
@@damianhla4940 Andy's been a big help to me and this channel. :)
@@TheDigitalMermaid Excellent! You would find Andy's channel providing a vast range of very practical Offgrid solar information. He is also increasing posting Victron related information on his new Power wall 2.1 build, which is based on the mighty Victron Lynx 1000A system. Having watched his video it inspired me with my v2 build 😅💪💪💪
@@TheDigitalMermaid The only aspect Andy has yet to explore is high current high quality flexible busbars, which i am now in contact with the supplier in China, as i am build my custom 500A flexible busbar system. 😅
His review on busbars actually hinted that the braided flexible busbars from Aliexpress as the #1 performer. I actually tested both, the braided 400A busbar and the layered 300A flexible copper busbars. The latter IMO is the better build. 😅💪
Sorry me again, but I hate to point out the obvious the lug has a round hole suited to the stud and nut for a good connection, but the elongated hole in the busbar is never going to have the same contact area, is always going to be inferior.
As an aircraft engineer with Inspection Authorization (since 1970) I can confirm a properly crimped cable is superior to a rigid link serving as a bus. We use few rigid bus bars on aircraft.
Thanks Rex, that helps me feel better about the hours and hours I spent making the cables. I still worry sometimes that I went overboard with that. :)
Let me solve your number of connections problem.🤔 Bend the solid bus bar into an omega shape with tails making it a spring. Then you get the benefit of both. They would need to be a bit longer though.
Also something not be aware of. Torque isn't a super accurate method of determining clamping pressure. It is just the most convenient. Whether the fasteners are lubricated has a large affect, and whether it is the first or multiple times the connection has been made has a large affect. So when you put the plates on the second time it takes more torque to get the same pressure. Also if you happened to flip some of them, the virgin surfaces will take less torque. So where the wrench is a fixed torque those connections are tighter than the ones with marks from previous tightens.
The point being orient the bars all in the same manner, and possibly use a bit higher torque the next time tightened if the posts can handle the torque. I would imagine the multiple tightenings also changes the resistance by pushing out the oxide layer.
Finally I doubt that resistance reading is accurate. It takes special meters to handle microOhm level measurements. Not sure what you have, but most don't own one. Better than nothing, but not conclusive.
You are completely correct. When is the last time that you have seen a buss bar set up used in a car or a truck battery setup? Think about the multiple battery setups used in semis and heavy equipment and the fact that most if not all use cables instead of bus bars. The vibration is the big problem those applications.
If you are worried about corrosion, just use one of the various greases and/or paints that are available for electrical applications. No-ox is one that I can think of that i have used in aluminum AC applications 100 times without any problems. I imagine that the greases used on automotive terminals would be good for your boat as they would be engineered for high amp DC applications.
As a qualified electrician, one thing that I will be doing is using my favorite connector, the Wago 221. The battery I am building has a Heltec 16-25s 48V 100A BMS, where all 27 leads (25 plus battery negative and positive) are used, so on a 16 cell battery you might have 2 or 3 wires joined at 6 of the terminals, AND also a NEEY Smart Active Balancer. So, I have some 18AWG wire I intend to fly lead from the cell terminal as a single wire, to a suitable 3,4 or 5 way Wago 221, and then bring the BMS and also my separate balancer wires in to. Watching you do this was something I had intended to do, but was unsure about before you did this (kudos to you). Now, I could crimp the 18AWG fly lead AND the 4AWG cable in to the lug, thus reducing connections at the terminal to just one ring connector. Why do this using the Wagos? Simply easier to undo/remove the BMS and Balancer, plus removing the number of connections at the cell terminal. Now to a point you raised about whether the assembled battery would be moved (in a boat or RV) or static (in a home). Whatever use, the terminals WILL have vibrations because wire carrying current will vibrate. In domestic installations, aside from faulty installation/workmanship, the biggest cause of fire is wiring vibrating loose and arcing. Rigid connections are far more prone to this compared to wire to terminal/post connections.
Great videos. I love your presentational style. I found you from Andy's channel.
I just picked up some Wagos. I might end up using them to wire a bunch of 4.4Ah 3.7V LiPo packs together. What have your experiences been like with them?
@@Miskerest They are very good, but do not overload them (current). Stranded wires I would put in bootlace ferrules.
The batteries expand and contract and I have seen about 6 mm gaps form. With your flexible buss bars that wouldn’t matter as much as with rigid buss bars so for me it doesn’t make sense to use rigid. Your experiment showed some bars heating up which I think would get worse over time with the batteries moving every time they go thru the charge discharge cycles. Excellent experiment in my view one no one else has thought to do. Nice work!
the cells should not be able to expand at all. that is exactly the thing you need to prevent as that is caused by gases forming and the cell delaminating over time. a puffy cell is a bad cel.
So, I considered the length of the cable. Assuming you have 280Ah cells, the terminals (allowing for a separation sheet or foam between the cells) is about 75mm, and that you are using 4AWG cable, and allowing for the lugs to be straight. Using the typical minimum bend radius for 4AWG cable, you either have to have a long piece of cable (180mm) which would be a BIG loop, or the distance from the ends of the lugs (where the cable is outside the lug casing) should be about 5mm longer than the actual distance if the cable were completely straight. About 50mm for the cable in this case I think. It might have been better to have three 8AWG cables to make the busbar. The minimum bend radius for 8AWG is the same as the gap you are joining over, so you could make as long as a semi-circle if you wanted (about 70mm of cable between the lugs).
FYI, I recommend the Ancor lugs. Better plating, and closed end to help resist corrosion. The Ancor wire/cable you are using is less flexible, but the best I have found for corrosion resistance. I can hear you now, what does a computer geek living in the desert know about corrosion? Simple, since it regularly above 110 (Fahrenheit), I have been using an evaporative cooler to see if it works well enough to keep things cool. Really impressive how much corrosion can develop in 6 months. Anyway, I suggest you look at spending the extra for the Ancor lugs, and of course high quality heatshrink with glue. The open end on the lugs you are using is an opening for corrosion.
Also FYI, heatshrink ring terminals are worth the extra price, even factoring in the different crimp tool required. I speak from experience, avoid the Ancor brand crimp tool for heatshrink ring terminals.
My infrared camera has lead me to the conclusion that every single time I play with the busbars, I use IPA (isopropyl alcohol) to clean terminals and busbar. I have the 99.5% pure version since my wife is in charge of a Covid test lab, but I am sure a lesser concentration will work fine. Otherwise every time I put them back together I wind up with a high resistance connection somewhere.
Very good test, BTW.
Hiya! I planned originally to have shrink tubing, and I will add it. I just didn't have enough on hand, so I left it out of the video. I always get the resin-lined shrink tubing exactly for corrosion resistance. To be clear, I will never ask "what do they know?" because the answer is always "something I don't". :)
Here is another test for you to do to see how much the aluminum will stretch and compress with heat and cold. First in room temperature trace the outside of the battery buss bar on a piece of paper. Now put the buss bar in the freezer and let it get real cold. Pull it out and quickly outline the bus bar the same as you did at room temperature. Now put the best bar in your oven and heat it to approximately a hundred degrees centigrade. Pull it out and quickly outline the best bar again on the paper. Now with your micrometer or what you have there to measure the distance you can see the actual differences in the temperatures both at the cold side and the warm side of the bus bar. I would be interested in seeing how much stretch it has at the extremes. Good luck
Lou
One thing I enjoyed with my thermal camera was watching cat paw prints on the floor behind a walking cat. They fade in order. It the same principle as seeing someone's PIN at the ATM.
If you live on a boat Used tindwire whenever possible.
Or sautter exposed copper. I like to cut up a pair of jumper cables For a car battery.
You'll notice the wire is micro stranded. Stranded wire works better than solid wire less resistance. Because electricity travels around the outside part of the metal not through the center of the metal so in theory stranded wire has more surface more area to carry the current
I know this is an older video, but I had much the same thoughts when I built mine in 2019. but went for multi-layer copper busbars, with a "kink" in the middle for hopefully all the advantages of bus bar but with the flexibility. Only 24 cells in mine.
However the concern when I researched wasn't the bus bar, but the cell size. bigger cells have bigger "knocks" under big vibrations, so it was suggested for mobile applications that 100-150ah cells were the biggest size. Has more info come out in the year between debunking that. I did semi-compressed mainly to stop them moving about in my truck, which isnt a smooth ride.
However I'm thinking I should check the torque on all my bolts (not checked since mid 2020) now that you have made me think again about what the movement has done in that time.
I'd be really curious to hear if any bolts have backed off. That's some wonderful and valuable real-world data!
Hi Madison, I've got to admire the way you have thrown yourself into this project! I should be getting on with mine, instead of watching yours ;)
For someone who didn't have much experience with electrics, you seem to have quickly built up an incredible collection of tools and instruments. I don't have much to contribute to this. I would only say from electro-technology classes way back, that a stranded cable can carry more current than solid for the same CSA. This was because in AC the current tends to migrate to the outside of the strands, and the solid conductor only has one strand. This is how hollow conductors can save weight. I know of course that this is DC. However when a DC current rapidly changes, the effect might be similar to AC. I also recall that when a (really) heavy current is applied to a cable, the magnetic effect can cause the cable to physically move. Does that matter in your case? Probably not! Watching with interest...
"I should be getting on with mine, instead of watching yours" - Why not both? ^_^
All joking aside, the entire purpose of the channel was to encourage people to start on a project. So yes, go do yours! That's what this is all about.
As for the tools; I have had a long standing policy that, if I am going to try to do something myself, then the money I save can go into decent tools. The logic being that I was going to be struggling enough with my ignorance, I didn't want to make things harder with cheap tools. I can't justify over the top fancy stuff, like expensive bench power supplies, but there is s till a place for "nicer" general tools.
If I can pull off what I am trying to do, then even with the nicer tools, I'm still coming out ahead, cost wise. Best of all, I still have the tools after!
Vidéo utile et bien expliquée. Merci.
Vous êtes les bienvenus!
Well I've helped a woman hold her hair up before but NEVER because she was operating a hydraulic compression tool, LOL. Excellent video, very informative.
When crimping the terminal, it is advisable to cover the wire with hydrophobic lubrication, this will prevent oxidation and increased resistance over time. To prevent the weakening of the tightening of the terminals, you can (you need to) use spring lock washer (DIN 127).
Please give links to "hydrophobic lubrication" and "spring lock washer". I do not know what this is.
Hi, thanks for a great video! May I ask what kind of FLIR camera/tool did you use?
Given that thermal cameras have a hard time properly showing reflective surfaces as false positives, it's a good idea to cover the metallic bus bars with electrical tape to reduce reflection. However, the flexible bus bars are better as you said in vibration/moving environments. This is some Hot Stuff :P lol.
I noticed that in a part of the video I cut. I filmed the quattro and could see my reflection in the big DC plates the wires screwed on to. This camera is just madness on toast.
@@TheDigitalMermaid will you please consider a retest? Repeat FLIR test with tape on Busbars? Frst, I highly recommend "Ray Builds Cool Stuff" YT channel as he addresses busbar lack of uniformity leading to connectivity issues, and flattens them, then cleans with alcohol (acetone is bad for many plastics) and uses carbon based grease to greatly improve results. Lastly his test of 4ga copper crimped connectors was much higher resistance at .25Mohm vs Busbar .17Mohm.
@@jamesbsa6450 Probably not any time soon, I'm afraid. Now that I've made two sets of flexible bus bars, and given how many configuration options they provide (another to be tested in the next video), I don't see myself going back to the solid bus bars.
Merci => Very interesting ! subscriber
Have you done any sort of wire-pullout force testing? I was doing some reading that the junction resistance decreases with increased pull out strength. Until the crimp becomes so tight that the wire pull-out/break strength starts to decrease. But the resistance starts to rise before the break strength starts to decrease.
First time viewing your channel, great video. Not 100% on this but makes logical sense from my understanding of things. I would imagine the difference is a result if the way electrons flow through conductors. The vast majority of flow happens over the conductor surface. If the true cross sectional areas of the copper conductors are the same, then the results make sense because the stranded copper wire has a good deal more surface area than the bars. Now I believe that doesn’t hold true for same gauge solid copper WIRE vs stranded wire. Circular wires bundled together have air voids between the individual strands which is cross sectional area that would be filled with copper in a solid wire. So technically the stranded copper wire would have less cross sectional area, and a slightly lower capacity. You also could have more cross sectional area with the wire vs the bars. You could find that out by cutting the holes off a buse bar making a solid rectangle. Then cut and strip clean a piece of wire that exact length of that rectangle and compare the weight of the two. Assuming their densities are pretty close, that could tell you which one has the larger cross sectional area. Again I haven’t tested this myself so just a my thoughts.
There is a skin effect that results in most of the current flowing at the conductor surface but is to the best of my knowledge only a AC phenomenon that is caused because of the changing magnetic field and induced eddy currents. The skin depth depends on the frequency and the skin is thinner at a higher frequency and is defined as the point the current drops to 1/e ~37%. For 60HZ and copper the skin depth 8.5 mm. So you would see some measurable resistance difference because of this for the used wire dimension.
The problem is that this is a DC battery system and for it the skin depth is infinite. So the surface area is not relevant for a DC system like it would be for a AC system. There will be a minimal effect when the current changes but not when the current is constant.
I might be mistaken and there are some other phenomena but I have not heard about it.
This is an interesting video for me- I just got done making a 18650 pack with a suboptimal spot welder. This "busbar resistance" ended up being a major factor- even in just my discharge tests. "Resistance with current" strikes again. I'm not sure what to use it for now, likely will use it in a low-draw water pump or similar and just wrap the whole thing in kapton and put it in a metal box.
I got some 320Ah LiFePO4 cells in the mail (finally) and used those for my current solar setup instead. Feels much safer, granted they are using solid busbars right now... I might have to pick up some 4AWG wire! They're sitting in a metal toolbox now but I'll have to check out your *non-compressing* battery box build. I like that these flexible bus bars also aren't completely exposed. Much to consider after watching this video!
Solar Solidarity from Maryland.
Sorting all this stuff out is both the joy and frustration of DIY, eh? :)
I am a fully qualified telecommunications technician with 20 years +, who has installed various size 48V battery banks.
Use flexible tinned copper marine power cable, a quality hydraulic lug crimper is a must. Also use white lithium grease on the terminals after connection to stop salt moisture getting in.
re: operating temp difference between the bus bars & cables. ...using FLIR for this gives you a rough idea but the bare metal bus bars have different IR emissivity than the thermoplastic covering the cables used for the jumpers, and thermoplastic also provides some thermal insulation compared to bare metal. So you have multiple factors introducing discrepancies. Best way to test different jumpers (after establishing a baseline ) is to install a few of each type at different places on the same pack and measure the temperatures of the same points are regular intervals with a contact thermometer.
Great video! Totally agree that on any kind of mobile application, flexible is going to be better and safer, although I will definitely echo the thoughts of others here that corrosion will likely be a more significant issue with stranded wire. My boating experience has always been around salt water (Puget Sound and surroundings), and in this area anyway in is always a matter of when, not if, salt will start wicking into the strands and start corroding them. Using good materials will help make that "when" period multiple years.
A question - what was the cross-sectional area of the solid bus bars you used in the test?
Flexible is best you can per bend the cables so they do not push on the terminals and push the cell apart good video
Link to the thermal camera? I'm curious if you moved the warm fixed bus bars to a different location what would happen.
The marine environment - ie salt water minerals - may be an issue with the wire bus-bars if they are not well heat shrinked/sealed. If you go with the cable connectors over rigid bus-bars it would be a good idea to periodically check them for heat build up over years of use to be able to check if there is internal corrosion affecting any individual cable.
Great vid, thanks for posting.
I'm using all marine-grade, tinned copper components. You'll notice I also used boots on the Anderson connectors as well. Keeping moisture out and avoiding corrosion are very much front of mind in the design and build. :)
Hello from the high desert of New Mexico, wow I love your attitude, so humble. You must have a very happy husband. That long cable , I would replace with a thicker one. Also what brand and model of FLIR are you using? Keep up the good work and stay safe and charged
I reckon this bloke is on the money re flexible bus bars
Is "bloke" gender-neutral in Australia? Genuinely curious
@@TheDigitalMermaid What's "gender neutral"?
@@TheDigitalMermaid I'm a 68 year old retired electrical engineer and I'm not familiar with all this new generation language you young whipper snappers have going on and I'm not exactly sure what you're implying? Anyway, thanks for the video mate - very insightful and informative!
@@australiannomad4137 No worries! I thought "mate" was used for guys, but I don't know Australian lingo, so I wondered if you used it when talking to women as well. One of the nice things about the channel is meeting people from other places. :)
Hi,really like how you research things,and inthusiac you are about projects, my question is you once mentioned you wouldn't you wouldn't use a server battery, but didn't explain why cause I was thinking of using a couple of them in a rv solar system, I guess I don't know the difference?
The other option if you want to use solid buss bars, sacrifice a little space between cells to avoid buss bar connection being a flex point. Someone stated elsewhere that they used cupboard door stops on 4 corners to match up at eachother. Center of cell is where they bulge anyways. He used it on B cells then new cells. Provided air space between cells. Just passing on someone elses way around your issues stated
Good test :) You could use some MG Chemicals 846-847 conductive carbon grease on the terminals to make the contact even better. How big is the cable? The busbar is 40mm2 (AWG1).
that stuff is rubbish not conductive scam
Hey, great testing! I wonder if you were to connect your two different bus bars to a load and measure the voltage drop across them while under load if you would see any difference? Either way, enjoyed the video, thanks!
Subscribed!
Welcome, and thanks for joining! Measuring the voltage drop is a great idea, I just didn't know about it back then. I've been learned so damn much! Haha. I suspect I'll be doing more tests once I get the motor installed on the boat. Being able to fire up a proper heavy load will, I hope, make small differences more visible. :)
@@TheDigitalMermaid I'm in Ottawa so if you happen to sail up this way, let me know, I'd love to say hello!
@@SimpleElectronics I'm often in Montreal, I'll see if my sieve brain remembers to take you up on that! :D
Thanks for another great video. You have a new subscriber. I like how thorough you are with explaining everything. I am a beginner like you were and learned a lot from you. Have a nice day.
Welcome! ^_^
To measure low resistance without miliohmmeter: connect a 1A current source across the part (wire, connector, whatever) and a multimeter on millivolts range.
Voltage drop of 1V equals 1 ohm resistance @1A current. It's much easier to measure 10mV than 10mOhm with a standard multimeter.
If you want better resolution up the current to 10A, then each 1ohm will produce 10V
Very interesting and timely test. Thank you. I'm about to build a 12v 280Amp battery and also considering using flexible busbars. I'm considering arranging the cells in a parallel configuration. Then connect the busbars diagonally across rather than a loop. That way it avoids tension on the posts but still allows flexibility.
What do you think.?
I'm going to be playing with layout options that might address this in the next video. Hopefully tomorrow, but possibly middle of next week, work allowing. :)
48v pack is so smart, considering it drops current 400% to a 12v system. The volt drop is our big problem in electric energy!
I just finished shooting a video, will edit it soon, but the wire busbars will perform equally as well as the rigid. I have a BH 100ah pack that I removed 16" (yes 16 inches) of wire between cells, and directly soldered the tabs. Made no difference in usable capacity, the losses are negligible.
I would use the flexible links even in a static install. No matter how stable you think your install it is, there's always going to be some vibration or movement. The heavier and stiffer the stuff inside of it is the higher the resulting strains will be. Let's assume that your battery case is infinitely stiff and strong. Soil expands and contracts, heaves and subsides. Your perfect battery pack isn't going to transmit any torsion, flexion, tension or compression, but it's still going to tilt as the ground changes its level, changing the direction of the force of gravity. Even far away from man and machine, the ground never truly stops shaking, shaking your battery pack and everything inside it. Then there's acoustic energy. Thunder, aircraft, nearby machinery, sound systems, animals, wind and wind blown debris and precipitation. Even if your install somehow it's somewhere where none of these apply you're still going to have thermal expansion and contraction to deal with - Unless you never charge a discharge your battery back - LoL
Oh, flexible is the way to go. Add what you said, and consider I'm installing these in a boat... Motion and vibration will be constant.
my battery is a p2s16, i've used flexible busbars in between the serial cells. the pack is running my house, max charge is 100amps, max discharge is around 95 amps, pack has been running for 4 months now and the cells are still ballanced enough to charge up to 3.6 volts without problems.
One thought, the solid bus bars have a slot while the ring terminals on the flexible wire are circular. The slotted solid bars don't make as full of a contact as the round terminals which may cause increased resistance at the point of contact thereby becoming hotter. Another consideration is the amount of handling on the solid bus bars long before this test was done, any accumulation of oils from the fingers might also have an impact on the resistance. A third consideration is when stringing together the solid bars for the test is that they make a full (better) connection with each other than they make when attached to the posts and therefore don't reveal the weaker connection. I suspect that if one was making a static installation without much flexing, it would be better to have circular holes in the bus bars rather than the slotted holes with the circular holes being a closer fit to the posts thereby making a fuller (better) contact.