8 cells, running 24V system with inverter, but 200A would be really really pushing it.
In an RV/offroad truck, btw.
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Improving Contact Area on Welded Stud Pads
- Thread starter Horsefly
- Start date
In an RV/offroad truck, btw.
curiouscarbon
Science Penguin
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Hi!
Im amateur trying for long operational lifetime LiFePO4 DIY ESS. so i could be very misinform!
Increase in ability to repeatedly connect and disconnect the terminals vs tapped aluminum, that feels like a real gain to me.
however, the reduction in surface area going to the pedestal does make me less inspired.
one person did some practical tests, and posted temperatures. if i find it, will link.
anyways, 0.3C continuous discharge seems like it might be what i try to target, based on reading about the purported self heating of these type of cell.
temperature of cell material drives calendar aging strongly, so contact resistance is extra undesirable imo.
may i ask, is it only the surface area holding you back?
went forward with 12 of these large format cells with stainless steel studs, and in person, the connection surface area look so puny and i would not want to run >100A through it without rigorously checking each connection's temperature
increased torque tolerated by stainless steel stud kinda offsets the surface area, but i dislike needing to try on sustained super tight connector, although of course will use nylon lock fastener even though they throw torque observation off a bit. me want larger surface area And strong connector!
have consider the mg-847?
847 - Carbon Conductive Assembly Paste
Resistivity of 23 Ω.cm Improves electrical connections between irregular, pitted or corroded surfaces Ensures electrical contact between loose or vibrating parts Prevents arching, pitting, hotspots and welds Inhibits corrosion Fills gaps Can be used on vertical surfaces Silicone-free
www.mgchemicals.com
to quote their material
https://www.mgchemicals.com/downloads/tds/tds-847.pdf datasheet
i dont actually see it say that there is no h2o in it. dunno!
interesting, thank you for sharing. i have not worked with carbon fiber around graphite or aluminum. the mg-847 paste seems to clearly claim that it improves the conductivity and long term stability of connections, i wonder how the chemistry works with the grease in the mix. i have no long term testing data from using that carbon assembly paste, and plan on using it on upcoming build of 300Ah style cells with stainless steel threaded terminals to promote long term happy conduction time. as well, using crimped lugs for flexible connection of like two or three 6awg fine strand tinned copper silicone jacket conductors eg very flexible.
anyways i heard many of these class cells heat up a lot past 0.3C current with order of 10-30W internal heating and more as approaching 1C, which drives aging, so i will probably shoot for continuous 0.3C or ~100A or ~320 Watt per cell. so 1,280 W for 4 cell pack which is pretty low compared to what many people here do?
annnnyyways rambled enough, maybe i should stop typing and start building!
Hi!
Im amateur trying for long operational lifetime LiFePO4 DIY ESS. so i could be very misinform!
Increase in ability to repeatedly connect and disconnect the terminals vs tapped aluminum, that feels like a real gain to me.
however, the reduction in surface area going to the pedestal does make me less inspired.
one person did some practical tests, and posted temperatures. if i find it, will link.
anyways, 0.3C continuous discharge seems like it might be what i try to target, based on reading about the purported self heating of these type of cell.
temperature of cell material drives calendar aging strongly, so contact resistance is extra undesirable imo.
may i ask, is it only the surface area holding you back?
went forward with 12 of these large format cells with stainless steel studs, and in person, the connection surface area look so puny and i would not want to run >100A through it without rigorously checking each connection's temperature
increased torque tolerated by stainless steel stud kinda offsets the surface area, but i dislike needing to try on sustained super tight connector, although of course will use nylon lock fastener even though they throw torque observation off a bit. me want larger surface area And strong connector!
have consider the mg-847?
water is not included in it as far as i'm aware847 - Carbon Conductive Assembly Paste
Resistivity of 23 Ω.cm Improves electrical connections between irregular, pitted or corroded surfaces Ensures electrical contact between loose or vibrating parts Prevents arching, pitting, hotspots and welds Inhibits corrosion Fills gaps Can be used on vertical surfaces Silicone-free
View attachment 78161
to quote their material
https://www.mgchemicals.com/downloads/tds/tds-847.pdf datasheet
i dont actually see it say that there is no h2o in it. dunno!
interesting, thank you for sharing. i have not worked with carbon fiber around graphite or aluminum. the mg-847 paste seems to clearly claim that it improves the conductivity and long term stability of connections, i wonder how the chemistry works with the grease in the mix. i have no long term testing data from using that carbon assembly paste, and plan on using it on upcoming build of 300Ah style cells with stainless steel threaded terminals to promote long term happy conduction time. as well, using crimped lugs for flexible connection of like two or three 6awg fine strand tinned copper silicone jacket conductors eg very flexible.
anyways i heard many of these class cells heat up a lot past 0.3C current with order of 10-30W internal heating and more as approaching 1C, which drives aging, so i will probably shoot for continuous 0.3C or ~100A or ~320 Watt per cell. so 1,280 W for 4 cell pack which is pretty low compared to what many people here do?
annnnyyways rambled enough, maybe i should stop typing and start building!
This is a great video on corrosion.
Keep in mind my comment about bank heated 24/7 and the lack of moisture there would be.
He's discussing 2 dissimilar metals/materials. Aluminum terminal + copper lug/bar + carbon paste (+ whatever else is in the paste one is using) on the terminals would be a min of 3 dissimilar metals/materials.
At 11:00 he makes one of the best comments about encapsulating or sealing (paste) connections. I've opened 5-10 year old connecions and seen it fail time after time.
curiouscarbon
Science Penguin
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- Messages
- 3,022
thank you, will check out this video, cheers
I hope you don't mind asking this question here.
Is the welding of the studs or the drilling/cutting of the threads done by the manufacturer of the cells?
Or is it done by the suppliers that are selling these batteries to us?
I have ordered 16 EVE 280Ah cells and they asked me after i confirmed the order which kind of welding i would prefer.
Choice was between "stud" and "screw hole".
They said they could no longer provide "threaded holes" since " .... EVE factory has stopped producing the old LF280ah for several months, so there is no threaded hole 280ah on the market now."
Is that really true?
To me it seemed that the manufacturer would sell the batteries with no preparation at all and leave that to the customer!
Can anyone share more facts about this?
Thank you very much...
Joerg
Is the welding of the studs or the drilling/cutting of the threads done by the manufacturer of the cells?
Or is it done by the suppliers that are selling these batteries to us?
I have ordered 16 EVE 280Ah cells and they asked me after i confirmed the order which kind of welding i would prefer.
Choice was between "stud" and "screw hole".
They said they could no longer provide "threaded holes" since " .... EVE factory has stopped producing the old LF280ah for several months, so there is no threaded hole 280ah on the market now."
Is that really true?
To me it seemed that the manufacturer would sell the batteries with no preparation at all and leave that to the customer!
Can anyone share more facts about this?
Thank you very much...
Joerg
Horsefly
Solar Wizard
I'm pretty sure either the welded studs or the threaded holes are done by the sellers, not the manufacturers.
For last set of Eve 280Ah cells that I bought from Amy Wan @ Luyuan, I asked about switching from the welded studs to the threaded holes (my first batch had studs), and she said that Eve had started telling sellers that they did not recommend the threaded holes due to the risk of damage to the cell and the low strength of the threaded holes.
I think the majority of the cells from the manufacturer go to car manufacturers or other large ESS systems where the buyer has their own equipment to weld to the flat terminals of the cells.
Thank you for this information.
I also guessed that the manufacturers will leave all "customization" of the terminals to the customer.
I think the merchant where i ordered the batteries just don't want to do the drilling/tapping anymore.
It is a lot faster with the laser welding machine.
So in my case i will cancel the order if they are not willing to sell batteries with threaded holes.
I could even drill and tap myself if they think it is too costly.
Funny though, most of their latest offerings show terminals with threaded holes...
I also guessed that the manufacturers will leave all "customization" of the terminals to the customer.
I think the merchant where i ordered the batteries just don't want to do the drilling/tapping anymore.
It is a lot faster with the laser welding machine.
So in my case i will cancel the order if they are not willing to sell batteries with threaded holes.
I could even drill and tap myself if they think it is too costly.
Funny though, most of their latest offerings show terminals with threaded holes...
Well, I got thru 7 pages of this thread...are the washers the best solution? And if so do you still have any of these?
I got the 230A Eve cells with the welded sockets and grub screws. I had concerns about the small mounting area but no one mentioned anything about it.
I wouldn't mind disassembling and reassembling with the washers, and apply some oxguard on the terminals. And I have copper ring terminals on my cables. I could re-make them with tinned terminals, but gee, what a hassle.
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Horsefly
Solar Wizard
You can buy 1/4" aluminum washers that fit right on the M6 stud and extend the existing 11mm pad by quite a bit. This is what I settled on, although I can't remember (and can't find an email about) where I got them. At the time Dan wanted almost $1 per washer for the ones he had, which was just too much.
Horsefly
Solar Wizard
I found where I got them: Bolt Depot. https://www.boltdepot.com/Product-Details.aspx?product=27373
$2.90 + shipping for 25 washers. I paid $2.52 last time. Got 50, and about half the $10 total was for shipping.
stienman
Mostly Harmless
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- Jan 6, 2021
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Nope, just my opinion. Others are still pursuing crush washers, but no one's posting data that proves any of the hypothesis posted here - including me.
My point is that if you're running your battery packs at under 50A (so a 0.2C load for 271AH batteries) then the existing stud is sufficient.
If you're running the batteries at over 0.2C the correct solution is more battery packs - not a better connection to your current batteries.
Yes, it would be nice if the studs provided a better contact, and yes, adding crush washers does make up for that shortfall, but I just don't see the point.
However I'm setting up my batteries with aluminum bus bars and in a month or so when I have time I'll do a load test and do a thermal image of the battery pack and bus bars to confirm I don't have any hot spots.
jsmetalcraft
New Member
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A tight 6mm fit. Not used or ordered, just what I found searching around.
www.mcmaster.com
McMaster-Carr
McMaster-Carr is the complete source for your plant with over 595,000 products. 98% of products ordered ship from stock and deliver same or next day.
Comforting...
I've done this at 72-75A continuous, testing out performance, looking for hot spots with an infrared thermometer gun. The battery runs cool, the ring terminal on the 4awg wire after the fuse to the inverter got to 80* from 67 +/- starting/ambient, and the housing on the inverter was 102. THAT is where the heat is! LOL
I'm not too worried. Probably more concern for the copper terminals on the aluminum post contacts for plus and minus over the long haul. My house has aluminum wiring so I'm familiar with using ox-gard or similar with connections in j-boxes. I probably even have some on hand, but didn't think to use it on the battery build.
I too considered replacing the thin tin-coated copper bus bars that come with the cells from Docan. I kind of wanted to drill and tap bars for the balance leads, but that didn't make sense with those bus bars. I'm torn whether to do anything more with what I have.
triplethreat
Solar Enthusiast
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- Oct 12, 2021
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I just ordered a package of these.....thank you for posting them. And yes....a "tight" 6mm but that is what small rat tail files are used for. I had just started to order some on Amazon, but they looked pretty rough and likely some sanding/honing would have been required, not to mention that they were 1/4" and the inside diameter was .265. These will fit like socks on a rooster.A tight 6mm fit. Not used or ordered, just what I found searching around.
McMaster-Carr
McMaster-Carr is the complete source for your plant with over 595,000 products. 98% of products ordered ship from stock and deliver same or next day.
Wanna sell half of 'em? LOL
I sure don't need 50 of them.
Horsefly
Solar Wizard
Really? These have an I.D. that is 0.03" smaller than a 1/4" washer. I think this is getting a bit silly.
You are right that these will have to be filed out in order to fit on the 6mm studs. But if I assume they are exactly 6mm, my math tells me that you might gain about 9% in surface area overlap with the 11mm pad, over the 1/4" washers (0.265" I.D.). I really don't think it is worth it, especially since you're going to lose more than that in the surface overlap with your bus bars.
Seriously, I think we are making this harder than it needs to be.
Oh, and roosters don't need socks either.
I'm thinking aluminum bus bars might be a better option. Anyone want to recommend a width and thickness? I can just make them out of standard flat-bar.
I can drill and tap them for the balance wire terminals then, so they're not on the cell posts.
I can drill and tap them for the balance wire terminals then, so they're not on the cell posts.
triplethreat
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I'd be happy to, I don't need 50 of them either.
triplethreat
Solar Enthusiast
- Joined
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Wow....You've got less than zero sense of humor........socks on a rooster! Part of the issue is that I'm not using the buss bar that came with the battery purchase, I'm using copper crimp lugs and 2/0 cable. And the existing buss bars have a lot of slop in the hole also. So I guess maybe my idea....or actually someone else's idea really isn't that bad. You may now return to your grouchy self.
And on the subject of the washers, they should be about .002 smaller inside diameter than the 6mm post and I'm doing a compression jig with 1/8" silicon pads in between the cells for no movement between terminals.
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