Weird bus bar idea

Leon

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Dec 15, 2019
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Made a bit of progress today. These bus bars are made for both halves of the battery, just in place for a test fit now - terminals are not cleaned properly yet. I still have to make the fancy ones for the ends of the pack. It was a bit disconcerting when I realised these plates are the right size to simultaneously short out three cells at once. The lumps of foam prevent that for now, I'll probably devise something more permanent.

I want to put something between the edges of the plates and the plywood panels, the air gap is pretty small and I don't think the wood would be a perfect insulator. Maybe some tape on the edges of the plates will do.

I'm also considering whether to put in some small nuts and bolts to attach the balance leads to the centre of each plate, rather than using the cell terminal posts for this.

You can see the corner of my new 3500W inverter in this photo. Delivered to my house in NSW from Shenzen in under 7 days. It takes longer than that to get things from Brisbane or Melbourne.

DSC_0910.JPG
 

toms

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Jul 24, 2020
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Yep, if you short that out you’ll spread molten aluminium all over the area!
 

stienman

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Jan 6, 2021
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Why don’t you use infinite parallel pack as I do. I can add any number of new 16s packs I want at any time without any stop of the working system. What do you think?

View attachment 55264

Interesting, but I'd rather have at least two battery packs, so I don't have to choose between having power and working on a live system.

I also don't see any clamping, and the use of rigid bus bars means that expansion and contraction - which is normal and expected with each cycle - will ultimately damage the terminals and internal cell connections.

If one battery in the middle decides to balloon, you're likely to experience terminal damage on the surrounding 6 cells.

I'm not even sure how you'd clamp it as a whole with the gaps on the ends. If you add spacers the spacers won't expand and contract like the batteries adjacent, which isn't much better than leaving them open. I suspect a good clamping fixture would be clamping each row, but then you'd need supports in the middle occasionally, which you can't have due to the cell staggering.

Obviously it works for you, and chances are good it'll meet you needs for years, just with a reduced lifetime and overall performance, but I'm not sure the convenience you get from it is worth the problems it causes.
 

Leon

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Dec 15, 2019
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Here's how I'm preparing the cell terminals. Let me know if I'm mucking it up.

As supplied:
DSC_0914.JPG

800 grit paper glued on the end of a dowel:
DSC_0918.JPG

I'm putting a drop of lanolin-based corrosion inhibitor on the abrasive before attacking each terminal. After abrading each, I wipe the tool clean-ish and apply more sheep sweat. This is what the terminal looks like covered in residue:

DSC_0915.JPG

This is the result after the first wipe with a lanolin-coated cloth to remove residue:
DSC_0919.JPG

Bus bars will get the same treatment, made much easier by the absence of a threaded post in the middle. I'll give it all another wipe over before final assembly. I'm using the lanolin because I have it and it is approved for electrical applications. Anything more specialised is a bit harder to get, with the latest virus outbreak.
 

JimStLaurent

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Apr 19, 2021
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Leon, I applause your efforts. The lapping technique you've developed is flattening and polishing the mating surface nicely.
But the oxidized particles you removed should not stay. Clean up the residue and apply the antioxidant with a cloth glued to your tool.
Lighter is better, just need a gas tight seal.
 

Leon

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Dec 15, 2019
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Leon, I applause your efforts. The lapping technique you've developed is flattening and polishing the mating surface nicely.
But the oxidized particles you removed should not stay. Clean up the residue and apply the antioxidant with a cloth glued to your tool.
Lighter is better, just need a gas tight seal.
Thanks Jim, but don't worry, I have done multiple rounds of cleaning and coating to ensure nothing but antioxidant is left behind. Difficulty of cleaning is one of the real downsides of the welded studs. Time will tell if I have been fastidious enough.
 

Leon

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Dec 15, 2019
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Low precision annealing with soap and a gas stove.

DSC_0912.JPG

I've wall-mounted the battery. Since I was originally going to build the battery in a less-skinny configuration, I had not considered this location. it's going to save me lots of space and is slightly closer to my solar panels. I think I'll build a box around the whole setup once the inverter and other gear is installed.
DSC_0913.JPG
 

curiouscarbon

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Jun 29, 2020
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looks friggin awesome! very compact. very sturdy looking constraint.

only critical feedback, are the bolt threads covered on the inside? the blue wrapper has been pierced in one other case seen on the forum. they added a plastic cylinder/tube thingy on the outside of the threads to mitigate the hazard (not saying there's a hazard in your case, but just mentioning because it popped out to me).

great work.
 

Leon

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Dec 15, 2019
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looks friggin awesome! very compact. very sturdy looking constraint.

only critical feedback, are the bolt threads covered on the inside? the blue wrapper has been pierced in one other case seen on the forum. they added a plastic cylinder/tube thingy on the outside of the threads to mitigate the hazard (not saying there's a hazard in your case, but just mentioning because it popped out to me).

great work.
They are covered. I used some clear PVC tubing that fits perfectly over the rods. It's hard to see in the photos.

Thanks for the scrutiny, it helps me to worry less knowing there are more eyes than just mine on this project.
 

curiouscarbon

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Nice.

Also, very big commendation on your terminal preparation. Thank you for posting the picture of the dowel tool you made. The terminals look great.
 

Leon

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Dec 15, 2019
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Actually now that I think about it, the only cells I have side-by-side are connected in parallel blocks, so the cases should be at the same potential anyway, right?
 

curiouscarbon

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If you have PVC covering the inner threads and a supplementary plastic sheet between the cells in addition to the blue wrap, I would reckon shorting from the sides has been mitigated.

Correct as far as I know, the aluminum case is Vbat+ positive on most cells like that, and you’re already connecting the proper positive terminals with busbar, so adjacent paralleled cells touching each other should not pose that big of an issue.

I’m learning too 🙂
 

Aabshir

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Mar 17, 2021
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17
Why don’t you use infinite parallel pack as I do. I can add any number of new 16s packs I want at any time without any stop of the working system. What do you think?

View attachment 55264
That is very unique way of doing things. although its almost impossible to understand how the 16s is connected
 
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elvis_asaftei

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Jul 5, 2021
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That is very unique way of doing things. although its almost impossible to understand how the 16s is connected
cells are aligned in S on 2 rows in series and also each cell is linked in parallel with the other 3 in parallel . so it is a 4P than 16S and on 2 rows in S for easier connection and also each 2 rows you can see the parallel mount ... put on a paper the connections ... like that you can add an infinite number of new rows at runtime without disconnecting anything ... got it ?
 

kromc5

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Jul 2, 2020
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I was on the the laptop and could not see it was on page 3, I do like the clamping system.
 
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