I just destroyed $500 worth of batteries by doing nothing.

Barbar0ssa

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Now I need to re-think bus bars. The previous ones won't fit the heavily-bloated cells. Maybe I should make some out of copper pipe?
 

Bleedingblue

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Now I need to re-think bus bars. The previous ones won't fit the heavily-bloated cells. Maybe I should make some out of copper pipe?


I bought copper bar stock. .125 x .75. Think it will handle 300 amps since it is 1 mil thicker than the busbars that come with the cells.

To me beating a copper pipe flat still won't be perfectly flat because of the imperfections. Only the high spots will be making contact.
 

DerpsyDoodler

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I bought copper bar stock. .125 x .75. Think it will handle 300 amps since it is 1 mil thicker than the busbars that come with the cells.

To me beating a copper pipe flat still won't be perfectly flat because of the imperfections. Only the high spots will be making contact.
or use a press. copper is soft metal. It will become as flat as the surface you press it against.
 

shadowsteve

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I bought copper bar stock. .125 x .75. Think it will handle 300 amps since it is 1 mil thicker than the busbars that come with the cells.

To me beating a copper pipe flat still won't be perfectly flat because of the imperfections. Only the high spots will be making contact.
215A according to this chart that I use

 

shadowsteve

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Now I need to re-think bus bars. The previous ones won't fit the heavily-bloated cells. Maybe I should make some out of copper pipe?

I annealed some 1/2" hard copper water pipe and flattened it out. It flattens better annealed than not. It measured out to about 36sq mm which is between 2AWG (33.6) and 1AWG (42.2) wire. Three layers would be about 4/0 AWG
 

Barbar0ssa

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I just did some measuring and my original bus bars are only 16mm. They will be limited to about 70a. I think pipe is probably the way to go as even 1/2" pope is several steps higher rating than what I had.
 

Steve_S

Offgrid Cabineer, N.E. Ontario, Canada
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I just did some measuring and my original bus bars are only 16mm. They will be limited to about 70a. I think pipe is probably the way to go as even 1/2" pope is several steps higher rating than what I had.
The two most common sized busbars supplied with these cells are 15mm Wide x 2mm Thick or 20mm W x 2mm Thick.
I've used 0.125"x-.750" 110 copper bar stuck to make busbars. I have gone up to 0.250 thickness and that was of NO BENEFIT !
But then again, I have multiple packs in the battery bank, so they divide/split load & charge quite nicely.

MANY Online Metal Dealers carry 110 Pure Copper and often available even with Tinning or Nickle plated.
COPPER C110 FLAT BAR ASTM-B187 0.125" x 0.750" costs me $4.10 per foot @ todays price.

Lessons Learned: I'll put it this way, you could NOT pay me to put a crushed copper pipe on my cells. BODGES like that are for "special folk".
 

Just John

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I agree with pretty much all of that .... but would add that one of the things that causes the cells to be damaged during top balance is loss of patience .... so lets crank up the voltage on the power supply a little to speed things up.

The other thing is .... hey, I'm not getting anywhere near as much current as I should be .... so, lets crank up the voltage a little to get more current.

I was having problems with getting the current I should be from my power supply .... replacing the crappy alligator clips pretty much doubled my current.
This, 100%.

Bad cables and connections inspire people to do stupid things.
 

A.Justice

Swears he didn't start that fire.
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.... one of the things that causes the cells to be damaged during top balance is loss of patience .... so lets crank up the voltage on the power supply a little to speed things up....
I am definitely an inpatient person, but it kills me to see people cranking up the voltage, when, most of us spent hundreds, if not thousands of dollars on cells. I bought a second bench power supply, so I could charge at 2x the speed. It's a very small cost considering what I spent on the system.

If you want faster balancing, just get another charger, you can always sell it on here or eBay later.
 

featherlite

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Jul 10, 2020
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I was concerned about expansion, so I made these for my 2P4S bank. Might work for you.
I really like your bus bars!

Could you please provide a bit more explanation about:

(i) how you sandwiched the braided cable between what appears to be aluminum flat stock (I am wondering if you squeezed the sandwich using a conventional bench vise or used a press and die),

(iii) what is the material of the cables (stainless?)

(ii) how the BMS studs are affixed to the bus bars by what appears to be bolts or screws with the heads under the bus bar (I am wondering about clearance between the bottom of the bus bar and the cell )?

Thank you!
 

Just John

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I really like your bus bars!

Could you please provide a bit more explanation about:

(i) how you sandwiched the braided cable between what appears to be aluminum flat stock (I am wondering if you squeezed the sandwich using a conventional bench vise or used a press and die),

(iii) what is the material of the cables (stainless?)

(ii) how the BMS studs are affixed to the bus bars by what appears to be bolts or screws with the heads under the bus bar (I am wondering about clearance between the bottom of the bus bar and the cell )?

Thank you!

I would assume plated copper.

 

Barbar0ssa

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I didn't compress them at all. I loosely paralleled them and charged them for days up to 3.6v at 10amps. I left them until there was 1/2 amp current. I can't believe they went back to the normal dimensions!
 

100 Proof

"Please Lord, don't let me do something stupid."
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Feb 14, 2021
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I really like your bus bars!

Could you please provide a bit more explanation about:

(i) how you sandwiched the braided cable between what appears to be aluminum flat stock (I am wondering if you squeezed the sandwich using a conventional bench vise or used a press and die),

(iii) what is the material of the cables (stainless?)

(ii) how the BMS studs are affixed to the bus bars by what appears to be bolts or screws with the heads under the bus bar (I am wondering about clearance between the bottom of the bus bar and the cell )?

Thank you!
They are made of tin plated flat braided copper that I bought off of ebay at the following link -> https://www.ebay.com/itm/293492808117

They are sandwiched inside of 1" copper pipe segments that I fully annealed with a propane torch, cleaned in my brass tumbler, then tin plated on my bench top.

The pipe segments were then compressed onto the braid on a 12 ton press. That press did NOT have enough pressure to make a cold weld over 1-in^2 as discussed in upnorthandpersonal's directions, so I made a spacer out of a stainless windshield wiper stiffener to concentrate the pressure to attain a cold weld near the edges (the compressed lines in the photo). CAUTION- I learned if you compress right at the edge, you will cut the copper braid, so bring it back just a bit.

I cleaned the battery terminals with my own version of Filter Guy's Binford 4800, coated with No-Ox-Id, and torqued the stud nuts to 75 in-lbs.

As I did not want anything except the battery terminals stacked together, I drilled and tapped for #6 screws at the inside edge of each busbar for the BMS sense wires. Each of the #6 screws was installed from the bottom with a nut on top to secure it, then the sense lead terminal, then another nut. The busbars are wide enough that there is plenty of clearance to the cell.

Frankly, these busbars are probably overkill, but I'm happy with how they turned out and I do not worry about the cell expansion at all. I do not get any consequential heating of the terminals with a constant 150A load on the battery.
 
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