Belleville washers for keeping busbars on cells terminals?

noenegdod

Solar Addict
The working rating of the springs I used is 218lb (which is at 60% compressed). I am using a stack in each corner and compressing them with the cells at 100% SOC to the max pressure I want to see which works out to just under 90 kg. Over 3 mm of travel I see the pressure vary from 14 PSI to 9 PSI. I tested my setup with a load cell.


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Thank you for getting involved again! I saw this in another thread about cell compression and at the start of this thread. The testing you are doing is very interesting and helpful for all of us.

I think most of what you have been working on has been working on has been cell compression using belleville washers but what I am wondering about is belleville washers maintaining pressure on the terminals.

Was it you that said the 35inlbs worked out to around 700 lbs of weight pushing the busbar against the terminal? Thank you for that if it was. That is what I am trying to get sorted out. If we are looking for 700 lbs at each terminal the washers used for cell compression are too light for that and need a single washer capable of 700 which it looks like Bob B has got pretty close enough to.

Do you have any recommendations as far as how to apply the washer to the terminals. Im concerned about the washer digging into the softer bus bar material and being prevented from predictably flattening out. This is why I thought the fender washer first would be a good idea.

Thanks again!
 
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HaldorEE

Photon Sorcerer
Thank you for getting involved again! I saw this in another thread about cell compression and at the start of this thread. The testing you are doing is very interesting and helpful for all of us.

I think most of what you have been working on has been working on has been cell compression using belleville washers but what I am wondering about is belleville washers maintaining pressure on the terminals.

Was it you that said the 35inlbs worked out to around 700 lbs of weight pushing the busbar against the terminal? Thank you for that if it was. That is what I am trying to get sorted out. If we are looking for 700 lbs at each terminal the washers used for cell compression are too light for that and need a single washer capable of 700 which it looks like Bob B has got pretty close enough to.

Do you have any recommendations as far as how to apply the washer to the terminals. Im concerned about the washer digging into the softer bus bar material and being prevented from predictably flattening out. This is why I thought the fender washer first would be a good idea.

Thanks again!
I wouldn't do it.

I am using SS 6mm x 20mm set screws (grub hubs). I secured this in the threaded holes of my cells with red locktight. I then use nylock nuts to secure the bus bars. I use an allen wrench to make sure the set screws don't turn any deeper into the cells while I tighten the nuts with a small wrench. From what I have read, a 6mm bolt should not be torqued beyond 5 N. I just take them snug and then give the slight bit more to tighten them up. I am depending on the red locktite to keep the set screws fixed and the nylock portion of each nut to keep them from loosening.

I have seen repeated reports of people stripping out the 6mm threads. 6mm is not a very big fastener and soft aluminum has very low thread holding ability.
 

zzyzx

Apprentice Neanderthal
I am using SS 6mm x 20mm set screws (grub hubs). I secured this in the threaded holes of my cells with red locktight. I then use nylock nuts to secure the bus bars. I use an allen wrench to make sure the set screws don't turn any deeper into the cells while I tighten the nuts with a small wrench. From what I have read, a 6mm bolt should not be torqued beyond 5 N. I just take them snug and then give the slight bit more to tighten them up. I am depending on the red locktite to keep the set screws fixed and the nylock portion of each nut to keep them from loosening.

I have seen repeated reports of people stripping out the 6mm threads. 6mm is not a very big fastener and soft aluminum has very low thread holding ability.
So, my current thinking based on what you (and others) have said is to use Loctite 263 (includes primer) to secure the SS grub screw to the aluminum threads. Seems simple.

Now, I'm wondering if it is possible to measure the amount of torque (using your load cell) that finger-tightening can produce, using a cell terminal, grub screw, busbar, and flange nut (which I am planning to use)? I'm curious if maximum finger-tightening (thumb & index finger) can reach 5nm without the use of a wrench?

The reason I ask is that you may be somewhere, with a battery that needs tightening and the only tools available are the ones that are always with you . . . your fingers! If possible, I would measure both left & right hands, with and without gloves. I would do the same for wives, as they seem to always be near! 😂
 
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