replacement cell taller than the others

[scott harris]

I have a 8s battery built with 280AH prismatic cells. I have decided to replace a poor performing cell but the replacement is about 2 mm taller than the others. Can I place a washer between the busbar and the terminal of the two neighboring cells to make up the difference? The washers are common washers made of steel i would guess. I am afraid that the conduction of steel, being lower than the terminal or the busbar may cause a problem.

Thanks,

 

[42OhmsPA]

No.
You could shim the older 7 up from the bottom with flexible cutting board or use flexible busbars for that small of a difference.

 

[DIYrich]

Flexible busbar.

 

[Supervstech]

Post pictures of what you have.

 

[Lt.Dan]

I don't recommend it, but I have bent the bus bar slightly to accommodate for different height in cells, just make sure it sits PERFECTLY on the terminal

 

[robbob2112]

Stainless steel between the aluminum battery tops and the bus bars?

Short answer is no, never place a washer between..particularly a poor conducting metal like SS that will heat with current. Fire waiting to happen.

In a pinch I've used pure copper washers between lugs and MRBF fuses where the surface area isn't great.

Between different metals you risk galvanic corrosion, but you probable already have that unless your busbars are aluminum. If your busbars are copper you could probably get away with pure copper washers as shims.

In any case no-ox-id special on all contact surfaces- thin coating

And if you went this route I would monitor and test at max amps for a while to make sure they were no hotter than any other cells.

Make sure you have an appropriate type size fuse protecting the string and a extinguishing agent handy

 

[Supervstech]

I have 8 280Ah cells of varying heights... i built layers of thin cutting board sheets from the dollar store and made all heights equal.

 

[scott harris]

lots of good answers. thanks for the help. In the end i went with flexible bus base between cell 4 and its neighbor because i had the necessary stuff to make them.