Lifepo4 terminal bars

[Rider]

Anyone see a down side to using awg 8 bare copper between cells in this setup?

In order to use bare copper, you'd have to terminate it with lugs. The length of the wire with lugs is far longer than the distance between cells. While it would work, it would be cumbersome to install and look a bit messy. Buss bars are short and clean.

 

[Rider]

If you had access to a kiln or something else hot, like 2000*F, you could melt copper and pour your own custom bus bars.

 

[Newenough]

Aluminum is much more conductive than steel (by a lot) but it has one big downside, which is oxidation when conducting electricity. As a bus bar I use stainless hardware for my post and have each coated in Dupli-coat (one red, one black) to protect from oxegen, but the terminals on the batteries are steel (so different metals already) and coating all those little bars from oxygen exposure may be a little tougher, but it is worth putting some thought into for sure. Aluminum flat bar is pretty cheap too.

I have been looking everywhere for a supplier of busbars for my banks and I cannot find one. I love the bus bars that come with the raw cell kits but I can never seem to source them. :/

I thought for sure a quick Google or Amazon search would get me multiple sources easy. Boy was I surprised...

Think it could be that cells are not standard enough in size and just very to much by maufacturer? A millimeter or two is a huge difference when assembling these packs. Which would also explain why these oem's only sell them with the batteries or on their site to go with them?

 

[robaroni]

As most are aware aluminum is a good conductor (what a lot of wire uses these days) and it's very easy to work with. Why not buy some 1/4"×1" bar stock at ace or home depot and use it for the battery interconnect buss bar? I'd slot the holes a little for thermal expansion. My guess is that the terminals on these aluminium cased prismatic cells (pictured above) are aluminium?

Aluminium: Inherently good for bus bars - Schneider Electric Blog

Are aluminium bus bars really as conductive and rugged as copper? How do aluminium busbars handle heat? Inherent advantages of aluminium for bus bars?

blog.se.com

I think it's a good idea, you might get better prices on eBay or Speedy Metals.com. Expansion is greater but I've seen industrial applications using aluminum flat stock, just allow for the expansion. Also use some Noalox around the connections like electricians do in house wiring. What you have to watch is dissimilar metals where there's a possible voltage differential as the current rises.

 

[Craig]

As most are aware aluminum is a good conductor (what a lot of wire uses these days) and it's very easy to work with. Why not buy some 1/4"×1" bar stock at ace or home depot and use it for the battery interconnect buss bar? I'd slot the holes a little for thermal expansion. My guess is that the terminals on these aluminium cased prismatic cells (pictured above) are aluminium?

Aluminium: Inherently good for bus bars - Schneider Electric Blog

Are aluminium bus bars really as conductive and rugged as copper? How do aluminium busbars handle heat? Inherent advantages of aluminium for bus bars?

blog.se.com

That's exactly what I do never had a problem plus you can make it anyway you wish.

 

[jbeletti]

Here's a source of various thickness, length etc. of copper bar stock. Check out the tin flashed product. Tinning will help guard against corrosion.

1/4" x 1" Copper Full Round Edge 110-H02 Tinned Full Round Edge | Online Metals

Order 0.25" x 1" Copper Full Round Edge 110-H02 Tinned Full Round Edge stock today on our website. Buy online with fast shipping direct to your door.

www.onlinemetals.com

 

[K W]

I like these braided straps: http://store.evtv.me/proddetail.php?prod=braided60mmkit A bit pricy, but they don't transmit mechanical stresses between cells via their terminals. I have also made my own by purchasing the tined braid and smashing Cu water pipe over the ends, then soldering and drilling. Use a good heatsink to keep the solder from flowing into the braid.

 

[robaroni]

I like these braided straps: http://store.evtv.me/proddetail.php?prod=braided60mmkit A bit pricy, but they don't transmit mechanical stresses between cells via their terminals. I have also made my own by purchasing the tined braid and smashing Cu water pipe over the ends, then soldering and drilling. Use a good heatsink to keep the solder from flowing into the braid.

It seems to me if I were making a mobile installation I'd use something like these but it might be overkill in a stationary system, although if you have the bucks why not?
If you're worried about stresses just leave a small gap between batteries for expansion.

 

[Johan]

I like these braided straps: http://store.evtv.me/proddetail.php?prod=braided60mmkit A bit pricy, but they don't transmit mechanical stresses between cells via their terminals. I have also made my own by purchasing the tined braid and smashing Cu water pipe over the ends, then soldering and drilling. Use a good heatsink to keep the solder from flowing into the braid.

Braided straps seemed to be a good idea to me too, but experienced people [1,2] may make the case that the cells should be tightly compressed to each other [2], eliminating a most of the relative movement between cells and thus the need for such straps. Or not?

Note (bolding is mine):
From [1]: "Use solid copper links in marine installations. Braided straps, such as earthing straps, even tinned, are not a good idea. They have a lesser cross-section than a solid conductor and will not age as well in the marine environment. They are bound to corrode and heat up severely one day."

Maybe heat-shrinking (with glue) these straps prevents/delays this type of degradation somewhat?

Switching to exaggerated theoretical mode (I can't help it):
Note the non-zero (~30°) "braid angle" (in the extreme case: compare to a wire-wound resistor having a near-90° "winding angle"): The effective cross-section perpendicular to the main current flow may be (cos(30°) = ~87%) of the "apparent" strap cross-section while the actual strands are (1/cos(30°) = ~15%) longer than the length of the strap. Both effects could increase the resistance (1/87% x 1.15% = factor 1.33) compared to using the "apparent" dimensions (L x W x T) of the strap. Not to mention the added effect of undulation due to the interlacement.

Anyways so what are the dimensions, materials and current rating of that braided strap?

[1] http://nordkyndesign.com/assembling-a-lithium-iron-phosphate-marine-house-bank/
[2] https://marinehowto.com/lifepo4-batteries-on-boats/