Copper Strapping as BusBars?

[Xhumeka]

I have four 25Ah LiFePo4 cells that I want to use temporarily as a small 12v trolling motor battery. I expect no more than 30 amp draw max, mostly 20 amp continuous.

I'm in a remote area and don't have proper busbar material on hand (or handy), so I was thinking of connecting the cells using 8 gauge solid copper wire, but while rummaging through my shed I found this:

I searched these forums and found only a couple random posts referring to these ( such as this post ) so I thought I would make a separate thread to discuss.

The copper strapping I have is pure copper, 22 gauge. I believe this is approximately 1/32" thick, so if I were to use 4 per connection, that would be 1/8" thick in total. The nice thing about the strapping is that I could use the existing holes for the posts.

Stick with the 8 gauge wire, or use the strapping? Thoughts?

 

[John Frum]

I have four 25Ah LiFePo4 cells that I want to use temporarily as a small 12v trolling motor battery. I expect no more than 30 amp draw max, mostly 20 amp continuous.

I'm in a remote area and don't have proper busbar material on hand (or handy), so I was thinking of connecting the cells using 8 gauge solid copper wire, but while rummaging through my shed I found this:

I searched these forums and found only a couple random posts referring to these ( such as this post ) so I thought I would make a separate thread to discuss.

The copper strapping I have is pure copper, 22 gauge. I believe this is approximately 1/32" thick, so if I were to use 4 per connection, that would be 1/8" thick in total. The nice thing about the strapping is that I could use the existing holes for the posts.

Stick with the 8 gauge wire, or use the strapping? Thoughts?

How wide is it?

 

[Xhumeka]

How wide is it?

Thanks, I should have mentioned that - it's 1/2"

 

[MisterSandals]

It does not matter what the copper is called, it all depends on the cross section of the material. I think your measurements (guesses?) should be made at the thinnest spot, where the holes are.

However, if you doubled it up so solid areas overlapped the holes, it would be more consistent.

Give it a go and keep an eye (finger?) on it to watch for temp increases. If it gets warm, it’s too small and will (aside from being a fire hazard if hot), introduce voltage drop and energy loss in the form of heat.

30A is about 360W so it would not take a lot to handle this.

 

[John Frum]

Thanks, I should have mentioned that - it's 1/2"

1/2" x 1/32" ~= 0.015625 "
0.015625" ~= 10.080625mm2
10.080625 mm2 ~= 8 awg

But... your busbar is full of holes which will make it less conductive.
But... it has no insulation so it can dissipate heat better.
But.. you need less joinery to do this solution.
Oh and you can double it or triple it, but there will be resistance between the layers.
Answer is blowing in the wind.

 

[Xhumeka]

Happy to report the copper strapping did the trick nicely! I was expecting the need to double-up, but I started off with just a single strap and was happy with the results. I ran the 30lb trolling motor at max speed non-stop for about 45 mins and the strapping stayed ice cool the whole time.

 

[Xhumeka]

I'm about to run a test on a pair of Daly Parallel BMS modules, and I want to test them using battery banks of different capacities. I decided to use some of these 25 Ah cells for one of the banks, and since I want to mis-match voltages and SoC (to test the parallel unit) between banks I needed to discharge an 8s25Ah battery pack.

Since I noticed no noticeable heat from this copper strapping at 25 Amps, I was curious to see how the strapping would fair near the cell's limits (3C/75 Amps).

After 15 minutes of a solid ~73 Amp draw the copper strapping temp only increased to 86.2 degrees!! (70 degree room temperature to start with). I was pretty impressed! I left a "standard" busbar that comes shipped with the cells in the middle of the pack to use as a reference, and it remained basically the same temp as the strapping during the whole test.

Definitely the cheapest busbars I've found for these cells

 

[Bud Martin]

Are they pure copper or copper plated steel?
When you cut it does the side view show copper?
I look up this DAHL brand, the price of this 'Copper' is about the same as 'Steel Copper plated' one.

 

[Xhumeka]

This Dahl brand is pure copper - after cutting I can see it's copper all the way through.