Compare Resistance/Throughput?

[HRTKD]

I'm gearing up to make my own bus bars for between the terminals of my cells. I'm currently using the bus bars that came with the cells from Xuba.

How do I determine that my new bus bars are better than the old bus bars? Is it as simple as using my multimeter to measure resistance? I'm not sure if my meter has enough sensitivity. It goes from 600Ω to 60MΩ.

 

[John Frum]

Stress test with planned max current.
Use and ir thermometer to measure temperature.

 

[Steve_S]

XUBA only 2mm thick, so I doubled those up AFTER I deburred the punched holes whhich all had small edges, just enough to be problematic.
I also got 1/4" 3/4" 110 Copper to make my own for other cells. Drilled with a Drill Press and chamfered holes for good clean connections. I went ver board a bit but that's better than under doings it.

 

[HRTKD]

I doubled up the Xuba bus bars also, after verifying the surface was clear of any obstructions. I'm not convinced that the bus bars are perfectly flat. Alternatively, the terminals could also be the culprit for not being a flat surface.

Anyhow, I was hoping for a point-to-point measurement to see if the new bus bars were better or worse than what I started with. I have an IR thermometer. Coming up with enough load to really stress the system could be interesting. I didn't design the system for high C discharge. Instead, it's for long term discharge in the absence of sunlight over a period of days, like a blizzard.

 

[ArthurEld]

I doubled up the Xuba bus bars also, after verifying the surface was clear of any obstructions. I'm not convinced that the bus bars are perfectly flat. Alternatively, the terminals could also be the culprit for not being a flat surface.

Anyhow, I was hoping for a point-to-point measurement to see if the new bus bars were better or worse than what I started with. I have an IR thermometer. Coming up with enough load to really stress the system could be interesting. I didn't design the system for high C discharge. Instead, it's for long term discharge in the absence of sunlight over a period of days, like a blizzard.

I don't expect to use high C rates either. And I am probably going to use .125 X .75 copper bar from Grainger. They're close so I can pick them up.

 

[Steve_S]

IF using 280AH EVE cells and you want to make up your own Busbars or have bar stock cut to size. LIKELY DOES NOT APPLY TO OTHER BRANDS.
IF making a BLOCK PACK the cross over busbar needs to be 4.250" long.
IF just building a Straight S Pack (in series only) the bar legths should be 3.750" long.

I get the 110 Copper pre-cut to size for easy, simplicity & consistency... Uniformity is a good thing in electrical tinkering.

 

[gnubie]

You'd be struggling to get a reliable reading with a typical multimeter, or even a good one really. Pass a few amps across the setup and measure the voltage dropped. If it's a battery situation install the bus bars as per normal and measure the voltage drop via direct contact on the battery terminal.

 

[Bob B]

I agree with @gnubie .... You would need a micro ohm meter to measure any resistance difference ....(There has been a couple of times lately that I wished I had one of these) .... but, if you do a high amp draw you might be able to compare voltage drop. Even then, I think it will be a very small number.

Checking the temperature of the bar with an IR thermometer would be another way .... but to do a good test, ambient temperature and load would have to be the same. Again, it would require a high load.

 

[HRTKD]

IF using 280AH EVE cells and you want to make up your own Busbars or have bar stock cut to size. LIKELY DOES NOT APPLY TO OTHER BRANDS.
IF making a BLOCK PACK the cross over busbar needs to be 4.250" long.
IF just building a Straight S Pack (in series only) the bar legths should be 3.750" long.

I get the 110 Copper pre-cut to size for easy, simplicity & consistency... Uniformity is a good thing in electrical tinkering.

Thanks for the recommendation on length. I will be cutting my own as I already have the bar stock. I have the right blade (Diablo non-ferrous) for my chop saw. Repeated cuts at the same length is a breeze. I'm used to that. Using my Wilton drill press vice, repeated, predictable holes won't be a problem there either. They'll all be right or they'll all be wrong.

The question now is, which thickness of aluminum bar do I use? .125 or .375? The .125 is the same thickness as three of the Xuba bus bars.

 

[ArthurEld]

Thanks for the recommendation on length. I will be cutting my own as I already have the bar stock. I have the right blade (Diablo non-ferrous) for my chop saw. Repeated cuts at the same length is a breeze. I'm used to that. Using my Wilton drill press vice, repeated, predictable holes won't be a problem there either. They'll all be right or they'll all be wrong.

The question now is, which thickness of aluminum bar do I use? .125 or .375? The .125 is the same thickness as three of the Xuba bus bars.

Now you just need to buy a countersink.
You should be able to look up what thickness to use. .125 x .75 copper is good for over 200A.
I doubt I'll ever get to 50A
The charts I found for aluminum start at 1/4 X 1.0 and they are good for over 300A.

 

[ArthurEld]

IF using 280AH EVE cells and you want to make up your own Busbars or have bar stock cut to size. LIKELY DOES NOT APPLY TO OTHER BRANDS.
IF making a BLOCK PACK the cross over busbar needs to be 4.250" long.
IF just building a Straight S Pack (in series only) the bar legths should be 3.750" long.

I get the 110 Copper pre-cut to size for easy, simplicity & consistency... Uniformity is a good thing in electrical tinkering.

Did you get the holes and chamfers too? We need a link to cheap custom China busbars

 

[HRTKD]

Now you just need to buy a countersink.
You should be able to look up what thickness to use. .125 x .75 copper is good for over 200A.
I doubt I'll ever get to 50A
The charts I found for aluminum start at 1/4 X 1.0 and they are good for over 300A.

To do the countersink, I can use a larger drill bit and limit the depth. On a drill press that's easy. I have a couple of step bits that would probably work too. As soft as aluminum is, my wood chamfering bits might work (for a while). Or, I can just buy some metal chamfering/countersink bits. I rarely pass up an opportunity to buy a tool.

 

[ArthurEld]

To do the countersink, I can use a larger drill bit and limit the depth. On a drill press that's easy. I have a couple of step bits that would probably work too. As soft as aluminum is, my wood chamfering bits might work (for a while). Or, I can just buy some metal chamfering/countersink bits. I rarely pass up an opportunity to buy a tool.

It can be done with a knife. A wood countnersink might work. A drill will work if it's short. You can cut off a drill or endmill and shape it into a countersink. But if you want the tool for the job, this will work - https://www.homedepot.com/p/Drill-A...ink-Bit-with-3-Flutes-DEWCSK1-2-120/310556137

 

[Steve_S]

LOL, buy another bit for countersinking holes... a bigger bit is just as good, simple and no extra cost (we all have lot's a bits).

 

[Zil]

I used a step bit. Use kerosene or mineral oil as cutting fluid. Put bar on battery. Run some load through bar. Use voltmeter lead on one terminal, other lead on opposite terminal. Measure voltage drop. The more current the more obvious the voltage drop. But, you don't need stressful current or time to overheat anything. Easily compare different buss bars in a few minutes.

 

[Craig]

I would take a new bus bar and an old bus bar connect each of them into the negative line the same way you would use a shunt. Attach a large load and measure voltage drop from one connection to another. Basically use bus bar as a, shunt. With a high load any multimeter with a mv resolution should give an idea.