Any issue connecting 4AWG cable to bus like this?

[wheelman55]

NOOB. OK. I did a bit more research on the busbar topic.

Build your own I’ve included

1. A link to a 0.25 inch x 3 inch rectangular tinned 110 copper bar.
2. A link to a copper ampacity

Tinned Copper bar material

Copper bar ampacity chart

Copper bar ampacity

With this you’ll be able to build a nice 1/4” x 3” 1,000 amp busbar to your specs.

Enjoy!

 

[rhino]

Because if I don't use those #10 screws, I will have to buy all new bus bars when I add the second MPPT. And this is the biggest bus bar I could find with 12 terminals.

I don't understand why would have to do that? Not only could you use the bolts that your fuses are connected to already you can at least double up on each bolt (you flip one lug upside down and add other lug right side up). That's why those bolts are so long to begin with so that you can double and triple stack lugs on them.

 

[AlaskanNoob]

I don't understand why would have to do that? Not only could you use the bolts that your fuses are connected to already you can at least double up on each bolt (you flip one lug upside down and add other lug right side up). That's why those bolts are so long to begin with so that you can double and triple stack lugs on them.

So you're saying I can put two lugs on a single stud? Well that certainly changes things! Is there a photo of this being done with the kind of lugs our 4AWG cables have?

 

[rhino]

So you're saying I can put two lugs on a single stud? Well that certainly changes things!

Look right on the Blue Seas page itself in FAQ section for that PowerBar:

 

[Tomthumb62]

It is best practice and more efficient to cluster your heavy outputs and inputs together towards the center of a busbar so it doesn't have to travel through much of the busbar needlessly generating heat.

Can you explain this? I would think that if 200A need to travel, traveling a longer distance will allow the heat to be spread over a bigger piece of bus bar, if the big wires are attached at the far ends from each other. Battery on one end and inverter on the other. If they’re right next to each other, that heat is going to get absorbed into a much smaller piece of bus bar.

 

[AlaskanNoob]

Look right on the Blue Seas page itself in FAQ section for that PowerBar:
View attachment 165980

Just saw this thread too.

Busbar stacking wires question?

If I have a busbar with 6 lugs but have to connect 8 wires to it, can you put 2 wires on a single lug? Of course the busbar would be rated to handle maximum amp load of the system.

diysolarforum.com

I thought the idea was to get as much surface area from the lug onto the bus bar, never would have thought stacking a lug on top of a lug would be okay.

Well this opens things up a bit. Many thanks!

 

[AlaskanNoob]

Can you explain this? I would think that if 200A need to travel, traveling a longer distance will allow the heat to be spread over a bigger piece of bus bar, if the big wires are attached at the far ends from each other. Battery on one end and inverter on the other. If they’re right next to each other, that heat is going to get absorbed into a much smaller piece of bus bar.

I think the idea is that the more metal it has to travel through is more resistance thus more heat.

 

[rhino]

I thought the idea was to get as much surface area from the lug onto the bus bar, never would have thought stacking a lug on top of a lug would be okay.

If for instance you have your largest "load" and largest power source on the same stud it wouldn't even need to travel through the busbar at all.

 

[AlaskanNoob]

If for instance you have your largest "load" and largest power source on the same stud it wouldn't even need to travel through the busbar at all.

I think I'd double stack the batteries only. So one battery might get less amps due to the longer travel of the power, but since I'm wiring each battery into the bus individually and not wiring them together, I don't think it matters for balance reasons.

 

[chrisski]

I think I'd double stack the batteries only. So one battery might get less amps due to the longer travel of the power, but since I'm wiring each battery into the bus individually and not wiring them together, I don't think it matters for balance reasons.

You think one battery getting less amps makes a difference in balancing?

What happens when you pull a large load? Will it matter that one battery is providing 30% more power under load?

I spent a lot of time making sure my battery cables were the exact same length. At 50% inverter load, I was within 3% output for each of my two batteries; at 10% inverter load, it changed to 8%.

 

[TomC4306]

Maybe just replace the Phillips screws with an appropriate hex head machine bolt with washer and lock washer.

Might make torqueing easier.

I love the hardware drawers at Home Depot and Lowe's.

 

[AlaskanNoob]

You think one battery getting less amps makes a difference in balancing?

What happens when you pull a large load? Will it matter that one battery is providing 30% more power under load?

I spent a lot of time making sure my battery cables were the exact same length. At 50% inverter load, I was within 3% output for each of my two batteries; at 10% inverter load, it changed to 8%.

I think that if you have batteries connected together in parallel, that you want the cables from each of them to the bus bar to have the same resistance so that they're both getting the same amps. The BMS can adjust, but it's best practice to ensure both are getting the same amps.

When you pull a large load, it should be split evenly among the batteries. So one battery should not be providing 30% more power under load.

I also think that modern BMS can account for these differences, so it likely won't make a difference.

In my case, with each battery individually wired into the bus bar (8 individual batteries), it wouldn't matter.

That's my understanding anyway. With zero experience, no education, and less than optimum research skills.

 

[AlaskanNoob]

Maybe just replace the Phillips screws with an appropriate hex head machine bolt with washer and lock washer.

Might make torqueing easier.

I love the hardware drawers at Home Depot and Lowe's.

I wonder what Sunshine_Eggo would think of your suggestion?

 

[sunshine_eggo]

I wonder what Sunshine_Ego would think of your suggestion?

LOL... I see what you did there. Cute.

Look up the torque spec on #8 and #10 threads.

Then look up the torque spec on the stud size for your lugs.

There's your answer.

 

[AlaskanNoob]

LOL... I see what you did there. Cute.

Look up the torque spec on #8 and #10 threads.

Then look up the torque spec on the stud size for your lugs.

There's your answer.

From what I can find after ten minutes of wading through the Internet, is that #10 fasteners (maybe that's not threads) have torque ratings as such:



And Blue Sea specs say 18 inch pounds for the #10.

As to the torque requirements for a 25-8 lug, or for the stud, I can't find anything. Haven't found it in Blue Seas documentation. I'm sure it's on the Internet somewhere but I've exhausted my fifteen minutes of trying to look through verbiage to find it.

 

[AlaskanNoob]

I don't understand why would have to do that? Not only could you use the bolts that your fuses are connected to already you can at least double up on each bolt (you flip one lug upside down and add other lug right side up). That's why those bolts are so long to begin with so that you can double and triple stack lugs on them.

So if the bus bar is toward the bottom in these photos, which one(s) of these are acceptable (I used a larger cable for the question rather than the 4AWG)?

A:


B:


C:


D:


Hopefully having some bend like in D would be okay because that lower bus bar is blocked by the upper bus bar.

 

[wheelman55]

The goal is for the lugs to lay flat against the busbar.

 

[400bird]

A, but with both wires hanging down, stacked right on top of each other.

I'd rather drill out and use larger bolts in place of some of the screws.

 

[AlaskanNoob]

A, but with both wires hanging down, stacked right on top of each other.

I'd rather drill out and use larger bolts in place of some of the screws.

Maybe it will not be so pronounced with 4AWG, but I would expect there to be a gap between the two lugs given the shape of them. They won't lay flat on top of each other I don't think, but I'll check it out tomorrow.

 

[AlaskanNoob]

The goal is for the lugs to lay flat against the busbar.

One lug will be flat against the busbar, and the other lug won't touch the busbar doing it this way. I'm guessing you mean one lug laying flat against the busbar and the other lug laying flat against that first lug? Which I think means the cables have to not be on top of each other (and best would be to do it like rhino said, with cable opposite direction).

As in picture A.