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direct mounted busbars connecting five packs?

@Ampster, I consider myself pretty much a noob. I'm no expert and not embarassed to say it.

When it comes to choosing something like wiring or busbars, when in doubt I rely on the experts on this forum.

But I can say that I would not be relying on advice from someone who's posting history has multiple references to using aluminum wire, miscalculating the ampacity of their application, and almost starting a fire or shorting their system because the wire or the wire insulation melted.

That's just me. Not saying you're not generally right or judging beyond that. Just saying I wouldn't trust your advice for my own system. Mainly, because I can't afford to burn down my house on account of an error.
 
kolek said:
When it comes to choosing something like wiring or busbars, when in doubt I rely on the experts on this forum.
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That is a good approach until you acquire the knowledge and skills of those experts. I am not arguing for Aluminum or trying to change your mind. I just want other readers who may have some desire think for themselves to understand the pros and cons so they can make the optimal decision for their application.
 
@Ampster So basically, you like the OP's idea? A couple of long exposed aluminum bars on the front of a large battery bank like that seem like a smarter idea to you than a more traditional set of insulated copper wires?
 
kolek said:
Yep. They're wrong. Otherwise why is everyone using copper busbars and wiring?
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In the industrial market, they aren't. If you see transmission cables out in the open they're aluminum. That was the whole point of the @Ampster post.
And in the DIY market, anyone that deals with prismatic LFP cells has aluminum terminals on those cells, so the advice on coating to prevent oxidation seems pertinent to our applications.
kolek said:
@Ampster So basically, you like the OP's idea? A couple of long exposed aluminum bars on the front of a large battery bank like that seem like a smarter idea to you than a more traditional set of insulated copper wires?
Click to expand...
@Ampster never said either of these things. Don't put words in someone else's mouth just to start an argument.

The Ignore feature on this site comes in handy once again.
 
kolek said:
So basically, you like the OP's idea?
Click to expand...
I did not say that. I made it clear that Aluminum has an important role in the world of electrical distribution. Whether the busbars are Aluminum or Copper has no bearing on the danger of them being exposed. Both could be covered by shrink tubing or plexiglass. I came close to using Aluminum busbars because of the availability and cost. Ultimatlly I chose Copper for my 3P16S pack because with six connections on each busbar the flexibility of copper was going to compensate for any differences in the six connected aluminum terminal tops. I used anti oxident because of the difference between the terminal tops and busbar materials.
However, if you continue to put words in my mouth or misinterpret what I am saying, I will take the suggestion of @LakeHouse and use the Ignore button, This dialogue has progressed beyond being a useful discussion for the benefit of other readers.
 
What I was suggesting was to make a copper bus bar yourself. Use wires to connect the battery terminals to the bus bars. The slack in the wires lets things move a bit.

Attaching bus bar directly to the top of the battery posts is asking for trouble in terms of making and maintaining good contact. A little shift here and there and your contact will get worse over time. Might be years and might be months.

Look over in the DIY battery section of the forum to see how folks do those. They have a bump in the middle to allow for a little movement.

Aluminum expands and contracts more than copper and requires an even larger bus bar to carry the current safely.

Maybe I should turn it around and ask - what is it you are hoping to gain by mounting the bus bars directly to the top of the batteries regardless of material?
 
Ampster said:
I am not sure I understand your math? That scenerio would be a dead short and I presume the OP will have an overcurrent device of less than 500 Amps. He mentioned that his inverter is 12kW which at 50 volts is 240 Amps.
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My math was done prior to his mentioning the inverter he was using. At that point all I had to go on was 5 batteries capable of outputting 100amps each - so - 500amps.
 
robbob2112 said:
Maybe I should turn it around and ask - what is it you are hoping to gain by mounting the bus bars directly to the top of the batteries regardless of material?
Click to expand...
I think the OP stated explicitly that the main rationale was to save money over the cost of using regular copper wire connects. I also think he's planning to implement his idea regardless. OP feel free to correct me if I'm wrong.
 
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Ampster said:
However, if you continue to put words in my mouth
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What words did I put in your mouth? Please copy and paste them in your response. If you're just spouting nonsense as you appear to be, I'm reporting you to the moderator.
 
since the terminals of the mounted to the box using a plastic fixtures, and the plastic allows for some deformation, wouldn't that eliminate the worry of rigidity of the aluminum? any slight angle difference should be self-correcting when the terminal bolt is torqued down and the plastic allows the terminal to adjust. correct?
you can visually see the plastic deform slightly when the bolts are tightened to mount the terminal to the case, so i would think the terminal would be allowed the same give.
 
There are positive and negative arguments for using aluminum bar stock to make connections between batteries. I purchased a couple different sizes of aluminum bar stock to use as bus bars between the cells. My main reason for doing so was that it would be an aluminum to aluminum interface, less likely to corrode. But as Ampster stated, anti-oxident coatings reduce the concern about corrosion, especially between disparate metals.

Properly sized, I would have no issue with using aluminum bar stock as the OP has asked about. For the same amperage, copper would be smaller. Instead of using the aluminum bar stock I had on hand, I used copper bar stock to make short connections between components.

The various flavors of aluminum alloys have different ratings. 6061 is not the most conductive of aluminum alloys.

kolek said:
What words did I put in your mouth? Please copy and paste them in your response. If you're just spouting nonsense as you appear to be, I'm reporting you to the moderator.
Click to expand...

The moderator is watching. Making a personal attack (saying someone is "spouting nonsense") is more likely to get YOU in trouble.
 
robbob2112 said:
What I was suggesting was to make a copper bus bar yourself. Use wires to connect the battery terminals to the bus bars. The slack in the wires lets things move a bit.

Attaching bus bar directly to the top of the battery posts is asking for trouble in terms of making and maintaining good contact. A little shift here and there and your contact will get worse over time. Might be years and might be months.

Look over in the DIY battery section of the forum to see how folks do those. They have a bump in the middle to allow for a little movement.

Aluminum expands and contracts more than copper and requires an even larger bus bar to carry the current safely.

Maybe I should turn it around and ask - what is it you are hoping to gain by mounting the bus bars directly to the top of the batteries regardless of material?
Click to expand...
the bars would be mounted on the front face as the batteries are vertically stacked, and locked into place, so very little opportunity to shift. although i do acknowledge that it could be a possible point of failure.

the possible gain is a much simpler design, less possible points of possible failure, etc.
thats assuming everything would work and play nicely
 
stacks said:
since the terminals of the mounted to the box using a plastic fixtures, and the plastic allows for some deformation, wouldn't that eliminate the worry of rigidity of the aluminum? any slight angle difference should be self-correcting when the terminal bolt is torqued down and the plastic allows the terminal to adjust. correct?
you can visually see the plastic deform slightly when the bolts are tightened to mount the terminal to the case, so i would think the terminal would be allowed the same give.
Click to expand...

I would be reluctant to rely on the plastic fixture to take up any differences there might be in making proper connections. In a mobile environment, using bar stock to make the connections between rack batteries isn't ideal, in my opinion. In a non-mobile environment, probably not a big deal. My existing cells are joined by sold busbars, not the flexible bus bars. The cells are then held in a compression fixture to ensure that the cells don't move. They've been in place since 2020 in my RV camper which has seen some rather rough roads.. I check the fasteners once a year and they have all been in good shape.

The idea you have to use aluminum bar stock is good in that it reduces three points of contact (lug->cable->lug->terminal) to one, depending on how you count the points of contact. The cable will allow some flexibility, but a poorly constructed cable with crimped lugs can introduce contact issues if the two lugs are not oriented in the same plane.

When I make a cable, one lug gets crimped on then I soft mount the lug on the other end, place the cable in place to get the lug oriented in the proper plane and then crimp the second lug on.
 
stacks said:
since the terminals of the mounted to the box using a plastic fixtures, and the plastic allows for some deformation, wouldn't that eliminate the worry of rigidity of the aluminum? any slight angle difference should be self-correcting when the terminal bolt is torqued down and the plastic allows the terminal to adjust. correct?
you can visually see the plastic deform slightly when the bolts are tightened to mount the terminal to the case, so i would think the terminal would be allowed the same give.
Click to expand...
This would reduce some of the worry of rigidity, yes. And in that respect, aluminum wouldn't be much different from copper, other than the very slightly larger coefficient of thermal expansion.

I think there are two issues with what you're proposing and I have different concerns with each of them:
1. Aluminum Bus Bars - Good electrical contact could be a problem, as noted earlier. They need to have a larger cross-section, which isn't necessarily a problem and could actually be a good thing in some cases.
2. Solid bus bars bolted directly to battery terminals - Possibly problematic thermal growth, very good alignment required for proper fit-up, danger of large exposed bus bars (which you recognize and seem to have under control). Also lack of ability to change out or remove a battery while the system is operating, which I hadn't thought of until just now.

In the end it is of course up to you to decide what you're going to do. Personally, I wouldn't go with solid-aluminum bus bars bolted directly to terminals.
 
robbob2112 said:
At that point all I had to go on was 5 batteries capable of outputting 100amps each - so - 500amps.
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I understand your assumption. I still don't understand what load you assumed was going to make those busbars "red hot"? My understanding of .5 x 2.0 Aluminum is that it can carry 800 Amps. As I also mentioned, I had asssumed the overcurrent protection would be sized to prevent over discharge of the batteries.
Just to be clear I am not in favor of exposed busbars either.
 
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I personally don't see any problem with the aluminum bus bar it seems plenty overkill for the situation. I would be more concerned with them being directly mounted to the battery in the case of an internal failure (Shorted fet, BMS failure, or any B-box wiring short) in one of the batteries there is no easy way to disconnect/isolate.

Just food for thought.
 
Copper, aluminum either will work fine if sized correctly, I would only do it if I could protect the buss bars so I didn’t kill a family member or other bystander and had good fuse protection in each battery box, I wouldn’t want four batteries shorting into a fifth.

I am putting together 12-304ah box kits going buss bars and DLO cable, easier to isolate and remove a battery if needed without disassembling the entire battery bank.
 
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