Using aluminum lugs on 280Ah terminals

fafrd

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I saw these standard aluminum lugs at Hime Depot and asked myself if there is any reason I could not use these for the first - connection to the BMS (B-) as well as the final + connection to the fuse: https://www.homedepot.com/p/Commerc...-Rated-Mechanical-Lug-2-Pack-G99002/310741850

And now that there is all of this focus on flexible busbars, I’m asking myself whether these could work for all busbar connections (replacing solid busbars with short lengths of whatever AWG cable)?

Finally, not that we seem to be moving to welded terminals at least for 280Ah cells, I’m wondering whether welding on aluminum lugs might prove to be an effective and low-cost solution?

Thoughts from anyone who has used these aluminum lugs for DC battery-based applications - is there an issue with these Aluminum-Lugs-to-Bare-Copper-Wire connections that I’m overlooking?

Heck, with these you could even use aluminum wire eliminating any possibility of galvanic corrosion...
 

HRTKD

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If there is any concern about humidity or salt in the air (marine), then a closed end lug with heat shrink tubing (with adhesive) is called for. There's no way to seal the cable with that type of lug.
 

fafrd

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If there is any concern about humidity or salt in the air (marine), then a closed end lug with heat shrink tubing (with adhesive) is called for. There's no way to seal the cable with that type of lug.
Understand.

But for stationary use in a dry non-marine environment, what do you think if the idea?
 

HRTKD

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If it was a solid wire, that would work OK. The verbiage in the HD page makes it sound like this is intended for AC, not DC, which would be a solid wire, not stranded.
 

fafrd

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My battery will be stationary in the basement and I’m likely going to house it in a sealed temperature-controlled box.

I was hoping to use my solid busbars but I’m now getting concerned I need a flexible busbar solution to maintain reliable mechanical/electrical connection in the face of expansion/cell deformation through charge cycling.

Building short copper cables with cold-welded lugs is one solution but pricey.

braided busbars is another solution but even pricier since I’ll need to double-up at my current levels.

CALB Omega-shaped copper busbars may be another solution I have not priced out yet.

So if this Aluminum-Lug with Aluminum or copper wire is another viable option for my use-case, I’ll price it out...
 

fafrd

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If it was a solid wire, that would work OK. The verbiage in the HD page makes it sound like this is intended for AC, not DC, which would be a solid wire, not stranded.

Well, that could be an issue. If these lugs are only rated for high DC current with solid wire, that may eliminate all of the flexibility that motivated the idea to start with...

Do you know if they make Aluminum Lugs like this rated to carry high DC Amps through stranded wire?
 

HRTKD

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If this is a stationary implementation and you have a solid compression frame, solid bus bars should work just fine.

I'm not in a stationary environment but have a compression frame that I'm confident in. Solid bus bars are working fine. I've got over 2000 miles on my solution in just the past 6 months. 50 miles of that is poorly maintained dirt roads. The rest of it is poorly maintained paved roads. :)
 

fafrd

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If this is a stationary implementation and you have a solid compression frame, solid bus bars should work just fine.

I'm not in a stationary environment but have a compression frame that I'm confident in. Solid bus bars are working fine. I've got over 2000 miles on my solution in just the past 6 months. 50 miles of that is poorly maintained dirt roads. The rest of it is poorly maintained paved roads. :)
Would be interested to know what solution you used for your compression frame - is it written up somewhere?

A fallback I’m considering is to build my 8S battery at 100% SOC and tighten my solid busbars down there, then don’t worry about compression or lost potential cycle life as my cells shrink when discharged.

If you’ve got a way to maintain some compression without causing any concern with stress or movement of the busbars, I’m interested.

Even in that case, though, I’m still interested in whether the aluminum lugs with set screws into copper or aluminum wires are an option for the - connection into the first cell and the + connection out of the last cell...

I found some similar aluminum lugs rated for AC/DC amps, so they do exist but I’m not sure if cost yet nor whether that DC rating is only with solid wire.
 

Hedges

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If it was a solid wire, that would work OK. The verbiage in the HD page makes it sound like this is intended for AC, not DC, which would be a solid wire, not stranded.

AC/DC, solid/stranded ... what's the difference?
I don't believe any of that matters to electrons flowing in a conductor. Maybe, just maybe, flowing across a dissimilar metal interface.

The DC lugs in my inverter don't seem functionally or material-wise different from the AC lugs in my breaker panels.
 

HRTKD

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AC/DC, solid/stranded ... what's the difference?
I don't believe any of that matters to electrons flowing in a conductor. Maybe, just maybe, flowing across a dissimilar metal interface.

The DC lugs in my inverter don't seem functionally or material-wise different from the AC lugs in my breaker panels.

Wire with lots of fine strands tends to not work well in screw down terminals. At least not for me. A workaround for that is to use a ferrule.

The HD webpage doesn't provide an amp rating. Absent that, I wouldn't use it.
 

HRTKD

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Would be interested to know what solution you used for your compression frame - is it written up somewhere?

A fallback I’m considering is to build my 8S battery at 100% SOC and tighten my solid busbars down there, then don’t worry about compression or lost potential cycle life as my cells shrink when discharged.

If you’ve got a way to maintain some compression without causing any concern with stress or movement of the busbars, I’m interested.

Even in that case, though, I’m still interested in whether the aluminum lugs with set screws into copper or aluminum wires are an option for the - connection into the first cell and the + connection out of the last cell...

I found some similar aluminum lugs rated for AC/DC amps, so they do exist but I’m not sure if cost yet nor whether that DC rating is only with solid wire.

3/4" plywood ends and four 1/4" threaded rods to hold them together. My compression frame was assembled at 100% SOC, though that was by accident. If I had thought about it, I might have done it at a lower SOC. However, since my cells were clamped during the top balance and there was no observed (using Mark I eyeball) expansion, it's probably a wash.

If the cells do shrink when discharged, that could put some stress on the terminals. But probably not. I would still put something in place to hold the cells.
 

fafrd

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3/4" plywood ends and four 1/4" threaded rods to hold them together. My compression frame was assembled at 100% SOC, though that was by accident. If I had thought about it, I might have done it at a lower SOC. However, since my cells were clamped during the top balance and there was no observed (using Mark I eyeball) expansion, it's probably a wash.

If the cells do shrink when discharged, that could put some stress on the terminals. But probably not. I would still put something in place to hold the cells.
Exactly the same as the small compression jig I threw together for capacity testing single cells...

If you build a relatively rigid / non-flexible structure at 100% SOC you should have little/no movement as you discharge to 0% SOC. Cells should shrink and open up some space between them, there will be little/no compression force on the cells most of the time (meaning you may get only 2500 cycles rather than 3500), but there should be zero stress on your busbars or terminals.

I’m thinking about going exactly this way and prioritizing reliability of mechanical/electrical connections over an attempt to extend cycle life...

If you have not yet done so, attempt to slide a piece of paper between cells next time you are at 0% SOC or whatever lowest discharge you get to - you ought to be able to confirm that your cells are no longer in contact and are free-standing..,
 

fafrd

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Wire with lots of fine strands tends to not work well in screw down terminals. At least not for me. A workaround for that is to use a ferrule.

The HD webpage doesn't provide an amp rating. Absent that, I wouldn't use it.
Well there is solid, there is fine-stranded (is: welding wire) and there is stranded (few large strands).

I can see that those lugs are not intended for use with fine stranded wire but I’ve had no difficulty using them with standard stranded wire (including 4/0 stranded aluminum wire).

Once you get into needing to use ferrules, any cost advantage of using standard wire has gone out the window and the only possible advantage of using this class of lug is that is can be permanently installed and disassembly can be achieved using the set screws...
 

HRTKD

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All my cable in my system, except for the PV cable, is welding cable. All my terminations that don't use a cable lug are using a ferrule. The largest ferrule I'm using so far is 6 awg. I bought some 1 awg ferrules but I don't have a tool to crimp it.
 

fafrd

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Well after pricing out how much it would cost to make 7 flexible 2/0AWG busbars from 14 2/0 plated lugs ($14) and 2 feet of 2/0 welders cable ($6), I’m forgetting this idea about using setscrew-type Aluminum lugs.

I can afford the spend $20 on 7 flexible 2/0AWG ‘busbars’ that can handle currents of up to 280A...

These Aluminum set-screw type lugs still might be something for the latest-and-greatest ‘welded terminal’ crowd to consider, but for those of us with threaded terminals (the majority of which are hopefully using grubscrews), these end up being more expensive than plated lugs and may not offer the same compatibility with flexible welder’s cable.

Mow that it looks like I’ll have an acceptable solution to the ‘flexible busbar’ problem, I may even go back to planning to compress my cells in a ~300kgf fixture...
 

Mike Jordan

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If it was a solid wire, that would work OK. The verbiage in the HD page makes it sound like this is intended for AC, not DC, which would be a solid wire, not stranded.
Solid wire just because its A/C?!? Wait.... waAat?!?
 

Mike Jordan

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Hey, if you haven't seen 2 awg AC wire, just wander through the electric aisle at HD.

I already explained above why a fine stranded wire isn't great for that kind of terminal.
I look at electrical panels all day every day. Its what I do. I've never seen a solid 2 awg wire. It would be impossible to bend and the heat expansion and contraction would bust itself out of the lug. Stranded 2 awg goes into those type of lugs all of the time
 

fafrd

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I look at electrical panels all day every day. Its what I do. I've never seen a solid 2 awg wire. It would be impossible to bend and the heat expansion and contraction would bust itself out of the lug. Stranded 2 awg goes into those type of lugs all of the time
Yes, but not welding wire...
 
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