Bare Vs Tinned Vs Silver Copper Bus Bars

[teekay18]

I was hoping to get some information, thoughts and opinions on the pros and cons of bare vs tin vs silver copper for bus bars on aluminum post LFP cells and the corresponding appropriate lugs to be used with each.

I live in rural Northwestern Ontario so I plan on ordering copper bar stock online but I have 3 options to choose from.

I am trying to decide between:

0.25"×1" rectangle bar bare copper
Price: $71.03 per 72"

0.25"×1" full round edge silver flash copper
Price: $53.53 per 72"

0.25"×1" full round edge tinned copper
Price: $54.00 per 72"

I am building 3 different batteries, 24v 2p8s, 24v 8s and 12v 4s using 280ah 3.2v LFP cells from Xuba. None of the batteries will be in harsh climates or high humidity. I need 140 inches for the batteries themselves plus I want to make my own common bus bars so I am going to buy 3x 72" pieces because that's the cheapest length for shipping.

I was going to buy the silver flashed copper bar because it's the cheapest, but wanted to make sure there's no issues with using silver on aluminum posts.

If I use silver flash copper should I use bare copper lugs or tinned copper lugs? Can't really find any silver copper lugs.

I appreciate any kind of feedback or thoughts or opinions.

Thanks.

 

[Steve_S]

I purchased my copper bar stock from MetalPros in Ottawa and they shipped the product out quite fast. PayPal and Interact payments accepted.

Quote - Metal Pros

With my 280AH packs, I used
COPPER C110 FLAT BAR ASTM-B133 0.125" x 0.750"
For two 24V/280AH packs (8 cells),
CUTS: 2x 4.250" long, These are the Cross Bars across the back of the pack. The BusBars between the cells 12x 3.750 long.

They do not carry tinned copper stock but a dab of noalox / Ox-guard solves any corrosion potential (just a light dab will do).
Silver or silver plated is gonna cost and is not really worth looking at unless you want to spend cash.

Photo of my 24V/280AH pack assembly, if it helps. NB: I put heat-shrink wrap on the bars and that makes it a tad harder to see.

 

[teekay18]

Thanks for the advice Steve_S!

Will 0.125"×0.75" copper handle 250 amps?

What's the exact cell terminal diameter?

The 12v 4s 280ah could see a 250amp spike from the inverter, but I never plan to surge my inverter that high. Amp draw will be less than 167amps most of the time and the 24v batteries will only draw about 125 amps. I just thought since they are 280ah cells rated for 1C that I would use extra thick bus bars just to be on the safe side.

Would 0.125"×1" be big enough for my loads then?

 

[mrdavvv]

Hello @Steve_S

How do you apply the No-alox?. I guess just on the "outside" connection, but nothing between bussbar and battery post?.

Ive been thinking about it lately, for example this guys applies OXGARD between connections (After sanding them), but not sure if thats entirely correct...

Also heard of some people using stainless washers between battery / busbars to avoid galvanic corrosion from aluminum&copper.

 

[Steve_S]

I built my packs to handle 1C (280A).
The screw/bolt is M6 or 1/4" hole. I used a drill press with a little jig to make the holes (chamfered as well).
Bolts & washer's I used are stainless steel.

I used Ox-Guard actually, post drilling & chamfering, and putting on the shrinkwrap, I wiped down the copper (contact face) with Rubbing Alcohol and applied a wee dab of ox-guard, only on the surfaces that make contact. Just a very thin coating, no gobs or blobs.

 

[mrdavvv]

Interesting.

Let me see if i get it, you applied Oxgard in all the "interface" between bussbar and battery right?... the bolt thread, and the surface between battery post and busbar?

Any idea if the original bolts from Xuba are stainless?, for me they look galvanized but not sure.

Ill never be brave enough to drill press my batteries

 

[Steve_S]

Drill press was used on the copper stock, not the batteries, oh my....
Screws from Xuba were stainless.
Ox-guard only applied to contact faces on Busbars & Cell posts, not screws or other.

 

[mrdavvv]

Drill press was used on the copper stock, not the batteries, oh my....
Screws from Xuba were stainless.
Ox-guard only applied to contact faces on Busbars & Cell posts, not screws or other.

Haha, well ive seem some people doing it when they want a bigger thread size, or when they ruin the connection... seems very risky!.

Got it!, ill get some compound for my batteries.

 

[nosys70]

tinned copper is the best, it keeps copper from oxydizing and tin is a soft metal that allows for better contact.
but you should choose chemically tinned plate, since the tin layer is very thin and tin is not a particularly good conductor.
you can easily chemically plate with zinc or tin. It is just a matter of immmersing the both ends of the bus bar in a liquid for a few minutes.
Silver is nice for conductivity but it oxidize also very fast so not sure it will last as long as tin.

 

[mapguy525]

Online Metals has bare and tinned copper bar. They have a 20% off promotion today.
https://www.onlinemetals.com/en/buy/copper-full-round-edge-110-h02-tinned

 

[teekay18]

Online Metals is where I was looking because of the 20% off today, but I live in Canada on the US border, but I can't cross the border right now to pick stuff up, so I have to get it shipped to Canada which is expensive and very slow right now.

Steve_S provided a good source for Canada. They replied with a quote very quickly. So I think I am going to go with them.

 

[Steve_S]

Online Metals is where I was looking because of the 20% off today, but I live in Canada on the US border, but I can't cross the border right now to pick stuff up, so I have to get it shipped to Canada which is expensive and very slow right now.

Steve_S provided a good source for Canada. They replied with a quote very quickly. So I think I am going to go with them.

The folks at metalpros are really great and they are fast too. The pricing is in Canadian Dollars not US$ so it looks higher priced to them.
They can get custom / specialised stuff too but you have to call them for that. If they can get you Tin Plated Copper bar stock it may be worth the few extra sous.

 

[teekay18]

The folks at metalpros are really great and they are fast too. The pricing is in Canadian Dollars not US$ so it looks higher priced to them.
They can get custom / specialised stuff too but you have to call them for that. If they can get you Tin Plated Copper bar stock it may be worth the few extra sous.

I agree, the folks at Metalpros are top notch. I must have exchanged emails back and forth 5 times today, I wish all retailers communicated this way.

They were able to order in 0.25"×1" COPPER C110 FLAT BAR ROUND EDGE ASTM-B133 PRE TINNED, so I pulled the trigger on an order.

2-3 day lead time to bring in. I paid $240.30 + $47 shipping + $8 for cuts for a total of $333.69 with tax for 18' of it in 6x 36" pieces. It was an extra $52 to get tinned and only an extra $82 to get 0.25" vs 0.125" because of the 25% discount on the 0.25" vs 15% only for 0.125".

But I think I am going to figure out all my pieces and get them to cut them all for me. I think it's worth paying them an extra $30 to save me from making 30-40 repeated cuts myself.

Did they do a nice job of cutting your pieces Steve_S?

 

[Steve_S]

The cuts were millimeter accurate (you may have to clean up the edges a tad)
I suggest using the BusBars that were sent as a template to mark the holes. I made a little jig from scrap wood on the drill press and that made drilling the holes evenly much easier and a boat load quicker.

 

[teekay18]

Glad to hear.
I was already envisioning a wooden jig setup on the drill press to make drilling easier, good tip!

 

[Hydroselator]

Hello @Steve_S

How do you apply the No-alox?. I guess just on the "outside" connection, but nothing between bussbar and battery post?.

Ive been thinking about it lately, for example this guys applies OXGARD between connections (After sanding them), but not sure if thats entirely correct...

Also heard of some people using stainless washers between battery / busbars to avoid galvanic corrosion from aluminum&copper.

I would caution against stainless against aluminum. On aluminum aircraft pressure skins (2024 series Al) with 401 stainless doublers installed wet with sealant and all surfaces primed we always see severe corrosion on the aluminum after several years when the stainless doublers are removed.

 

[HRTKD]

I would caution against stainless against aluminum. On aluminum aircraft pressure skins (2024 series Al) with 401 stainless doublers installed wet with sealant and all surfaces primed we always see severe corrosion on the aluminum after several years when the stainless doublers are removed.

I'm glad you called that out. I read that post and then kept expecting someone to say something. Adding to what you said, corrosion is just one problem with putting a stainless steel washer between the battery and the bus bar. Stainless steel is a less than ideal conductor.

 

[mrdavvv]

Thanks for the heads up guys.

I want to understand the same situation applied to PV aplications:

There is a general recommendation on solar panel framing to put some kind of stainless steel "interface" between the ground cabling and the aluminum frame that support the panels... that i believe its done to avoid galvanic corrosion. If im correct, galvanic corrosion its the degradation of materials by the current produced between dissimilar metals. I have found this in some solar panel manuals and recommendations.

Why it could be recomended to do this mix of stainless and aluminum in this situation, and not in batteries?

I have probably a lot of misconceptions on this post, but hopefully someone can help me clarify this!

 

[Zil]

0.25 that is 1/4 inch. That is much too thick. But each their own. But one thing caught my attention; never have a washer between the battery and wire lug. A washer can be used between lug and nut or bolt head, but never between lug and battery. Back to 1/4 x 1 inch copper. Equivalent to 1 1/2 times 4/0 cable, plus a bit more. I use 1/8 x 1 inch copper. I use a torch and "tinners flux" to give it a good tin plating that resists corrosion. On aluminum I would coat with Sanchem Inc NO-OX "A SPECIAL" for protection. Between the lugs and battery terminal and over the out side after torqued.

 

[schmism]

were does squished copper pipe fall in for buss bar material.