Best Practices For DIY Battery Connections

[aaron_c]

I'm gathering the stuff to put my battery bank together. I've got the 280 AH LiFePO4 cells sold through @Michael B Caro, and that includes enough tinned copper bussbars to almost cover all the connections if I double them up (I need to double them up so I get enough amperage). The right-angle bussbar will be made of copper bar I ordered.

The stainless nuts and bolts included with the kit are too short for me to feel confident using them with doubled-up bussbars. And it seems the consensus is that the best way to DIY this is to insert a grub screw (aka "set screw") into the battery terminals, attach the screw with loctite or something similar, and then bolt down the bussbars over the set screw. In other words, I'd use a set screw instead of a regular hex bolt or whatever.

So far so good. But now enters galvanic corrosion, and the prescribed solutions seem to depend on a) how wet and how salty the environment is b) how long one expects the battery to last and c) how well the temperature will be controlled in the battery housing. And I haven't seen any explicit explanation for my situation. Which is:

a) not salty (not a marine application) and not wet (will mostly be in dry environments),
b) hoping for a lifespan of 15-20 years or so (in other words I might not use the battery every day, think "RV")
c) very little temperature stability (no air conditioning and minimal use of a heater)

So. Generally speaking I'm under the impression that I could either use aluminum or stainless steel grub screws, and aluminum or stainless steel washers and nuts for that screw. And I'm under the impression that in either case I should first clean off the surface of the aluminum battery terminals with maybe a nail file and then apply...shit, I can't see what I ordered, but I think it was Ox-Gard. And I gather I should re-apply the ox-gard on at least the battery terminals every six months or so.

But what I'm not clear on is whether I should be using aluminum or stainless steel grub screws / nuts / washers / lock washers. Would stainless grub screws attached with red loctite corrode the aluminum inside the terminals in that 15-20 year period?

Thanks!

 

[svetz]

You want the metals to be non-reactive with each other to prevent corrosion.

I'm not sure what would be best in your case (hopefully others will), but know that aluminum and stainless steel are a bad combination, see: https://www.albanycountyfasteners.com/blog/stainless-steel-and-aluminum/

 

[Steve_S]

Brass or Stainless grub screws will do perfectly.
Serrated washers hold better than lock washers.
No-Alox / Ox-Guard only has to be applied ONCE and only a very slight amount, do not get on screw / nut threads.
Yes, ensure the contact surfaces on the cells & busbars are Clean and free of greases, waxes or anything, other than a very light coating of oxguard once cleaned up.
* Enure you have no ridges or burrs on the busbars where the holes are. Very common cause of issues. Even Vendor supplied factory busbars which are stamped have a slight ridge from the stamping process.

Loctite CAN present issues it does not pass electricity. Only use a tiny drop on the but thread if you must use it. See serrated washers.
Worst case scenario, double the nuts and forget it forever.

 

[aaron_c]

Brass or Stainless grub screws will do perfectly.

Great, that makes things simpler!

Serrated washers hold better than lock washers.

Thanks. Hah, to me serrated washers are a kind of lock washer, "toothed lock washers" to be exact. Which I was planning on using. Probably should have been more precise

No-Alox / Ox-Guard only has to be applied ONCE and only a very slight amount, do not get on screw / nut threads.

Once again this is great and makes my life much simpler.

Yes, ensure the contact surfaces on the cells & busbars are Clean and free of greases, waxes or anything, other than a very light coating of oxguard once cleaned up.
* Enure you have no ridges or burrs on the busbars where the holes are. Very common cause of issues. Even Vendor supplied factory busbars which are stamped have a slight ridge from the stamping process.

OK, so from this my understanding of how I should be fixing the bussbars goes like this. Let me know what you think!

1) Metal File (Coarse): The metal file is to file down any ridges or burrs on the bussbars. This is to be done very carefully so I don't file off the tin coating (except, of course, where the tin coating is part of a burr or ridge)

2) Metal File (Fine): This might actually just be a nail file because that's the finest file I have on hand. Again, to help remove waxes and burrs and just bits of metal that aren't as flat as they could be. Again, being careful to not remove the tin coating if possible.

3) Soap and Water: To remove grease, mostly. Dry with a microfiber cloth immediately after washing with soap and water.

4) Vinegar and Baking Soda: So I *think* this only applies to my single copper bussbar that's not tin-coated. I think the tinned bussbars (the ones that came with the cells) should be fine...right? Anyhow, for the copper bussbar I looked up how to remove oxidation from copper and this is what wikihowto said: 3 parts baking soda to one part vinegar as a paste, applied to the copper and left to sit for 10 minutes to an hour. Then I'd wipe it off with the microfiber cloth.

5) Put the bussbars on the batteries (with a light coat of Ox Gard on the battery terminal) and tighten it all down using the specified torque (I'd need to look that up in my inverter manual). I'm unclear whether I need to also add Ox Gard in between the doubled-up tinned copper buss bars.

What do you think?

Loctite CAN present issues it does not pass electricity. Only use a tiny drop on the but thread if you must use it. See serrated washers.
Worst case scenario, double the nuts and forget it forever.

I'm confused, I thought that we weren't relying on the posts to conduct electricity? But good to hear that the worst case scenario is, well, not too terrible.

 

[Steve_S]

All good, you have it nailed. Tech Tip: DAWN Dishsoap is a wonderful degreaser and does not leave behind anything nasty (we use this for antique auto-restorations etc, it's passion/hobby). Just the normal drop or two into Hot Water and Bob's your Uncle. I am crazy, Rubbing Alcohol to clean everything, even tinned / plated, they still have machine oils & waxes on them,.

NO VINEGAR EVER !!! Vinegar is an ACID and will GREEN Copper & Brass ! Don't believe me, do it with a pure copper penny (pre-1960) and see what happens. IN a few days green will start to appear. Actually it's an aging trick to make copper look old and create an artificial verde green on it like it's been well weathered. Ever see Green Copper roofs ?

Posts only carry minimal juice, the power flows through the entire contact surface.

Serrated: VS Split Lock Washer for clarity (different folks, languages from world-wide)

 

[aaron_c]

Thanks @Steve_S !

Hmm.. If I don't use the vinegar+baking sodia mix, what should I use? Also, wouldn't mixing vinegar with baking soda (in a 1:3 ratio no less) leave us with something a bit basic? I honestly don't understand the idea of mixing vinegar and baking soda to clean metals--I did create a vinegar/baking soda volcano or two when I was young--but I believe I have seen it suggested in other situations, like for cleaning off black crap off the bottom of pans.

The second set of questions might not be something within your knowledge base. I don't mean to suggest you should scour the internet to find the answer or something (when I could do that if necessary). Just sort of...thinking out loud. And wondering if anyone knows the logic there.

 

[Steve_S]

Dawn Dish Soap is a great degreaser / cleaner & neutral.
Vinegar & baking Soda is a Volcano in a bottle, standard grade 5 science class experiment.
Right up there with "watch this nail dissolve in a glass of coca-cola" over 5 days.

 

[aaron_c]

Right up there with "watch this nail dissolve in a glass of coca-cola" over 5 days.

I have actually never done this one and kind of want to now.