@fhorst From an Engineering standpoint, I disagree with you on many points. The addition of more metals will only complicate the corrosion model. Among other factors, differences in thermal expansion rates are ignored in your theory. As the aluminum contracts, the silver won't follow once it is solidified, and the stainless has its own coefficient. This will leave gaps and break your seal. It is also one of the top reasons that fasteners come loose.I looked up the M38999, no way you can connect this with our aluminium terminals.
For galvanic corrosion, no I did not read your personal posts, apparently you didn't read mine either
You will find we are largely on the same page.
Corrosion, being galvanic corrosion or "normal" both can be prevented with a seal.
Like our cars work perfectly with some paint.
Yes, after a decade or so, it does get issues at the edges.
Probably for a yet plane the paint needs to be applied more often for the pressure reason you mentioned.
Corosion needs oxigen.
Prevent by sealing it with lubricant or paint both have the same results.
Paint just lasts longer.
Problem with most paint is that it's non or bad conductive layer.
Silver conductive paste/paint solves that issue.
Compared to lubricant like vaseline, it's a whole lot better.
I'm not taking my Powerwall apart twice a year to apply new lubricant!!
Reply some one the sides isn't working, the center rod / screw / bolt is having the same loss of lubricant.
Tin and copper have large difference for voltage, so does tin and aluminium.
Yet tinning aluminium and copper is quite standard, and doesn't give problems on its own.
Solder on copper PCB lasts several decades without showing signs of galvanic corrosion.
Zinc coated copper should desolve the Zinc, right?
Huge difference...
Yet, most coated lugs one can buy are Zinc or Tin coated.
Simple deduction makes that coating is preventing corrosion aka oxidation.
By lack of oxigen.
Sure, miniscule air pockets will be there, and they will expand some, or atleast have higher pressure.
(Air can be compressed really easy)
A coating, silver based or other, compressed with tinned copper bus-bar on top...
Those trapped micro air pockets will have a hard time expanding strong enough to break the seal.
This is not a problem
Problem might be is the oxigen in this micro pocket.
Oxigen is oxidation aka corosion.
Galvanic corrosion can not occur without oxigen.
I think it's good to say that it is not possible to totally prevent Galvanic corrosion.
We can reduce its effects!
A lot.
Best would be to use the same metal for all connection and connection materials.
There where this is not possible to make use of coated parts.
I used electroplating to Tin my Bus-bars.
Looking back, Zinc would have been a better choice.
This doesn't make the work useless, it does reduce / slow down the Galvanic corrosion process.
Not sure if it's doable at home, but electroplating with aluminium could even be a better solution.
Or hot dipping.
(Most Iron rods are hot dipped with zinc)
It is what it is, my Bus-bars are Tin plated.
Next step, for all is the same, connect the bus-bar on the aluminium terminals.
oxi-guard or vaseline/petroleum jelly are non conductive and kind of seal of the aluminium and copper.
For me, I'll be using silver paint, the type one can use to repair PCB lines.
I'll clean the aluminium surface, sand paper it light with high grid (1500) with a flat surface (small hand mirror)
this will make as flat possible surface.
The Tinned copper bus-bar will get the same treatment.
(First the Tin, then the aluminium as aluminium oxidize the fastest)
As I make pairs, and the pairs into series, it's easy to have 2 x one bus-bar connect the 2 cells.
making them this way I have the bus-bars mounted quickly on the terminals.
later, when all pairs are finished, I need to unscrew the nut, place the 2 connection Bus-bars for the series and tighten the nuts for permanent.
time will tell if the silver based conductive layer is eating the aluminium terminals.
My experience with silver conductive paste and aluminium heatsinks is positive, no galvanic corrosion after 5 years.
aluminium surface still as smooth as before.
I don't think it will as there is no oxigen.
Perhaps in 10 years or longer the edges might get some galvanic corrosion.
I bought the 50 kWh LiFePO4 to be able to use at least 7 years, (economic) expect 10 and hope 12-15 years.
in normal days the cells are used for 25%.
the days with less sun, slowly more.
42 X 340 watt panels don't make a lot of energy during overcast and rain.
Living off grid makes it nesececery to have spare energy for 7 overcast/rainy days.
that is in reality about 10 week a year.
For the other 42 weeks the cells are just lightly discharged at night.
At night we use without crypto mining about 1kw per hour, depending on the weather the mining is stopped.
Normally it like 750-1000 watt, depending on coin / calculation method.
That is my personal setup, slightly off topic with the crypto, for many readers the way the cells are mounted, is on topic.
I discussed galvanic corrosion on this forum before, and other forums.
It's real. It does happen. You can not stop it, at all.
Corrosion is a fact.
Question is, how bad is it, how bad is it for you?
Are you living close to the coast?
(Salty air)
Do you have higher temperature difference?
Do you have your cells outside or inside your home / RV / shed?
Do you have controlled environment (air conditioning)
All important questions to answer to decide how bad the galvanic corrosion will hurt you, or (almost) not at all.
For me, close to Laos border in Thailand, far away from the sea
Cells are indoor, air conditioned room , 26-28 degrees at battery array.
(Cells are on the floor, in a section of our bedroom, "energy closet" silenced for inverter noise, and well ventilated)
That is as optimal is I can get them.
For all people, depending on how long you want to use your cells, optimization of location / temperature & moisture can make years difference.
2 different metal touching eachother will give galvanic corrosion.
Sealing one metal with an other won't, as there no oxigen.
This sealing can be electroplating, hot dipping, "explosion fusion" (I don't know official name, with great force like explosion 2 metals can be joined), probably a few other methods I did not mention.
Painting is one of the sealing methods.
Most base paint for Iron contain (or used to contain) lead (oxide)....
I am thinking about buying some magnesium wire and wrap it around the terminal, and go to the top, the rod, after all is connected.
Contact with all 3 different metals
(Aluminium, copper, stainless steel 304, or for me add Tin and silver)
If any would be an easy way to control galvanic corrosion then this is probably the most visable and controllable / replaceable method available.
Look twice a year and if one one location the magnesium wire is eaten away, you simply apply new.
It's really hard to find wire for me, ribbon, loads, and cheap.
View attachment 25313
1Rolls 99.95% 25g New Magnesium Ribbon High Purity Lab Chemicals | eBay
100% brand new and high quality<br>100% brand new and high quality<br>Material: Magnesium<br>Quantity:1 pc<br>Color: Silver<br>Fineness: 99.95%<br>Weight: 25g<br>Width: 4mm (5/32")<br>Thick :0.2mm<br>Note :Due to the difference between different monitors, the picture may not reflect the actual...www.ebay.com
About 3 dollar for a meter
Scissors will make it easy to cut in half or less, making your own wire out of ribbon
This 3 dollar worth of magnesium should last you longer than the LiFePO4 cells...
That is, as long as you don't light it.
As a kid my chemical kit had some magnesium...
I still smile thinking about lighting those strips..
That was great fun.
40 years later probably less impressive.
I can tell for sure that the 3 dollar won't hurt your budget badly, won't damage the cells if used with sense (don't make a short) and will be the first to show galvanic corrosion.
Not only show, but moves the problem all together to a location that is easy to manage (= replace)
I cannot advice to make washers out of magnesium and place them between the copper bus-bars and aluminium terminal.
It will be eaten, and once gone, your setup will have no longer good contact.
Probably crappy way of saying this in English...
Not native English sometimes is difficult to explain things.
God speed and good luck with your installation!
You can worry all you need (I did my share) and find solutions that will work for you.
With this, only time can tell what was best.
It's a trade-off between optimal contact and galvanic corrosion prevention/reduction.
I personally would have paid the 5 dollar extra to have copper Terminals, if it was available.
I did see one copper, one aluminium terminal in a brand LiFePO4...
Your system will probably work just fine. Not because you add silver, tin, or magnesium to your terminals, but because you keep them climate controlled.
I find that most people in the US that are looking into lithium batteries are looking for solutions to RV, boat, or home power systems and do not necessarily have the luxury of climate control for the batteries. This is evidenced by the emphasis on a low temperature cutoff in the BMS. This is the audience to whom I address my solutions.
As you mentioned, It is quite simple to keep everything aluminum from the cells all the way to the terminals where your power is used. A light coat of connector lubricant is sufficient to seal aluminum against corrosion. No sense in complicating the matter.
If the aluminum threads on the cells will hold 8Nm, then the threads on the aluminum fasteners will also.
