Copper washers and brass bolts or screws for battery terminals

fafrd

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I see it as an advantage, if you break something it's likely to be the stud instead of the cell terminal ;)




It is a real problem. Now, is it a problem here? hard to tell. Also, it depends on a lot of factors, main one being humidity. On a boat it'll definitely be a problem, and in a house in the desert it'll definitely not. For cases inbetween it's complicated.

Personally I'd say if it's in a house in a non-tropical area then it's fine. If it's in a tropical area, or in the basement, or in a vehicule I'd say it would be wise to take precautions against it. But that's only an educated guess, YMMV.
So what would you advise for use in a basement at steady 65F year-round but humid during the rainy season (Bay Area)?

Between stainless, brass, zinc-plated or aluminum and posts (grub screws?) or bolts, I’m a bit lost as to the most reasonable thing to do.

Also, as far as the zinc-based paste to use to protect the aluminum terminals from oxidation, I’ve understood that that is a good idea regardless of environment & fastener solution but a specific product recommendation would be appreciated (never used the stuff before).
 

BiduleOhm

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Interesting point.

I am kinda thinking of a cracked aluminum stud while the system is under load - the resulting loose connection would become an inadvertent TIG welder with nothing to stop it. (have your cameras ready for the viral YouTube video!)

I will vote for the most mechanically sound fastener possible in this application.

Of course you're supposed to stay under the maximum recommended torque. Also, the same will happen with any more robust stud, you'll just strip the terminal threads instead of the stud. But I don't see how it can happen after your put the battery together, if it happens it'll be when you thighten the nuts.


So what would you advise for use in a basement at steady 65F year-round but humid during the rainy season (Bay Area)?

Humid = galvanic corrosion can happen.


Between stainless, brass, zinc-plated or aluminum and posts (grub screws?) or bolts, I’m a bit lost as to the most reasonable thing to do.

I would do as I said: aluminium for everything so no galvanic corrosion to worry on the cells terminals. Then for the two last busbars to the battery cables (who will most likely have copper lugs) I'd use either aluminium or copper bolts/nuts/washers (so only two dissimilar metals, no need to introduce a third one...) and dielectric grease. That's what I plan do on mine actually (basement, 15-20 °C).

Again, just my recommendations, feel free to implement only part or none of it if you don't like it ;)
 

fafrd

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Humid = galvanic corrosion can happen.
Does that mean if I keep the battery in a case warmed to ~25C throughout the wet season (winter) and only ventilate with 65F cellar air (or dry outside air) if/when temps rise up to high during the summer, I’ll have less/little to worry about as far as galvanic corrosion?

I’m already concerned my cells may not be charging properly at temps below 65F (because they were so cheap or whatever) so I’m considering keeping them within the recommended temperature range of 23-27C.

If another benefit of keeping the cells warm and dry is galvanic corrosion becomes a non-issue, that might be the straw that breaks this camel’s back (meaning I’ll take the plunge).
I would do as I said: aluminium for everything so no galvanic corrosion to worry on the cells terminals. Then for the two last busbars to the battery cables (who will most likely have copper lugs) I'd use either aluminium or copper bolts/nuts/washers (so only two dissimilar metals, no need to introduce a third one...) and dielectric grease. That's what I plan do on mine actually (basement, 15-20 °C).
‘Everything’ including busbars (meaning go to aluminum busbars)?

From earlier inputs, I thought plated copper busbars addressed 90%+ of the galvanic corrosion concerns between aluminum terminals and copper busbars.

Aluminum busbars seem like a real PITA, especially since I’m considering switching to braided plated copper busbars to address concerns of mechanical stress during charge/discharge cycles (within a clamping fixture).

So I was planning on using plated copper for all connections to aluminum terminals (including connections to BMS and ANL fuse) and was trying to decide between bolt & nut options (stainless, brass, plated steel, aluminum; bolts or studs).

At either cellar temps of 65F & moist during winter or controlled temps of 25C and dry year-round, I’d appreciate your advice on which metal to use for studs and nuts securing plated busbars to aluminum terminals.

Thanks.

Again, just my recommendations, feel free to implement only part or none of it if you don't like it ;)
As I said, your recommendations start pushing me into the zone where I start thinking it may to be easier to keep my cells nice and cozy (warm and dry) rather that going to all that trouble to design them to be better able to withstand a harsher environment...

But I greatly appreciate your suggestions.
 

BiduleOhm

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Does that mean if I keep the battery in a case warmed to ~25C throughout the wet season (winter) and only ventilate with 65F cellar air (or dry outside air) if/when temps rise up to high during the summer, I’ll have less/little to worry about as far as galvanic corrosion?

Probably, but then it would be best to not ventilate, just have a small few holes so things can equalize.


I’m already concerned my cells may not be charging properly at temps below 65F (because they were so cheap or whatever) so I’m considering keeping them within the recommended temperature range of 23-27C.

18 °C is totally fine, it's actually better than 25 from what I saw.


‘Everything’ including busbars (meaning go to aluminum busbars)?

Yes.


From earlier inputs, I thought plated copper busbars addressed 90%+ of the galvanic corrosion concerns between aluminum terminals and copper busbars.

Yes, plated copper will be fine ;)


Aluminum busbars seem like a real PITA, especially since I’m considering switching to braided plated copper busbars to address concerns of mechanical stress during charge/discharge cycles (within a clamping fixture).

So I was planning on using plated copper for all connections to aluminum terminals (including connections to BMS and ANL fuse) and was trying to decide between bolt & nut options (stainless, brass, plated steel, aluminum; bolts or studs).

As said, feel free to mix and match the advices. I was just describing what I think is best, but of course "best" depends on your specific needs and what you want...


At either cellar temps of 65F & moist during winter or controlled temps of 25C and dry year-round, I’d appreciate your advice on which metal to use for studs and nuts securing plated busbars to aluminum terminals.

Basically the less dissimilar metals you have the better. For example if you start having zinc plated steel nuts, stainless studs, brass washers, copper busbars and aluminium terminals you'll have more problems no matter the environment...


As I said, your recommendations start pushing me into the zone where I start thinking it may to be easier to keep my cells nice and cozy (warm and dry) rather that going to all that trouble to design them to be better able to withstand a harsher environment...

But I greatly appreciate your suggestions.

No problem, I can see you use your brain cells so you'll probably chose a good solution and don't have problems, don't worry too much ;)
 

Bob B

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It seems to me that there is somewhat of a juggling act to determine what is most important for a given installation.

I have been mulling over the various considerations and have NEARLY arrived at the conclusion that for my mobile environment, the durability of stainless studs and copper bus bars out weighs the galvanic corrosion risk. The risk of galvanic corrosion can be easily mitigated by the use of a noalox compount.
I am partially swayed by my bad experiences with aluminum wire in my house .... I can visualize .... correctly or not .... that constant vibration could cause displacement in the aluminum and cause poor connections over time.
 

Hedges

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My first concern regarding loosening of connections would be the stiff battery cables applying torque to the screws holding them.
I would look for either a geometry that didn't apply torque or a limber connection as mechanical strain relief.

Similar to what I see with "SMA" style RF connectors. If right-angle they loosen easily, but not if in-line.
 

fafrd

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Probably, but then it would be best to not ventilate, just have a small few holes so things can equalize.
If I decide to go that route, the idea would be to use a heating pad to maintain at least 23C (or whatever) and use a fan, possibly connected to a vent/hose going outside, to blow in cool 65F air whenever temps climb past 27C (or whatever). There will only ever be ‘ventilation’ when the entire compartment starts approaching a danger zone (likely only because of sustained current draw).
18 °C is totally fine, it's actually better than 25 from what I saw.
I have one cell that appears to have taken significantly less charge to 3.65V at 18C but I only discovered that at the end of the capacity test.

Charged at 25C the cell actually delivered a hair over 280Ah, so now I need to circle back and repeat a test charging a 18C to understand whether the potential issue is ‘real.’

These grey market cells came so cheap, there is almost certainly something wrong with them.

EVE’s specification only shows 100% discharge performance at -25C and >= 70% discharge performance at -20C; nothing about charge performance at temps other than 25C+/-2C.

So charge performance at temps lower than 25C is completely unspecified.

On top of that, if a cell fails the >=70% discharge at -20C, this could easily be the reason EVE sells these cheap cells off through grey market resellers.

So I’m happy with how my cells perform at 23-27C but will remain cautious about assuming that performance translates blindly down to -8C without verifying first.
Yes.


Yes, plated copper will be fine ;)


As said, feel free to mix and match the advices. I was just describing what I think is best, but of course "best" depends on your specific needs and what you want...

Basically the less dissimilar metals you have the better. For example if you start having zinc plated steel nuts, stainless studs, brass washers, copper busbars and aluminium terminals you'll have more problems no matter the environment...
So one last question then:

If I’ve got plated copper busbars on aluminum studs, would plated steel studs, nuts and washers count as adding another dissimilar metal or does the ‘plating against plating’ mean plated steel will behave about as well as plated copper (which I am not interested in).

Taking your words at face value, with aluminum terminals and plated copper busbars, II should either go with aluminum hardware or plated copper hardware (from which I prefer the idea of aluminum).

Plated steel would be easiest and cheapest if that will work about as well...

No problem, I can see you use your brain cells so you'll probably chose a good solution and don't have problems, So don’t worry too much ;)

Yeah, right. Between clamping fixtures, avoiding corrosion, assuring grey-market cells are well-matched and properly top-balanced, selecting the correct BMS for your application, and then all the complexity of wiring and charging systems and voltages, if you are not comfortable ‘worrying’, this is probably not the right hobby for you 😉
 

Just John

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My take on the problem: use aluminium studs, nuts and washers, and aluminium busbars. That way you only have the 2 connections to the loads to worry about galvanic corrosion and it's not on the expensive cells but on some cheap and easily replaceable busbars ;)
The aluminum studs, nuts, and washers are not really good choices. Their purpose in this instance is to provide a firm physical connection between the battery terminal and the busbar. We already have problems with stripping the threads on the terminal, now we would just have additional problems with the threads on the studs and nuts, and easily deformed washers. Aluminum busbars would of course solve the problem of galvanic corrosion, however they would need to be substantially larger, and would just move the problem to wherever you decide to change from aluminum as a conductor to copper in the circuit. The stainless steel (or brass) in this isn't supposed to be carrying current anyway, as long as the connection lasts as long as the battery, we don't really care. I've also thought of using aluminum, but resistance is an enemy, and copper is a better conductor. Just my personal choice, but switching to copper as soon as possible when carrying current is my choice. Just my thoughts.
You are 100% correct, everything in engineering is a compromise.
 
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fafrd

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The aluminum studs, nuts, and washers are not really good choices. Their purpose in this instance is to provide a firm physical connection between the battery terminal and the busbar. We already have problems with stripping the threads on the terminal, now we would just have additional problems with the threads on the studs and nuts, and easily deformed washers. Aluminum busbars would of course solve the problem of galvanic corrosion, however they would need to be substantially larger, and would just move the problem to wherever you decide to change from aluminum as a conductor to copper in the circuit. The stainless steel (or brass) in this isn't supposed to be carrying current anyway, as long as the connection lasts as long as the battery, we don't really care. I've also thought of using aluminum, but resistance is an enemy, and copper is a better conductor. Just my personal choice, but switching to copper as soon as possible when carrying current is my choice. Just my thoughts.
So what hardware would you use to provide a ‘firm physical connection’ between an aluminum terminal and a plated copper busbar? Stainless, bronze or plated steel?
 

Just John

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Aluminum studs seem extremely weak for this sort of thing.
Is galvanic corrosion a real problem that needs to be solved or a rare corner case in specific applications?
At least in house wiring (the exact thing the anticorrosion compounds were designed for), it tends to become a problem somewhere between 5 and 10 years after the connection is made. That "estimate" is from personal experience with aluminum house wiring in two different houses. I will note that both houses were in Florida, where corrosion is much more of a problem than the desert where I currently live. :)
 

Just John

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It is a real problem. Now, is it a problem here? hard to tell. Also, it depends on a lot of factors, main one being humidity. On a boat it'll definitely be a problem, and in a house in the desert it'll definitely not. For cases inbetween it's complicated.

My take on it is:
The smallest tube of Ox-Gard cost me $3.48 (and free shipping). All you need to do is wipe the face of the terminal and busbar. That tube will be plenty for my 16 cells, and at least 100 more (probably more like 2 or 3 hundred more).

Pretty cheap, and no longer a worry.

I'll be honest, I live in the desert, it isn't a big worry for me anyway. I have however lived in two different houses in Florida (30 years apart) that had aluminum wiring, and it was indeed a big problem there. Then again, when capacity testing cells, I'm using a fuse.
 

Bob B

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Oh .... I forgot about the heating and cooling in a mobile environment .... that can loosen any connection ... and I suspect a lot worse with aluminum.

At least in house wiring (the exact thing the anticorrosion compounds were designed for), it tends to become a problem somewhere between 5 and 10 years after the connection is made. That "estimate" is from personal experience with aluminum house wiring in two different houses. I will note that both houses were in Florida, where corrosion is much more of a problem than the desert where I currently live. :)
In my house, not only did they use aluminum wire, but they did the "poke Home" terminal connections on the switches and outlets instead of putting them under a screw connection. Yep major nightmares about 10 years in.
 

Steve_S

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My Powerhouse is warmed only to 10°C/50°F and we see -30°C/-22°F here, not unusual at this time of year.
40°C/104°F Also happens far too often in summer and with 80%+ humidity, major UGHNESS ! and great for creating sorrosion.
Copper Busbars, Stainless Steel Screws. No Corrosion issues.
Copper Busbars, Brass Grub Screws & Nuts, No corrosion issues.
Aluminium Busbars & Stainless screws, No corrosion.

All Battery Packs within closed boxes.
Humidity can reach 80% within the powerhouse depending on weather & conditions.
I see ZERO difference between the two packs with Noalox Applied and the two packs without.
- I am Land Locked and no sea spray within 1500 kms.
 

BiduleOhm

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If I decide to go that route, the idea would be to use a heating pad to maintain at least 23C (or whatever) and use a fan, possibly connected to a vent/hose going outside, to blow in cool 65F air whenever temps climb past 27C (or whatever). There will only ever be ‘ventilation’ when the entire compartment starts approaching a danger zone (likely only because of sustained current draw).

Oh ok, I see ;)


I have one cell that appears to have taken significantly less charge to 3.65V at 18C but I only discovered that at the end of the capacity test.

Charged at 25C the cell actually delivered a hair over 280Ah, so now I need to circle back and repeat a test charging a 18C to understand whether the potential issue is ‘real.’

These grey market cells came so cheap, there is almost certainly something wrong with them.

Probably a bit of both. Li batteries capacity is dependent on temperature, you won't damage it at all at 18 °C but you'll have a bit less usable capacity than at 25 °C.


If I’ve got plated copper busbars on aluminum studs, would plated steel studs, nuts and washers count as adding another dissimilar metal or does the ‘plating against plating’ mean plated steel will behave about as well as plated copper (which I am not interested in).

Taking your words at face value, with aluminum terminals and plated copper busbars, II should either go with aluminum hardware or plated copper hardware (from which I prefer the idea of aluminum).

Plated steel would be easiest and cheapest if that will work about as well...

Depends on the plating. Copper is usually tin plated while steel is usually zinc plated so not ideal (but not the end of the world either).
 
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Steve_S

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ROH OHHHH
Mixing up of Celsius & Fahrenheit can be HAZARDOUS !
Ask ANY Airline Pilot that got fuelled up in Litres instead of Gallons and only realized it at 30,000 feet while panicking to locate a close landing field.
 

BiduleOhm

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The aluminum studs, nuts, and washers are not really good choices. Their purpose in this instance is to provide a firm physical connection between the battery terminal and the busbar. We already have problems with stripping the threads on the terminal, now we would just have additional problems with the threads on the studs and nuts, and easily deformed washers.

You'll strip threads long before you can deform any washers... Also you don't add any problems, max allowed torque will be the same as before so as long as you stay below it it'll be totally fine.


Aluminum busbars would of course solve the problem of galvanic corrosion, however they would need to be substantially larger, and would just move the problem to wherever you decide to change from aluminum as a conductor to copper in the circuit.

That's kind of the point. Instead of having the problem on terminals you move it were it'll not damage them, and instead of having at each terminal you only have the two main connections to worry about.


I've also thought of using aluminum, but resistance is an enemy, and copper is a better conductor. Just my personal choice, but switching to copper as soon as possible when carrying current is my choice. Just my thoughts.

Well, usually yes, but by using larger busbars you can have the same resistance as copper, and aluminium is a lot cheaper than copper so price for added material isn't a concern.
 

sid the seagull

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Brass is perfectly FINE for this use... Brash Washers are also available.
Mixing all sorts of metals....

Great recommendations on Battery terminals, thank you .

On the connecting interface , My jbd 150a Bms has fairly solid copper busbars attached already so brass connections will be best, I appreciate the advice.
 

tabs_xyz

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It seems to me that there is somewhat of a juggling act to determine what is most important for a given installation.

I have been mulling over the various considerations and have NEARLY arrived at the conclusion that for my mobile environment, the durability of stainless studs and copper bus bars out weighs the galvanic corrosion risk. The risk of galvanic corrosion can be easily mitigated by the use of a noalox compount.
I am partially swayed by my bad experiences with aluminum wire in my house .... I can visualize .... correctly or not .... that constant vibration could cause displacement in the aluminum and cause poor connections over time.
The way I understand it, aluminum doesn't have the pliability that copper has. So expansion and contraction from temperature changes will cause aluminum wire to loosen on outlet screw terminals over time. And you must go to the next larger size or two to handle the same current copper can handle.
 
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