stainless as conductor on battery posts

[Tator]

I've noticed that on my new Lion LiPo4 (yet to be installed) batteries that the posts appeared to be made of stainless steel. I called and confirmed this with the company. Due to being more resitive, I have always been careful not to use stainless hardware on electrical connections, I am wondering how concerned I should be about this. I've viewed Youtubes of the batteries being subjected to large amp charges and discharges without seemingly there being a heat problem. I was planning on using a cap screw to connect the lugs to the posts and am wondering on what material they should be made from. Any thoughts?

Tator

 

[Bacchus]

I have not even looked a Li batteries so can only ask...
Is there a lead contact at the base of the SS threaded post similar to typical FLA or AGM battys?

If yes that will be the primary path for conducting.
Flat area of post and terminal larger area for contact.
The nut basically provides the clamping force to maintain contact. IMO that is the logic of NOT placing any washers under or between terminals but OK at top of a multi trrminal stack. Also best practice to stack larger cable / terminal sizes at bottom and decreasing to smallest at top of a stack.
All FLA & AGM threaded posts & nuts I've seen are SS.

 

[DDW]

SS isn't very conductive compared to copper, but then lead isn't either. When you have everything installed if might be a good idea to put the heaviest continuous load on the circuit and measure the voltage drop across the terminal, or the heat rise in it.

 

[Tator]

Both the base and the post appear to be stainless.

 

[High Wire]

The important bit is not to have any SS BETWEEN the battery post and the terminal, such as a lockwasher. Also make sure the hole size matches the stud size.


Read Steve's article
https://stevedmarineconsulting.com/battery-terminals/

 

[Iggy]

I am not really up on Li batteries. But from what I have read, you can not use them for starting, yes? If yes, than the load on that connection should not be that high.

 

[DavidM]

I just got a couple of G31 AGM batteries from WindyNation and their terminal screws were 3/8" stainless steel. They screw into a female SS battery post that has an O/D of 5/8" which is about the same size as 4/0 cable. Who knows what the size of the internal buss is.

Yes, copper is about 40 times more conductive than stainless steel. But the distance is short, maybe an inch making the voltage drop the same as about 3' of 4/0 cable.

So I wouldn't worry about it. The voltage drop in any cable plus the voltage drop inside the battery will be much more.

David

 

[Xlantic]

Lead is a lousy conductor but it is 4x more conductive than stainless steel.

Plain steel is a bit better than SS.

Copper is more than 10x as conductive as lead and aluminum is not far.

https://www.tibtech.com/conductivite.php?lang=en_US

 

[AusCan]

Stainless steel is less conductive than copper or lead in a laboratory, but in the real world it is often better.
There is little voltage drop in the small distance. Also, there is less chance of corrosion at connections which is the biggest source of voltage drop in a marine environment.

 

[DavidM]

Stainless steel is less conductive than copper or lead in a laboratory, but in the real world it is often better.
There is little voltage drop in the small distance. Also, there is less chance of corrosion at connections which is the biggest source of voltage drop in a marine environment.

David

 

[Comodave]

Yes, less likelyhood for corrosion on the terminals which is good. Besides the battery designer took the S/S into account.

 

[Tator]

Comodave-What material are your connecting cap screws made from?

 

[Comodave]

I don’t actually know what the terminal posts are made out of on the batteries but I am using a copper bus bar to connect them and S/S bolts to attach it.

 

[caltexflanc]

The reason lead is used for terminals in traditional batteries, AGM and FLA, is because all the internal metals are lead. It makes sense to me that lithium batteries might be a whole 'nother story.

 

[FF]

When assembling load centers or batts the use of a star washer to help tension the connection seems inexpensive insurance.

Even small loads will create heat that can push the connection looser every use , the star washer pushes it back tight.

 

[GoneDiving]

The female threads on lithium battery posts can be very easy to strip especially if multiple or thick lugs reduce the number of threads on the bolt actually engaged.

For the lugs that I use more often (eg the most -ve and +ve) using studs and nuts rather than bolts is much more reliable. I just cut the heads off some M6x25 bolts and screw them in full depth and tighten.

 

[Tator]

What does -ve and +ve mean?

Tator

 

[GoneDiving]

What does -ve and +ve mean?

Tator

Negative and Positive.

I'm my case I never touch the middle connections so just use the normal post bolts. I do however add, remove or adjust the first negative and last positive ones (and these also have the thickest/more lugs) so this is where I prefer to use studs and not the short bolts.

Cheers

 

[EngNate]

Not only is SS a fairly poor conductor, it develops a film which has very poor conductivity. This film is what makes stainless stainless. I am going to throw out a guess that the terminals are actually nickel-plated, common for electrical hardware.

 

[GoneDiving]

Not only is SS a fairly poor conductor, it develops a film which has very poor conductivity. This film is what makes stainless stainless. I am going to throw out a guess that the terminals are actually nickel-plated, common for electrical hardware.

My raw cells appear to be an aluminium alloy. That's why they are so soft. Unlikely a generic 6061 but maybe a busbar alloy that resists forming a protective oxide coating.

 

[Tator]

As I said, I called the manufacturer and was told they were stainless.

Tator

 

[Comodave]

Lion Energy confirmed to me that the posts are S/S.

 

[ProMaritime]

Yes, and I use SS washers and nuts on them. It's worked for almost 40 years.

 

[Iggy]

I called Blue Seas Systems the other day on a question. They told me that on there larger VSR and Remote battery switches that there post are made of copper and there tinned plated. Here is the funny part!! The nuts that they come with are S.S.

 

[Steve DAntonio]

I just got a couple of G31 AGM batteries from WindyNation and their terminal screws were 3/8" stainless steel. They screw into a female SS battery post that has an O/D of 5/8" which is about the same size as 4/0 cable. Who knows what the size of the internal buss is.

Yes, copper is about 40 times more conductive than stainless steel. But the distance is short, maybe an inch making the voltage drop the same as about 3' of 4/0 cable.

So I wouldn't worry about it. The voltage drop in any cable plus the voltage drop inside the battery will be much more.

David

A stainless washer is very thin but inserting it between a ring terminal and battery or bus bar, on a high current circuit, will definitely heat up the washer, I have witnessed this on inverters and thrusters and have the photos to prove it.

The real issue is the mass of the stainless. A hair like strand of copper wire is far more conductive than the same size strand of stainless wire, but if the stainless wire is the thickness of a pencil (just arbitrary examples I have not calculated the ampacity of each) then its resistance, or conductivity, may be equal to the copper. We use iron engine blocks to conduct starting current, and because of their mass the resistance is comparatively low.

The blades on the SmartPlug are stainless steel, but they are large...

In general, however, it's best to avoid using stainless as a conductor as a field expedient. If the conductivity has been calculated by an equipment manufacturer and deemed acceptable, that's another story.

What's the brand of Li Ion battery? Is it possible these are in fact tinned copper?

 

[Tator]

It is a Lion brand battery. Company has stated that they are indeed stainless.
Tator

 

[Nick F]

Quote: EngNate: Not only is SS a fairly poor conductor, it develops a film which has very poor conductivity. This film is what makes stainless stainless. I am going to throw out a guess that the terminals are actually nickel-plated, common for electrical hardware.

+1 I have had exactly this experience when I worked in fuel cell research. The coating that develops on pure stainless can be very non-conductive.

Nick