Copper washers and brass bolts or screws for battery terminals

sid the seagull

Slip slop slap
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Nov 12, 2020
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I’m in the midst of potting together two 12v banks of eve cells acquired from Amy.

I’m planning on using a combination of M6 brass bolts and copper washers to connect busbars and terminals.

i figured they were higher conductivity so should help the current flow.

am I missing anything, is there reasons why such an approach should be avoided .
 

sid the seagull

Slip slop slap
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Nov 12, 2020
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I just watched wills latest video, brilliant . It got me thinking that perhaps I would be better served by creating brass studs. So I’ll be doing down that path.

mom not able to find brass split washers so I’ll need to use stainless there . However I’m planning brass studs , copper washers and brass bolts with a stainless split washer, unless I can find a brass split washer.
 

Factory400

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I have put brass studs, washers, and nuts on my test bank as an experiment.

Trying to figure out how to out the 250lb bank on my engineering bench to see if I can measure any improvements with my very sensitive Keithley DMM. My hypothesis is that there will be little to no benefit. Perhaps even a negative benefit since I expect the brass to stretch before I get to the torque required to make full terminal contact. So, my guess is that even though the brass is a better conductor, I would be sacrificing the main terminal pressure.
 

sid the seagull

Slip slop slap
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My main concern was the melting temperature of brass, but as my system has been over specified I’m hoping that will never be an issue .

Factory, I’m keen to hear your findings with your sensitive equipment.

I appreciate the comments blokes
 

Steve_S

Offgrid Cabineer, N.E. Ontario, Canada
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I have Brass Greuib Screws & Nuts on some batteries, Stainless Bolts on others.
Brass is perfectly FINE for this use... Brash Washers are also available.
Mixing all sorts of metals.... Think about grade 7 science class... DERP !
Stick with Stainless or Brass.
Melting Point of screws ? ARE YOU BARKING MAD ? that's over the deep end, seriously. Shake Head and engage critical thinking...
 

Just John

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The purpose of the stud, nuts, and washers are to hold the terminal and the battery terminal in as tight a connection as possible. It's not to carry current. Most people choose stainless steel for its strength and corrosion qualities. Brass as well. I think Brass is just more traditional on boats (strange things happen with saltwater and two different metals). Copper is a poor choice for this purpose, BTW, too soft.
 

Factory400

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you'll be limited by the torque that the cell terminal can handle which is only about 4Nm.
The data sheet on my CALB cells (from memory) was about 20Nm or so. I would think that 12-14Nm is reaching the point of diminishing returns.
4Nm seems remarkably low......is this for the aluminum cased cells?
 

Factory400

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I have Brass Greuib Screws & Nuts on some batteries, Stainless Bolts on others.
Brass is perfectly FINE for this use... Brash Washers are also available.
Mixing all sorts of metals.... Think about grade 7 science class... DERP !
Stick with Stainless or Brass.
Melting Point of screws ? ARE YOU BARKING MAD ? that's over the deep end, seriously. Shake Head and engage critical thinking...
The melting point of brass is about 900C-1000C
Yeah.....that would be pretty mad indeed! If the battery terminals ever saw a fraction of that - I would be running as fast as possible. :eek:
 

BarkingSpider

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Even better, get gold plated bolts!

Seriously though, stick with the original factory fittings and spend the extra time and money on additional batteries, or working out where you are wasting power with a WattMeter and get more efficient devices.

Reducing the length of your cables is in fact a better savior of power.

The metallurgy problems from mixing all those metals will be a nightmare.
 
Last edited:

Bob B

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The data sheet on my CALB cells (from memory) was about 20Nm or so. I would think that 12-14Nm is reaching the point of diminishing returns.
4Nm seems remarkably low......is this for the aluminum cased cells?

There was another thread about torque where people were seeing threads being stripped with only 6 nm. Don't remember what thread that was.....These were EVE cells.
 

cinergi

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The data sheet on my CALB cells (from memory) was about 20Nm or so. I would think that 12-14Nm is reaching the point of diminishing returns.
4Nm seems remarkably low......is this for the aluminum cased cells?

yes. A bolt or stud into the terminal of the aluminum can’t withstand more than 4.5 or so.
 

HaldorEE

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Apr 20, 2020
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I have Brass Greuib Screws & Nuts on some batteries, Stainless Bolts on others.
Brass is perfectly FINE for this use... Brash Washers are also available.
Mixing all sorts of metals.... Think about grade 7 science class... DERP !
Stick with Stainless or Brass.
Melting Point of screws ? ARE YOU BARKING MAD ? that's over the deep end, seriously. Shake Head and engage critical thinking...
Got a link to the brass grub screws? I can't find anything longer than 12mm in brass. I am looking for M6 x 20mm. 12mm isn't long enough for double bus links.
 

Factory400

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Got a link to the brass grub screws? I can't find anything longer than 12mm in brass. I am looking for M6 x 20mm. 12mm isn't long enough for double bus links.

25mm and 30mm available.
 

Factory400

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25mm and 30mm available.
Their inventory is insane - I got Titanium bolts from them delivered same day (only in LA area)
 

HaldorEE

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Weird thing is I shopped there and couldn't find them. I had to use the exact search terms. I ordered M6x1mm by 20mm brass set screws and M6 brass nuts. Stainless steel into Aluminum is not great. It can cause galling.
 

Aaron_85

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Townsville, Australia
The purpose of the stud, nuts, and washers are to hold the terminal and the battery terminal in as tight a connection as possible. It's not to carry current. Most people choose stainless steel for its strength and corrosion qualities. Brass as well. I think Brass is just more traditional on boats (strange things happen with saltwater and two different metals). Copper is a poor choice for this purpose, BTW, too soft.
John knows.
The terminal-buss bar connection should be carrying most of the current, not the fastener that holds it together.
Galvanic compatibility is more important, which brass and aluminum (battery terminal) are not. The brass will cause the aluminum to corrode
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