1/8th copper or 4mm stainless steel for busbar?

Googling electrical standards is not hard.

Given the corrosion and termal expansion trouble history of aluminum electrical conductors in a home environment, using aluminum conductors or bus bars on a boat is poor judgment. You can do it and it will work for a time, but that doesn't make it good practice.

You can't get copper bus bar material at an electrical store and most good hardware stores. I don't get it. Just get the right stuff.

Another common mistake is to slip stainless washers into the stack. A big no-no. They will get hot, which can lead to loosening of the stack over time.

I'm a little shocked at the number of people that have no idea how poor a conductor stainless really is.
 
Galvanised steel is another possiblity. A length of builder's metal flat bar for instance.
It has the advantage it can be drilled (if not ready drilled) and tapped, making an easy low-profile solution.
Aluminium can be ok, but a proper job probably involved silver plating the contact areas... Seriously, I've seen a great many things grounded to tapped holes in lumps of aluminium with no issues. Use plated steel screws or studs not stainless though.
 
pvb said:
Total bollocks! You didn't read Nigel Calder's little mistake about that, did you?
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Explain. "Total bollocks" requires documentation. ABYC does not expect ANY washers to be used within the ring stack, with only a stainless washer on the top. The stud is not considered to be the conductor, because the rings are not clamped to it. The rings themselves must be copper.

The OP also has six rings and a nut (makes 7) on a stud, which exceeds the ABYC limit, which is 4.

E.9.16.K10. No more than four conductors shall be secured to anyone terminal stud. If additional connections are necessary, two or more terminal studs shall be connected together by means of jumpers or copper straps.

You may not care about ABYC. Your choice.
 
thinwater said:
Explain. "Total bollocks" requires documentation.
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Some years ago, Nigel Calder’s wrote an article on electrical safety in Yachting Monthly, in which he warned us that our boats are in danger of spontaneously combusting due to our lousy wiring. Why? Because he warned us that using stainless steel washers in bolted connections “puts a relatively high resistance in the circuit”. How high? According to Calder, it’s so incredibly high that it “seriously impairs the performance of the equipment” and, worse still, “creates a lot of heat - more than enough in many high-current circuits to start a fire”.

I don’t know what sort of “high-current” circuit Nigel had in mind, but if we assume that few cruising yachts are likely to see more than around 300A flowing through a circuit (equal to the current taken by a fair-sized bowthruster or inverter), a typical half-inch stainless steel washer will introduce a resistance which causes a voltage drop of about 2 millivolts (0.002V) which, with 300A flowing, will cause a heating effect of 600 milliwatts, about the same as a Christmas tree light! And highly unlikely to start a fire (although Calder claimed to have “seen several fires that originated this way” - really?)

That's why I said that your claim was total bollocks.
 
In other worlds, it's kind of accepted that stainless is a crap conductor, its surface properties can cause problems.
If you want to use stainless to actually carry current, you should think about the surfaces, not just the bulk resistance.
A stainless bolt holding conductors together is a different proposition.
'stainless' of course covers a multitude of sins.
In avionics, we used to specify stainless with some sort of coating/plating, most of which got banned for being toxic and/or carcinogenic. You can do worse than specify gold plating.
 
pvb said:
Some years ago, Nigel Calder’s wrote an article on electrical safety in Yachting Monthly, in which he warned us that our boats are in danger of spontaneously combusting due to our lousy wiring. Why? Because he warned us that using stainless steel washers in bolted connections “puts a relatively high resistance in the circuit”. How high? According to Calder, it’s so incredibly high that it “seriously impairs the performance of the equipment” and, worse still, “creates a lot of heat - more than enough in many high-current circuits to start a fire”.

I don’t know what sort of “high-current” circuit Nigel had in mind, but if we assume that few cruising yachts are likely to see more than around 300A flowing through a circuit (equal to the current taken by a fair-sized bowthruster or inverter), a typical half-inch stainless steel washer will introduce a resistance which causes a voltage drop of about 2 millivolts (0.002V) which, with 300A flowing, will cause a heating effect of 600 milliwatts, about the same as a Christmas tree light! And highly unlikely to start a fire (although Calder claimed to have “seen several fires that originated this way” - really?)

That's why I said that your claim was total bollocks.
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Your opinion, then.

I have seen batteries with heat damage where a stainless washer was inserted under the stack. The cranking amps of a good size diesel can be in the range you suggest. It is also possible that disimilar metals corrosion was a factor; your calulation assumes perfect contact. Fires, I can't say. But ABYC does have stack limits based on experience. And why would you insert a stainless washer, anyway? Pointless.

The only place I would expect to see a real problem is on a starting current lug.
 
I have limited experience with this "marine" home made electrical bus-bar theory but I am an electrician and there is no question it needs to be copper bus-bar, brass bolts and washers, some contact grease on the connections.
The csa needs to be bigger than the largest cable so not flattened copper pipes etc. if you really want to make something find yourself a lightning protection company and ask for an off cut.

Aluminium is a nightmare, you would need copper to aluminium lugs crimped on the cable (very expensive and not stocked by anyone we use) they fuse the Al to the Cu so it cannot corrode and you are not clamping dissimilar metals together. Don't use brass bolts anywhere near aluminium they don't like each other.

The lugs need to be clamped directly to the bus-bar, that is what should carry the current not a washer - if you want to fit any washers they need to be between the nut and the lug and of the same material as the bolt.
 
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thinwater said:
The OP also has six rings and a nut (makes 7) on a stud, which exceeds the ABYC limit, which is 4.

E.9.16.K10. No more than four conductors shall be secured to anyone terminal stud. If additional connections are necessary, two or more terminal studs shall be connected together by means of jumpers or copper straps.

You may not care about ABYC. Your choice.
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May I suggest that you raise the matter with the boat builder. Contact details :-

Beneteau
Legal and Compliance
Z.I. des Mares
BP 66
85270 Saint Hilaire-de-Riez
France

thinwater said:
I'm a little shocked at the number of people that have no idea how poor a conductor stainless really is.
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Thanks for sharing your wisdom. Here's my contribution to patronising comments. "a little knowledge can be very dangerous" ;)
 
thinwater said:
A big no-no. They will get hot, which can lead to loosening of the stack over time.
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pvb said:
Why? Because he warned us that using stainless steel washers in bolted connections “puts a relatively high resistance in the circuit”.
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Am I missing something in that both of you seem to be saying the same thing about using stainless steel washers in busbar connections

High resistance and causing heat.

In my view any form of washer in an electrical connection face is not necessary and as said above can cause issues

In my case washers are only used under the head of bolts or nuts never between clamped surfaces and all wire connections of crimped or soldered lugs wirh set screws into tapped holes in the bus bar (lug to bus bar direct contact.
 
Rogershaw said:
Am I missing something in that both of you seem to be saying the same thing about using stainless steel washers in busbar connections

High resistance and causing heat.
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Read post 26 again; I was disputing Calder's claim. A heating effect of 0.6W is negligible and won't start a fire!
 
pvb said:
Read post 26 again; I was disputing Calder's claim. A heating effect of 0.6W is negligible and won't start a fire!
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Ok I may have missed that.

So are you saying that a washer or stainless steel is OK between connections and the bus bar and will not potentially cause a problem.

Any heating effect could cause a fire depending on the temperature then heating effect caused. It also depends on the heat transfer rate in that particular setup.

The current rating of a cable is dependent on how and if the cable is enclosed and what the ambient temperature of the environment is. Again this is all has an effect on how hig the temperature will get. It all about the heat in from the resistance and the heat out heat transfer away from the joint.

To put it another way the 0.6W heating effect is only one part of the equation.
 
Many helpful and informative posts, thank you.

I appreciate the value of the forum where most offer non-judgemental help, advice or simply their thoughts and opinions based upon their training, qualifications and experience.
 
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