How many cables fit on a busbar?

[s/v Jedi]

For AIC, when the current arcs through the vaporized metal, it can then ionize the air and current keeps flowing forever. The more so with DC.

The picture I posted of my new cells with busbars... the busbars are 5 stacked layers of copper, instead of a single solid one. They are also bent in a loop in the center. The reason is to cope with expansion/contraction due to heat or to cells moving a bit. A solid busbar would start loading the terminals sideways, while this stacked and looped approach is flexible enough to absorb that movement. I mention this as it is an example of where something that seems not ideal (big solid copper better) is actually superior.

[s/v Jedi]

Oh I got distracted: for AIC, there are no rules of thumb. There used to be... before all the new battery improvements came. Take AGM: the reason that my Odysseys have a 5kA rating for short circuit current, while Optima, Lifeline etc. sit around 3kA is the TPPA technology of Odyssey. Thin plates of pure lead result in very high current capacity. This is also what makes them less than ideal fordeep cycle work.

So it’s best just to check the datasheet. I just checked my datasheet: max charge current 1.2kA... need some extra solar panels for that

[Bycrick]

I’ve actually seen a commercial version of bus bars similar in design. I just can’t remember where at the moment.

[Frankly]

If concerned about interrupt rating (a real concern with larger/ new technology banks), then you can insert a class T in series with the feed to the distribution system. Then use the lesser rated ANLs for the distribution legs.


It ain't just the wires, batteries have been known to explode under high fault current conditions.


Frankly

[chowdan]

Oh man am I jealous of those! It's going to be a fun build!!! I like the idea of external BMS far more than internals with drop in replacements. Don't like the idea of a BMS failing and a battery bank going down.

Originally Posted by s/v Jedi

Indeed. My starting batteries are Odyssey TPPL AGM and can do 5kA each. I will use 300A MRBF fuses on those. The new Lithium bank gets two 400A class-T fuses (24V and 12V center tap).

The picture is a teaser of the new cells I just received from China

[s/v Jedi]

So I have a question: my old 15 yrs) busbars are tin plated copper... from Blue Sea Systems, their Powerbar 600A rated. There are black spots all over them. I’ve been reading upon this and learned it is tin pest. What I can not find is if it screws with conductivity?

When I try to get rid of it, I really need to sand down to bare copper. I can easily tin that again by brushing some liquid tin on it after which that spot looks great.

The thing is that if it is not required, I’m not gonna bother with it. Sanding between the studs ain’t fun I think. The busbar does not detach from the plastic base so I don’t want to put a torch on it either...

You guys have any info/experience with this?

[Bycrick]

The tin coating does nothing to enhance conductivity. It might reduce surface corrosion of the copper which can reduce conductivity. I’d just clean it well, put it back together, and spray with a corrosion inhibitor like T-9 to keep it from happening again. As long as you clean the contact area of the bar, the rest is just aesthetics.

[stormalong]

Make your own buss bars. 1/4 X 1 inch silver flashed copper is $12 a foot at online metals. Make any length you want with as many studs as you want for far less than a commercially made product.

https://www.onlinemetals.com/en/buy/...ull-round-edge

[Wotname]

Originally Posted by s/v Jedi

So I have a question: my old 15 yrs) busbars are tin plated copper... from Blue Sea Systems, their Powerbar 600A rated. There are black spots all over them. I’ve been reading upon this and learned it is tin pest. What I can not find is if it screws with conductivity?

When I try to get rid of it, I really need to sand down to bare copper. I can easily tin that again by brushing some liquid tin on it after which that spot looks great.

The thing is that if it is not required, I’m not gonna bother with it. Sanding between the studs ain’t fun I think. The busbar does not detach from the plastic base so I don’t want to put a torch on it either...

You guys have any info/experience with this?

Try this article https://calce.umd.edu/tin-pests

The article above (and others suggest) tin pest (i.e. alpha-tin) is a semiconductor - clearly not good. Tin pest also crumbles away. This suggests to me that if tin pest was occurring, the alpha-tin has disappeared in the those spots and left the copper bar exposed to air. If so, the dark spots would more likely to be cuprous oxide (i.e. corroded copper). Again, not a good thing - most (all?) oxides are semiconductors.

Do you want to take a chance on an unknown surface conductivity of a busbar?

Question - is the busbar coating pure tin or a tin alloyed with other stuff?

[Wotname]

Also from the above link -
Xu strained the crystalline structure of the material by growing α‑tin samples in layers on InSb substrate. InSb has a slightly different lattice constant which puts strain on the α‑tin structure either by compression or tension. Furthermore, this discovery showed that α‑tin under a compressive strain is not an insulator, as had been thought. It turns out to be a Dirac semimetal. Based on Xu's calculations, α‑tin becomes a TI only under tensile strain conditions. His findings can open up many new research directions and help researchers understand and use α‑tin electronic properties.

and
The β → α transformation can be separated into two processes—nucleation and growth. The two processes occur at different rates, and nucleation is the critical event for tin pest formation. Nucleation is associated with long and uncertain incubation periods. Tin can spend anywhere from months to years in cold storage before developing observable signs of tin pest. Following nucleation, growth is relatively rapid, with 100% transformation to α‑tin observed to occur in as little as 30 days

Quite interesting.

[s/v Jedi]

Originally Posted by stormalong

Make your own buss bars. 1/4 X 1 inch silver flashed copper is $12 a foot at online metals. Make any length you want with as many studs as you want for far less than a commercially made product.

https://www.onlinemetals.com/en/buy/...ull-round-edge

You would toss a pair of $85 a piece busbars to go and buy materials to make your own? I think I'd rather sand and tin them

[s/v Jedi]

I think I will sand and tin them. The liquid tin works in seconds but the sanding is not my hobby

[sailorboy1]

Originally Posted by s/v Jedi

So here’s me considering to put 16 cables onto a 4-stud busbar.... thoughts?

I didn't read the replies.

I don't like it and bet you don't either or you wouldn't have asked.

[Frankly]

Brass or SS wire brush might be better and easier than sandpaper/ emery cloth.


Frankly

[stormalong]

Originally Posted by s/v Jedi

You would toss a pair of $85 a piece busbars to go and buy materials to make your own? I think I'd rather sand and tin them

There was a lot of discussion about buying Blue Sea Systems buss bars.

I put this out there to infirm people planning to buy something that does not meet their needs. They can make their own, exactly what they want for less money than buying something that is not as good for their needs.