How many cables fit on a busbar?

[Frankly]

Originally Posted by Manateeman

looked at silicon bronze buss bars that I made years ago and sprayed with Boshield after assembly and they worked fine and looked clean under the lugs.
More confused than ever.
Mark and his manatees

Conductors lower on the totem pole can be plused up by increasing cross section area. SB excels in corrosion dept.

Also don't loose site of what you are trying to achieve. Not catching fire (obvious), minimizing voltage drop (relative to what), longeivity, easy of assy, ect are all nice to have but nobody likely to make the bus structure out of silver bars.

The big loads in my yacht are bow thruster 300 amps but on for maybe 10 seconds, microwave 100 amps but maybe on for 10 or 15 minutes, alternator 90 amps but maybe 3 or 4 hours. Contrary to Bill of Rights, all loads not created equal.

Once read a short piece by Blue Sea about feeding in the middle to split current to increase ampacity.

Just don't put a SS flat washer under anything conducting.


Frankly

[GordMay]

Originally Posted by Bycrick

... A number that I got from a decent source, but which I can’t support, says that each "interface" for 2/0 wire is about .0002 ohms or 0.2 milliohms...

In reality, that number will be highly variable, depending upon quality of termination method, materials, & age.
See:

“Electrical Wiring Resistance Test Results” ~ by Jerry Powlas
➥ https://goodoldboat.com/march-2002-e...-test-results/

“Ohm’s Law & Boats”
➥ https://www.cruisersforum.com/forums....html#post1256

[s/v Jedi]

When you tin a copper conductor it becomes more corrosion resistant so that is the primary purpose of tinning. Second is malleability: when you clamp down on it, like a lug onto a busbar, the tin will squeeze into irregularities,increasing contact surface area.

For it’s lesser conductivity, this is a matter of layer thickness. The thinner the layer, the less resistance. This is why I decided to just brush the liquid tin on, instead of dumping the whole thing into the solution. My little test shows great results so that’s what I will do. I need my Fein Multimaster for sanding between the studs so it requires another trip to the biat just to get the tool...

At the moment I’m distracted with my Victron gear test bench... I put two Multiplus units in parallel and that is pretty cool the way they engineered that. Also, a 150/45 Smart MPPT and emulating a solar panel with a bench power supply and then reduce voltage or current limit and see the algorithm adapt to get as much power out as possible. It makes the power supply constantly flip from CC to CV and back, right at maximum current and just below max voltage.
Even at 32V, 30A input, the heatsink doesn’t get warm... impressive!

Last night I got a 50A plug and some wiring because I have a 50A outlet here so we can do some nice testing

[Bycrick]

Lead isn’t very conductive. But you can’t make batteries out of copper. So the plates are lead. One wouldn’t want to put the lead/copper connection INSIDE the battery where the copper wouldn’t like the acid. So the battery terminals are lead, good conductor or not.

Tin isn’t the greatest conductor either, but if it’s thin enough it doesn’t have a measurable effect. But it doesn’t improve conductivity either. It’s used as a corrosion inhibitor for the copper. If it’s gone, just clean up the surface, assemble the parts, and spray on a corrosion inhibitor. NBD.

But overall, I think the lesson here is that no matter how well you THINK you put a high-current circuit together, it’s never as good as you’d like it to be. You’re working where resistances of 1/10000 ohm are both measurable and potential problems. Any short-cuts or improper installation can have a lot more bad effects than you think.

If one believes the number from the SmartGauge people of 0.0002 ohms per interface using 2/0 wire and terminals, you’ll end up with 30-40 interfaces in the simplest "battery->fuse->switch->bus bar—>alternator->bus bar->measuring shunt->battery" circuit. That’s somewhere between 0.005 - 0.010 ohms. Not counting the resistance of the wire or the various components. At 100 amps, that’s 0.5 volts drop minimum. Maybe 5%. And if you take shortcuts, that will get worse quickly.

A 2/0 lug with a 5/16” hole has about 5-8% MORE contact area than the same lug with a 3/8” hole. So using that old lug with a 1/2” hole because it’s the only one you’ve got is truly a big deal.

Trying to measure fractions of a milliohm isn’t easy because you have to account for all the resistance in the measurement connections. Trying to measure and display a few millivolts change requires a meter than can measure and resolve and micro volts. You’re not going to do that with a meter from Home Depot.

In my battery circuit of about 20’ total (ie, both ways), I have more losses in the connections than anyplace else. If I went from 2/0 to 4/0 wire the only improvement would be the reduction of resistance in the connections.

[Frankly]

"I couldn’t sleep at all last night” maybe Chuck Berry

Not up to the Thunder Bay Study but quick and dirty.

If interested refer to the pictures to make sense out of this (no electrical diagram or detail report will be forthcoming)

3/16 X 1” junk yard copper bus bar tinned with silver bearing no lead solder (all battery feeds on lower end)

BB stack up- BB with 5/16” SB stud, 100A ANL fuse blade, CU flat washer, SB split lock washer, SB nut

Load End stack up- 5/16” SB Stud, CU flat washer, fuse blade, #1AWG lug, CU flat washer, SB split lock washer, SB nut

Load current 88 amps 12 VDC feeding sinewave inverter/ microwave

Drop along approx. 3” section of BB away from connections (hopefully uniform current density)
0.80 mV

Drop across BB connection to fuse blade 1.01 mV

Drop across lug neck to fuse blade 2.71 mV (makes sense, less contact surface)

Drop across 100A ANL fuse (blade to blade) 56.58 mV

Drop across total assy (including 3+” BB section) 62.7 mV

Conclusions: Do away with the fuses to minimize the voltage drop

[Bycrick]

My humble apologies. I, in no way, intended my bored musings to deprive you of your well-deserved sleep.

Your numbers sound about right. The bus bar works out to be about 10% more area than 4/0 wire. I thought the fuse number was interesting because we all forget that fuses HAVE TO get hot to work. So they have to have enough resistance to do so.

It also tends to NOT to support the resistance of each interface number of .0002 ohms,, because you’re fuse connection resistance was about 15% of that. That’s good news because that number always seemed a little high to me, based on total circuit voltage drop that I’ve carefully measured.

Good work.

[Manateeman]

Yesterday I had an interesting conversation with Blue Sea Systems technical support...always great people. I was curious why the BEP heavy duty 500 amp buss bars that I just purchased, were much thinner and had much less mass than the Blue Sea buss bars. How could they rate the same. The big heavy thick Blue Sea buss bar is rated differently than the BEP bars. The Blue Sea bar is rated end to end...not, middle to end. The BEP bars are fine and designed at the same vertical distance as their other components. The two are sister companies.
I’m sticking with Blue Sea System and I’m not going to produce my own bronze bars or connectors anymore. I asked about tin. The tech guy explained it beautifully...it a real thin layer but the resistance to corrosion is good so using tin is a small price to pay...it’s not gold or silver...but it works. The BEP system looks neat and clean but I never had any issue with Blue Sea Systems so I’m sticking with them.,
There is also a lot of good information available from Victron Energy...they have a free online book “Wiring Unlimited”. and a lot of more on their home page.
Perhaps someone could make this a click link...I don’t know how. Maybe someone could make a list of free books on wiring for the forum members.
Happy trails to you
Mark and the Saturday Night Pizza Party manatees

[Bycrick]

Interesting. So, tins cheap and works to keep it looking nice. Gold is more expensive and not a good high-current conductor. Silver would be lovely, but not worth the increased cost. Again points out that just because something is "rated" at X doesn’t mean much unless you know what the rating is based on.

BEP has, or had, a line of products that might/might not have been better than the Blue Sea stuff individually. But it had the great advantage that all the pieces were based on a common size factor, so they were really easy to mount compactly on a backing board, and were the same height. Thus one could lay out the board, attach all the components and use standard length connecting strips.

Ya gotta look at all the angles.

[stormalong]

Originally Posted by Bycrick

Interesting. So, tins cheap and works to keep it looking nice. Gold is more expensive and not a good high-current conductor. Silver would be lovely, but not worth the increased cost. Again points out that just because something is "rated" at X doesn’t mean much unless you know what the rating is based on.

onlinemetals.com sells silver washed copper bar for less than tin plated. Silver, gold or tin plating is so thin that the cost of the material is less than the cost of applying it. Silver washed is thinner than tinned but it doesn't take much to protect the copper.

IMO you are better off with a DIY custom made buss bar that fits your needs than an off the shelf compromise. I have, IIRC four buss bars aboard, all made to fit my needs. One of them is a foot long ground buss behind my circuit breaker panel, drilled and tapped for the ground wires for everything that goes to the panel. Yes, it took a while to drill and tap 48 holes but the results make for a very neat installation. The heavy duty high current buss bars are much simpler to make and take no time at all. Less time than ordering and waiting for a less suitable commercially made ones.

[s/v Jedi]

Originally Posted by stormalong

onlinemetals.com sells silver washed copper bar for less than tin plated. Silver, gold or tin plating is so thin that the cost of the material is less than the cost of applying it. Silver washed is thinner than tinned but it doesn't take much to protect the copper.

IMO you are better off with a DIY custom made buss bar that fits your needs than an off the shelf compromise. I have, IIRC four buss bars aboard, all made to fit my needs. One of them is a foot long ground buss behind my circuit breaker panel, drilled and tapped for the ground wires for everything that goes to the panel. Yes, it took a while to drill and tap 48 holes but the results make for a very neat installation. The heavy duty high current buss bars are much simpler to make and take no time at all. Less time than ordering and waiting for a less suitable commercially made ones.

But you didn’t tin or silver it? If you did, how about the threads?

If I would make my own, I would use plain copper, hard-solder the studs in, then either use liquid tin or electroplate silver on. It would take me a lot of time, while now I click the mouse and people bring them to me while I do other jobs.

I agree that making it yourself is better and I very often make my own. But not when the difference in results is non existent because Ican onlyuse my time once and it would simply take too long.

[GordMay]

"Wiring Unlimited" ~ Victron Energy
A book about electrical wiring of systems containing batteries, inverters, charger and inverter/chargers
About ➥ https://www.victronenergy.com/blog/2...ing-unlimited/
PDF ➥ https://www.victronenergy.com/upload...limited-EN.pdf

[Bycrick]

Gord— Thanks for the article on butt splices. It was positively great.

If I absolutely have to make bus bars, I can and have done so using Jedi’s approach. But the idea that it’s cheaper or easier isn’t true.

[stormalong]

Originally Posted by s/v Jedi

But you didn’t tin or silver it? If you did, how about the threads?

If I would make my own, I would use plain copper, hard-solder the studs in, then either use liquid tin or electroplate silver on. It would take me a lot of time, while now I click the mouse and people bring them to me while I do other jobs.

I agree that making it yourself is better and I very often make my own. But not when the difference in results is non existent because Ican onlyuse my time once and it would simply take too long.

I did buy silver washed. The threads are left bare copper. The screws keep out the air. On bare copper I have sprayed Boeshield T9.

[Manateeman]

My dear Mr. Crick. You attributed three silly statements to me which I did not make and then ended with the recommendation to look at things from all angles.
Please let me set the record straight
When the the subject of tin pox came up on this thread I was surprised. I had never given a second thought to what I had considered minor tarnish.
When Captain May posted the list of metals, I was very surprised to find silicon bronze so far down the list because I had incorrectly assumed the high copper content made it a good conductor.
Then the thread drifted a bit into a more scientific discussion on resistance and measurements which I really didn’t find time to fully explore.
If you read my posts carefully, you will find I understood the advantages of the BEP system. As I am no longer building vessels for sale, speed of installing or a more modern look, are things which no longer are of importance.
I don’t understand why you felt it necessary to correct me with silly misquotes .
There is nothing about your experience as a boatbuilder, your vessel or your voyages. Certainly you have the right to privacy. I rather enjoy the various views and learn a great deal from members who have specialized expertise. I do not enjoy posts wherein statements are attributed to me which I never made especially when the intent of the post is to be cute or funny. I have no idea why you have taken issue with my post. I think both companies make excellent products. If you feel my post contains errors of substance, please post further.
If you simply enjoy cheap pot shots and snide remarks, have at it. Till then...
Happy trails to you
Captain Mark and his content manatees

[Manateeman]

I apologized to Rick privately. I owe him this public apology.
Rick, I’m very sorry for the post.
No excuses.
My bad behavior period.
Mark