Bus Bar Installations

[Scott T-Bird]

I'm sure I'm missing something, but I can't find a product that is ready-made for jumping the current from one bus bar to another. Reading a bit further, maybe I'm thinking about this the wrong way! For an unswitched positive bus, I bought 2 common bus bars from Blue Seas, rated for 150A, like this … https://www.bluesea.com/products/2307/Common_150A_BusBar_-_Four_1_4in-20_Studs_with_Cover

Each has 4 - 1/4" studs. I figured that I don't want to stack cables on the studs and I have two 2awg cables coming from house batt and ACR, one 4awg from the alternator switch, one 8awg from the charger and a multitude of 16awg's from various loads that want direct battery power, not through DC panel. Maybe some time I add a solar input. I have MRBF holders for the 4 & 8 gauge cables and the 16's have in-line fuses.
So my question is: What do you use to link the bus bars together if I am using all 8 studs? But, after reading the tech info on the buss bars, it seems that the studs can stack up to 4 terminals, and it may even be better to stack them on one bus bar, rather than using 2 bus bars. What do you think?

I have a 200A MEGA fuse that I planned to use, like this ... https://www.bluesea.com/products/category/15/49/Fuses/MEGA-AMG_Fuses
Is there any downside to using a fuse like this even though it is not necessary? It bridges the gap nicely and is compact. I was looking for a ready-made bar that would link the stud from one bus to the other, but I can't locate any product that seems to do this. I know I must be missing something. I'll want to do this on the negative side as well, where multiple negative cables come together.

If stacking is the better way to go, I simply do that …

 

[dlochner]

Scott, you have a couple of options.

I believe Blue Seas makes jumper bars to go between their busbars. A quick search of their site didn't show them, but perhaps a phone call to Blue Seas will be more productive.

Another alternative is to use a piece of 5/16" copper bar to connect the two busbars. (https://www.mcmaster.com/copper-bars) I used this to make a bus bar between a series of ANL fuses. Insulate the bar with heat shrink. Here's a photo of my positive bus bar.

 

[Ron20324]

Go to BlueSea.com , page 15 in the catalog, piece number 9159, it is a "M series Battery Switch Link Buss". 2 for 17.49 in the 2012 catalog I have. Rated 250 amps. When I was trying to wire in my Victrom 600, I could not find anything manufactured. I found 2 copper bars I think at Bacon's (McMaster has it) 1/4 x maybe 1.5 inches. Then later I saw this Blueseas link.

By the way, that upper right stud, it look like the yellow wire piece is sandwiched between the washers?

 

[Ward H]

@Scott T-Bird
As already mentioned, McMaster Carr for 1/16” or max 1/8” thick by 1” wide copper bar and make your own.
Those M series switch link bars have 3/8” holes in them.
The mega fuses have 5/16” holes in them. Are you putting the MRBF fuse holders on the bus bars? Those MRBF holders are made to go on 3/8” posts. Are you going to fuse off the bus bar or do you have the fuses on the batteries? Assuming they are at the batteries then it sounds like this bus bar is only being used to connect your alternator to the house bank and to supply the “always on” loads.
If so.........
You mentioned three larger cables so put one on each stud. Then put your 16 awg terminals one on each stud, until you have them all on the bb. I can’t imagine you have more than 8 always on loads so you end up with maybe one large lug with two smaller terminals on top of it per stud. One bus bar is all you need. Those in line fuses need to be within 7” of the bus bar or you have unprotected 16 awg wire.

If you wanted one bus bar for the larger lugs and one for the 16 awg wire I’d use an in line fuse with 12 or 14 awg wire tails to connect the two bus bars and with a fuse sized for the 16 awg wire.
Probably a 15 or 20 amp, depending on the loads the 16 awg wires carry.

 

[dlochner]

By the way, that upper right stud, it look like the yellow wire piece is sandwiched between the washers?

Interfernce with HS terminal insulation can usually be mitigated by using an M8 flat washer as opposed to a 5/16" flat washer. Also most M8 flat wahsers are thicker than a 5/16" washer but they have a slightly smaller OD.....

 

[Justin_NSA]

Scott, you have a couple of options.
Another alternative is to use a piece of 5/16" copper bar to connect the two busbars. (https://www.mcmaster.com/copper-bars) I used this to make a bus bar between a series of ANL fuses. Insulate the bar with heat shrink. Here's a photo of my positive bus bar.
View attachment 160692

I did something like that based on Main's article when I replaced my charger. I used similar buss bar and fuses to distribute the charger outputs to my two battery banks and system "A/B/All switch. Last weekend I used the last piece of bar material to create a common battery ground buss. I no longer have to stack or daisy chain cables on the batteries.

 

[dlochner]

I did something like that based on Main's article when I replaced my charger. I used similar buss bar and fuses to distribute the charger outputs to my two battery banks and system "A/B/All switch. Last weekend I used the last piece of bar material to create a common battery ground buss. I no longer have to stack or daisy chain cables on the batteries.

I found inspiration in the same place. Isn't that where most of the good ideas about boat wiring come from?

It is important to use copper and aluminum or stainless steel. SS does not conduct well and Aluminum can corrode and react with the copper in the wire and terminal ends.

 

[Ward H]

Isn't that where most of the good ideas about boat wiring come from?

Mine did. He does great work, of course, so why not copy him when possible.
I also look at the product photos on Blue Sea website. Some will show install examples. That's where I got the idea of labeling wires on the ring terminal body itself, instead of on the cable.

 

[Ron20324]

I think the OP needs also to consider how many batteries he will have. A local electrician pointed out the cross-section area (maybe circular mils or mm2) needs to be about the same as the buss bar or the other way around. I realized, since I would end up with three batteries, that I needed to upgrade my buss to accomodate triple the amperage, 3 x 100 fused, in my setup.. Formulas for calculations can be found online.

 

[Ron20324]

Scott, how many amps and/or size buss bar are you in need of? I don't know if I have any brass bar left, but I do know I would NOT have trashed any leftover. I'll look. A metal recycling center may have scraps.

 

[Justin_NSA]

My tinned copper buss bar was pretty thick. 3/8" maybe. It's amazing how hot the whole bar got while I was drilling the stud holes. Excellent conductivity!

 

[Scott T-Bird]

All, right now I have 2 grp 27 wet cell "deep cycle" batts (Walmart) for house bank and a small GEL start battery. I'm using DCP switch to isolate house and start. I have emergency isolation switches for house bank, start, and the alternator. My diagram is virtually identical to the diagram that Maine Sail posted for DCP with emergency isolation switches. He shows just a single + bus with 4 posts and he stacks cables at the post that have leads from the house EIS, ACR and DCP.

I had thought that it was undesirable to stack cables in this manner, so I intended to use 2 bus bars and link them. In some further reading, it seems that stacking the cables is not a problem, and possibly good for higher amperages. I'd like to know more about this.

In my reading, I'm beginning to have doubts about the bus bar. I have purchased the Blue Seas 100A common bus bars with 1/4" studs for both positive and negative buses. Perhaps they are not adequate. Coming into the bus is the 80A alternator (via isolation switch) with 100A fuse on 4awg and the 30A charger on 8awg with 40A fuse. @Ward H tells me it's not a good idea to use the MRBF holders with 3/8" hole coupled with the 1/4" stud. The studs have a serrated flange nut, so I was less worried about this issue. I also have misc. 16awg wires with in-line fuses that need the unswitched battery bus for bilge, stereo memory, battery monitor, and such. There are maybe 4 or 5 of those. My intention is to clean up the battery posts and use just 1 MRBF holder on each bank for 200A fuse to protect all the 2awg cables. 200A may be a bit light, but I've had no blown fuses since they were installed on my batteries. Also, I purchase all the 2awg cables ready-made with 3/8" lugs, so is this also an issue on the bus bar? They make a 250A bus with 5/16" studs and a 600A bus with 3/8" studs.

I have no high amp currents, or at least none that exceed the starting current. I anticipate that future battery purchases for this boat would be either 3 GRP 24's or 2 GRP 27's & 1 GRP 24 (for starting). I don't anticipate ever wanting any more than about 200 ah for house bank. So no more than 2 house batts and a starting batt. I also can't use tall batteries without significant modification so golf carts are out of the question. So it's either GRP 27's or GRP 24's, that's all I have room for.

 

[dlochner]

I had thought that is was undesirable to stack cables in this manner, so I intended to use 2 bus bars and link them. In some further reading, it seems that stacking the cables is not a problem, and possibly good for higher amperages. I'd like to know more about this.

There are a few parameters for stacking cables.

• Put the highest draw cable on the bottom, and then next highest draw and so forth with the smallest cable on top.
• No washers between the cables nor at the bottom.
• A SS washer on top is good.
• Make sure there are enough threads on the stud after tightening the nut.
• It is permissible to use a nylon lock nut, this eliminates the lock washer.
• 4 cables is the magic number, at least for batteries.

Blue Seas has been using shoulder nuts that have an serrated flange instead of lock washers.

 

[Ward H]

Those bus bars with 3/8” studs are pricey, around $60 on Amazon. You can get that 250amp #2027 W/ 5/16” studs for around $20. I wouldn’t hesitate putting the MRBF holder on that bar if needed. You can also get a version with 5/16” studs and a few #10 screws for the smaller wires.

 

[Scott T-Bird]

You can get that 250amp #2027 W/ 5/16” studs for around $20. I wouldn’t hesitate putting the MRBF holder on that bar if needed. You can also get a version with 5/16” studs and a few #10 screws for the smaller wires.

I think that may be the ticket. The 2128 has two 5/16" studs and six #10 screws. I can use one stud with a double MRBF holder for the alternator and charger. I can use the other stud to stack two 2awg cables, and that leaves the screws for the misc. 16awg leads. Perfect … that gives me more room to organize cables.

 

[Ron20324]

Scott, I just came back from BaconSails.com. They had two items of interest:

A Marinco brand buss with 4 x 5/16 studs. $35.oo. New in the pack, but there MAY be some used. I didn't want to get my hands dirty looking through all the boxes. I don't believe Marinco is still in this line of electrics.

There was a 4 x 3/8 buss for 22.oo, slightly used. On each end is 2 screws for the little wires. No brand name, but it was pretty robust with a 9/16 or 5/8 thick bar.