DIY Bus Bars

[mitiempo]

Originally Posted by stormalong

The physical form of the fuse is irrelevant. The fuse or circuit breaker rating is what counts. It should be based on the amperage carrying capacity of the wire and expected load, up the next point where there is overload protection.

If you want to get as close as possible to the post it is relevant. An MRBF fuse is designed to go directly on the lug. Available from 30 to 300 amps.

https://www.bluesea.com/products/519...k_-_30_to_300A

AIC rating of 10000 @ 14 volts.

https://www.bluesea.com/products/518...al_Fuse_-_100A

[stormalong]

Originally Posted by mitiempo

If you want to get as close as possible to the post it is relevant. An MRBF fuse is designed to go directly on the lug. Available from 30 to 300 amps.

https://www.bluesea.com/products/519...k_-_30_to_300A

AIC rating of 10000 @ 14 volts.

https://www.bluesea.com/products/518...al_Fuse_-_100A

Interesting. Convenient way to install. The fuses are pricey. The exact same fuse made by the same manufacturer is less that half the price at
waytekwire.com. Still, if you can fit a high load circuit breaker there are no fuses to replace, just clear the problem and flip the lever to restore power.

PS. A little time searching found Littlefuse ZCASE fuses that can be mounted to a long stud directly. Either identical or almost identical to MRBF for an even lower cost.

[mitiempo]

Originally Posted by stormalong

A little time searching found Littlefuse ZCASE fuses that can be mounted to a long stud directly. Either identical or almost identical to MRBF for an even lower cost.

The ZCASE has a pretty low AIC rating - 2000 @ 32 volts vs the Blue Seas with 5000 @ 32 volts and 10000 @ 14 volts. ZCASE doesn't give a rating for 14 volts.

https://www.littelfuse.com/products/...ses/zcase.aspx

I use the MRBF fuses quite a bit, even for starting batteries with small diesels. They have a similar delay at rating as the ANL fuses so work well for high intermittent loads. They can also be added to busbars so you could have a bus with loads like windlass for example fuses right at the bus. Example below.

[CassidyNZ]

Originally Posted by mitiempo

There is nothing wrong with stainless bolts as the current doesn't pass through the bolt. The current is between the lug and the copper bar.

Same with Blue Seas bus bars - all their studs are stainless but not current carrying so it makes no difference.

Perhaps I’ve exacerbated my situation because I have on some bolts, more than one cable/lug and I’ve separated them with nuts. So I am depending on the bolt as a conduit for the current.

I probably need to revisit my setup and change a few things. The curious thing to me is that the reason that I have to change things is because of what I’ve read here, not because I’ve been having any problems.

[stormalong]

Originally Posted by CassidyNZ

Perhaps I’ve exacerbated my situation because I have on some bolts, more than one cable/lug and I’ve separated them with nuts. So I am depending on the bolt as a conduit for the current.

I probably need to revisit my setup and change a few things. The curious thing to me is that the reason that I have to change things is because of what I’ve read here, not because I’ve been having any problems.

While Stainless steel is a poor conductor compared to copper it is still a pretty good conductor. You are passing electricity through a bolt and nut, a short, wide mass of stainless. For practical purposes the losses are insignificant. To try to determine the losses you can measure the voltage drop across the bolt while you are passing a lot of current through it. It is unlikely that you will be able to measure any drop. Think of the bolt as a current shunt.

To make those losses smaller just remove the intermediate nuts and and bolt the terminals in direct contact with the copper buss bar. If you can't orient the terminals to be tightly secured without the nuts an alternative would be copper or brass spacers between them.

[Mike Burch]

Originally Posted by CassidyNZ

The curious thing to me is that the reason that I have to change things is because of what I’ve read here, not because I’ve been having any problems.

HAVE to? If it ain't broke, don't fix it!

[carstendenmark]

Cassidy, it does not get any worse to change into something better, right ?
Maybe you'll get a better performance, when all connections are right, who knows.

And, please read my former postings in this thread well ;-)

[RaymondR]

Originally Posted by carstendenmark

Hi, Raymond
Could you "quote" your first 5 lines, please ?

The special bolt type and extra work you suggest is not of any help, when the lug face is the main contact to the bar. Which is the case in almost every connection.

If you do cut the "difficult" thread (to avoid nuts) then just use an ordinary SS 316 bolt screwed in from the back side, secured with Loctite, and fix the lug on this, at the front side.

As you know, soft material threads requires a VERY soft hand when tightening a bolt. Once overtightened, the thread becomes a repair job.
The "hole" solution is safer.

Hey, mate - are we too far out (technically) for the common DIY'er now ? ;-)

My first experience of the consequences of the relatively high resistance of SS was when I used an SS bolt through a plywood bulkhead as a penetration rather than hole saw a hole big enough to pass the terminal and battery cable through. Some time later I smelt burning wood and discovered that the plywood around the SS bolt was singed. I have avoided SS as any sort of current conductor ever since and whilst brass is not as good a conductor as copper it is more readily available and more thread strip resistant.

There are occasions when the softness of copper is a nuisance, such as the terminals on anchor winch motors where the nut is likely to strip out if too much torque is applied. My practice is these instances is to make my own extended nuts from hex brass bar. I usually make them with at least 1/2" of thread which appears to solve the problem.

I'm sort of a belt and braces sort of bloke and lugs have two conductive faces so in high current circumstances I like the stud to assist as much as possible.

The countersunk brass bolt from the back side maximizes the area of stud at the conductive interface of stud and bar, is less resistive than stainless steel, allows one to hang the eyes of the lugs on the stud whilst putting on a washer and nut which is generally far easier than attempting to juggle a thread start whilst also offering the cable lugs to the screw, and allows the use of thicker nuts which consequently allow higher clamping forces. In addition, if one does through excessive enthusiasm, strip a thread one need only replace the stud to repair the problem rather than be challenged by a stripped thread in a bus bar.

For a number of practical reasons, the countersunk brass bolt from the back side is by far the better solution.

[skenn_ie]

Stainless is not great but OK for clamping. Just don't use it for current carrying. PURE aluminium is good for conductivity but not for threading. Tempered 6064 is good for threading but not conductivity.
https://www.thoughtco.com/table-of-electrical-resistivity-conductivity-608499

[stormalong]

Originally Posted by RaymondR

My first experience of the consequences of the relatively high resistance of SS was when I used an SS bolt through a plywood bulkhead as a penetration rather than hole saw a hole big enough to pass the terminal and battery cable through. Some time later I smelt burning wood and discovered that the plywood around the SS bolt was singed. I have avoided SS as any sort of current conductor ever since and whilst brass is not as good a conductor as copper it is more readily available and more thread strip resistant.

I would bet that the bolt was loose which caused the heat. Otherwise the bolt was to thin as a conductor. What size bolt and how much current.

As a mater of good electrical practice it would have been better to remove the lug and pass the wire through a hole. Every connection is a potential failure point, no mater how good it was when you made it. Especially on a boat. Vibration and moisture are mechanical connections' enemies.

[skenn_ie]

Originally Posted by stormalong

I would bet that the bolt was loose which caused the heat. Otherwise the bolt was to thin as a conductor. What size bolt and how much current.

As a mater of good electrical practice it would have been better to remove the lug and pass the wire through a hole. Every connection is a potential failure point, no mater how good it was when you made it. Especially on a boat. Vibration and moisture are mechanical connections' enemies.

Stainless is not a good conductor, nor is aluminium bronze to my surprise, but still a lot better than stainless

[RaymondR]

Originally Posted by stormalong

I would bet that the bolt was loose which caused the heat. Otherwise the bolt was to thin as a conductor. What size bolt and how much current.

As a mater of good electrical practice it would have been better to remove the lug and pass the wire through a hole. Every connection is a potential failure point, no mater how good it was when you made it. Especially on a boat. Vibration and moisture are mechanical connections' enemies.

The bolt was not loose after I installed it since it had a washer and nut either side of the plywood then another to hold the lugs on, it was loose in the plywood after the heat singed it.

The metalurgical specs for one of the resistance wires and 316 stainless are fairly close to each other.

I had another experience with SS on a used anchor winch motor I purchased which used to melt the solder on one of the terminals. After about the third removal and resolder close inspection revealed that the two nuts on the terminal were SS rather than chrome plated brass or copper. Switching the inner nut for brass and the outer for a DIY extended brass nut fixed the problem.

And another with SS washers both sides of the lug on battery terminals. I was amazed at how much resistance a very short length of SS in the current path can generate at engine cranking ampages.

[coopec43]

Originally Posted by coopec43

I agree 100% that I'll have to watch what material they are made of. My intuition tells me that as the motor is a diesel the load on the terminals will require robust terminals. Just looking at the photo they look like a bit of pressed stainless steel.


I saw your comment about the SS washer.


Yes one cable will have to go to the starter. Would you be happier with these?




Product: Unilug Two Up Positive & Negative Terminals
Listed here are the premium Heavy Duty Forged Battery Terminals from Unilugs, you will receive Positive and Negative with covers
Features:

• Heavy Duty Forged Brass Battery Lugs
• Anit-Rotating Terminal Clamp
• Moulded Nylon Battery Lug Cover
• Internally Threaded Adaptor Post
• Universal Flanged Hexagonal Bolts
• 1 x Positive & 1 x Negative

Building a yacht you need to keep an eye on what you are spending. The Unilug Two Up Positive & Negative Terminals cost $50 for the two.

I'm now looking at Military Battery Terminals that cost $19. (less than half). They are made of "lead alloy".

Am I "penny pinching" going for the Military Terminals?



Military Spec Top Post Battery Terminal End Positive and Negative with/ 2 Covers

Everything you need for a professional military style battery terminal conversion.
Great for multiple battery installations in race cars, off-road vehicles and RV's and anywhere battery performance is critical.

Features:
1, Made of lead alloy materials, which has good conductivity and corrosion resistance.
2, There is a clear positive and negative sign on the terminal; Each terminal can hold multiple battery cable.
3, It can be installed in the positive and negative poles of the battery; it can be used for battery extension, parallel connection, and ground connection.
4, Widely Used for Car Marine Boat RV Truck Camper ATV UTV Vehicles Battery Banks etc.

Kit Includes:
Positive and negative battery terminals




https://www.ebay.com.au/itm/Military...frcectupt=true

[coopec43]

There must be a couple types of Military battery terminals? Would it be necessary to go for die cast zinc alloy?

Military battery terminals are great for adding accessories like a winch or other high drain equipment (side terminals just won’t handle a winch). These Mil-Spec terminals also work great when used with dual (post and side) terminal batteries. You are able to use the side terminals for starting and powering normal circuits and the top posts for other added accessories. Also, they are indispensable for multiple or dual battery configurations. Or, if you just need to replace a battery cable, you can use these heavy duty terminals and a less expensive cable with eyelets or lugs on both ends. Real problem solvers!

For orders outside the US please contact us for shipping costs!

• Low profile design - only 3/4" tall
  
• Die cast zinc alloy
  
• 3.6 times more conductive than lead
  
• Corrosion resistant plating
• Lead free (RoHS Compliant)
  
• Mil-Spec A52425-1 & A52425-2
  
• Includes 1 positive and 1 negative terminal
  
• Large through bolt Is 3/8”, small clamping bolt Is 5/16"
• Also great for sound systems, lighting, hydraulics, marine applications or any high amp demand equipment

[coopec43]

There's more to the selection of terminal material than I thought. For example lead does not have the conductivity of copper but it does have an advantage over copper in that it can make a better connection because of its' softness.

Electrical conductivity of materials

https://www.bluesea.com/resources/10..._of_Materials/


Copper is more conductive, so why use lead battery terminals?

https://engineering.stackexchange.co...tery-terminals


Battery Terminal Connectors

https://www.wiringproducts.com/battery-terminals