Bus Bars, MRBF Fuses, and Copper Washers?

[wpns]

I've got bus bars:

https://www.amazon.com/dp/B0CSJXT7X3

MRBF fuses and holders:

https://www.amazon.com/gp/product/B0BR4VQJG5

And crimp-on wire terminals:

https://www.amazon.com/dp/B0CN4VL37G

And it looks like they almost fit, but won't make very good contact with the top of the fuse, especially the smaller sizes:


So I bought some copper washers:

McMaster-Carr

McMaster-Carr is the complete source for your plant with over 595,000 products. 98% of products ordered ship from stock and deliver same or next day.

www.mcmaster.com

Which are hopefully a 'not awful' solution, especially in the smaller sizes. Can/should I also use them on the larger sizes, of just where the hole in the MRBF fuse doesn't cover the lug?

Also, what's a good torque to tighten these down to? I'm not sure how hard the ceramic is and I don't want to crush the expensive (and hard to replace) fuses.

Thanks!

 

[timselectric]

Copper washer is a hard call. While it may increase the surface contact area on both sides. It also adds two contact surface points.
I can see good and bad, from their use. From the pictures it seems like fairly small conductors, so I would probably not worry about it.
As far as torque. If the fuse doesn't provide a spec, just make sure that it's tight enough to not be able to move.

 

[jcollman]

Watching this thread. The lugs in the bottom 4 photos look like they don't have much surface area.

 

[rhino]

Can you use larger cable size so that you can use one of the larger lugs?

 

[Q-Dog]

Where does the bus bar go? I would connect a bus bar to the fuse with an appropriate sized lug and cable, then connect all the small stuff to the bus bars.

 

[robbob2112]

You can use a pure copper washer, polish it, put some no-ox-id special A on it.

Better to get wide lugs

Amazon.com

They are wide enough to cover and not need the washer.

Torque specs is listed in the datasheet - if it is a real BUSS brand it is 6Nm...higher than I would have done than just by hand.

 

[OzSolar]

I've been known to "temporarily" use box lugs. Years later they are still working fine. YMMV

Yes, they are rated for fine stranded wire. Try to get the ones that tighten down with a hex allen, not a straight blade screw driver. Lots of surface area, accept a wide range of wire sizes.

Single Wire Electrical Lug Sizing Dimension Graphs and Charts, IHI Connectors brand

 

[wpns]

Can you use larger cable size so that you can use one of the larger lugs?

Yes, but then I'm 'wasting' 6GA wire for my 1.5A lights.

 

[wpns]

Where does the bus bar go? I would connect a bus bar to the fuse with an appropriate sized lug and cable, then connect all the small stuff to the bus bars.

Between the battery bank (100A fuse) and a 1500W inverter (75A fuse) and a 60W light (30A fuse) as loads.

And yeah, this is definitely going to be a "Perfect is the enemy of good enough" situation, unless I can get 5A 58V MRBF fuses the whole thing is going to be a bit of a compromise.

 

[wpns]

Got the first pass at the 3D printed cover working, it fits perfectly into the base of the busbar:

 

[wpns]

I decided that one monolithic cover was too much trouble, and didn't protect well enough, so I went with a separate bottom piece that goes under the MBRF fuse holders and uses the original bolts to hold it down:

Still thinking about the top cover, and how to design it for ease of printing...

 

[robbob2112]

I have to ask, why didn't you just order tripple MRBF holder?
the https://shop.pkys.com/Blue-Sea-5196-Terminal-Fuse-Block-for-3-Circuits_p_7754.html

 

[wpns]

I have to ask, why didn't you just order tripple MRBF holder?
the https://shop.pkys.com/Blue-Sea-5196-Terminal-Fuse-Block-for-3-Circuits_p_7754.html

I saw that, but can't remember why I didn't order it. I probably had some thoughts of wanting four fuses? I had already started down the path above, and was astounded with the pricing. Not that I didn't spend more than that with my final solution.

Thread 'Fuses for 48v Lynx Distributor'

Nov 3, 2024

I'm considering the Lynx Distributor for my 48V system. One challenge I see is availability of fuses.

Lynx Distributor uses Mega Fuses. While limiting myself to only reputable storefronts, I see a VERY limited number of options for 48V Megafuses.

Here's an example: https://shop.pkys.com/48-Volt-Mega-Fuses_c_956.html

The smallest available 48V Mega Fuse is 80 amps? How are we supposed to protect our smaller circuits?

Or, does anyone have a reputable source for 48V Megafuses smaller than 80 amps?

• chicagoandy
• Replies: 14
• Forum: Over Current Protection Devices

is how I ended up down this path. I should have been more patient with the various answers, but I had to order stuff to get all my ducks in a row for day after tomorrow, and it looks like I'm going to have to finish up in April instead.

 

[HRTKD]

Just an idea: Put the fuse on the existing busbar, use bigger cable so you can use a bigger lug that covers the entire surface area of the fuse. Run the bigger cable to a busbar with smaller terminals so your smaller wires with smaller ring terminals make better contact.

Or use a different type of fuse. Maybe an inline ATC fuse.

 

[740GLE]

Yes, but then I'm 'wasting' 6GA wire for my 1.5A lights.

On could say your wasting an MRBF fuse on a 1.5a load. . .

IMO I’d use a different fuse solution for 1.5a of load. That’s mighty low load.

What voltage is your system? Simple blueseas ATC fuse block is mighty handy for low current needs.

Blue Sea Systems 5045 Compact Blade Fuse Block with 4 Circuits

 

[robbob2112]

I guess it depends on if he already has the MRBF setup and it seems so or if he is still putting it together - in which case I would use a 1.5amp inline fuse.

 

[wpns]

On could say your wasting an MRBF fuse on a 1.5a load. . .

IMO I’d use a different fuse solution for 1.5a of load. That’s mighty low load.

What voltage is your system? Simple blueseas ATC fuse block is mighty handy for low current needs.

Blue Sea Systems 5045 Compact Blade Fuse Block with 4 Circuits

Yeah, in those other threads you can see I was looking for a 48V (58V) fuse, and they don't seem to come smaller/cheaper than 30A. Woulda Shoulda Coulda done the breakers thing.

 

[robbob2112]

you can get midget fuses and holders for lower amps - They don't go high, but they are handy for anything with a DIN rail. There are class T midget fuses for higher AIC - but with the low current it doesn't really matter

 

[HRTKD]

Height challenged fuses.

 

[Rexracer]

Maybe it's just me, but I wouldn't use a brass bus bar when there are so many copper options, and apparently conductivity of brass can vary a lot. I do like the suggestion of using a wider lug instead and copper washers. I know many of the better lugs are wider and thicker for the same size wire.

 

[Rexracer]

As for 1.5 amp dc loads, I would invest in a dc fusebox that takes standard auto type fuses. Then you can wire and fuse any 12vdc accessories you want. I even bought a USB block with multiple USB-A and C connections designed to plug into a 12v cigarette lighter plug. I clipped the plug, attached it to my fusebox, and have multiple USB plugs now for about $10.

I also made a panel with lighted pushbutton switches and 5.5mm x 2.1mm plugs (2@5 amps, 1@10 amps) for switched 12vdc accessories. Why not? I would use one of those for lights. I never could understand why people run an inverter just to plug in a transformer to charge a cell phone or tablet. Seems to me using the dc/cigarette lighter plug option makes more sense.