Searching for: Mega fuse holder that bolts directly to battery terminal

[pekka8]

You wouldn't need to use that expensive ($60+) surface mount fuse block, you can also get one of the ones that mounts directly (and compactly) diretly to the battery post. I like this style that allows 2 of the marine fuses, each protecting different circuti. I'll use one for my "big" inverter and one for my much smaller inverter. Approx $16.

Do you know if this works with Eaton and Blue Sea fuses? So you can stack two of them in battery terminal?

 

[Vigilant24]

Do you know if this works with Eaton and Blue Sea fuses? So you can stack two of them in battery terminal?

I >think< the fuse holders for these MRBF fuses are common to all brands, but I am not sure.
The dual fuse holder just has an extended tab from the battery that allows two fuses to be put flat on it (rather than just one). Rach fuse can protect a separate circuit, and they aren't stacked or in series (so blowing one won't affect the other fuse).

There is a picture at this link. I've seen these dual-fuse holders sell for about $16 elsewhere.
https://www.amazon.com/Dual-Termina...se&qid=1684761777&sprefix=mrbf,aps,712&sr=8-8

 

[Vigilant24]

MRBF fuse holder would be nice, but then have to stock different types. Or use more expensive MRBF everywhere. Could also be harder to find in case you run out.

Yes, getting a multitude of formats/types is a problem, especially if it is for a remote/emergency installation where it might be hard to get replacement bits and flexibility is important.

The Megafuses (of brands I know and trust--Littlefuse, Buss, etc) sell for about $10-$15 each in small quantities. They are cheaper if bought by the bag with an unknown branding from China. The MRBF fuses from brands I know (Buss, etc) cost about $15 each. If no-name brands are okay, this place offers the MRBF fuses for about $5 each. A dual-fuse block complete with two fuses sells for about $20.
https://www.amazon.com/VOZINMOST-Hi...2728&sprefix=mrbf+fuses+eaton,aps,126&sr=8-39

I don't plan on burning through a lot of these (hopefully!), so replacement cost isn't a huge factor for my case.

 

[Warpspeed]

Why not just use a couple of stand off insulators ?
These are available fairly inexpensively in sizes from small to enormous, very easy to use, will not melt or burn, and very strong.

 

[Vigilant24]

Why not just use a couple of stand off insulators ?
These are available fairly inexpensively in sizes from small to enormous, very easy to use, will not melt or burn, and very strong.

Those .might< work, and they would be cheaper than a purpose-built MRBF fuse holder. Points I'd want to consider:
1) Technical: Would they adequately do the same thing? It would be useful to make sure that the contact area with the fuse is sufficient, if their contact metal is compatible with the fuse material, etc.
2) Legal/liability: If the fuse fails to function and the sharp-eyed inspector sent by the insurance company comes sniffing around for a reason to deny paying a fire claim, I'd like to have complied with the guidance of the fuse manufacturer. (I think this is a very unlikely situation for me, but it may mean a lot to others).
3) Practical: That final positive terminal on the battery pack is some valuable real estate. If the post is physically monopolized by a stand-off insulator with an MRBF on it, then everything else will be in serial with that fuse. That might included lesser loads (e.g. another smaller inverter, DC loads, etc) and also the input from the solar charge controller. I suppose we could stack up additional fuses pagoda-style to protect these smaller loads, but it would get cumbersome and if a fuselower down in the stack gets blown, everything loses connection >and< the whole stack neds to be disassembled to change a lower fuse. Using the standard fuse holders puts just one tab on the battery post (and that tab can host 1 or 2 MRBFs each with its own load) and there's still vacant threaded space remaining on the battery post for future expansion.

Anyway, the standoff insulators might work just fine, I don't know.

 

[Warpspeed]

The main issue here is not physically supporting the fuse, but anchoring the ends of the often massively thick and heavy cables going to the fuse.
To change the fuse, you just remove a couple of nuts, swap out the fuse then back into operation.
The cartridge fuse itself is designed to contain all the fire and explosive fury within, no need for any additional enclosure to protect nearby parts.

These standoff insulators are parts DESIGNED for high voltage heavy duty electrical applications. That is what they are for. They meet all the statutory requirements for electrical insulation and flammability, so in that respect are at least equal to a purpose built fuse holder.

The theory of using electrical lugs, is that the bolt must not carry the current, it merely provides clamping force to compress the copper parts and hold them very securely together. High tensile steel bolts are ideal for that function. The electrical current then flows directly between the copper parts.

I would not bolt one end of a fuse directly onto one of the battery terminals, any movement applies stresses the parts were not designed for.
Much better to bolt the standoff insulators to a rigid part of the metal battery frame, in a readily accessible location, and use a short length of flexible wiring between the last battery terminal and the fuse. Its also then possible to locate the fuse where metal tools are less likely to cause any shorts to ground when replacing the fuse.

Its not rocket science, but any electrical inspector will be looking for obvious points of danger, or potential failure. If its a well thought out, neat, and practical installation, the inspector is more likely to appreciate the thought and effort that went into it.

 

[mantonis]

Why not use a Bussmann marine fuse holder? I bolt those to a battery bank busbar and connect the individual batteries to the busbar through these fuses. I believe Deep Sea may stock these. I have bought my fuse holders through AliExpress but the fuses are genuine Bussmann.

 

[pekka8]

It's a good point that bolting mega fuse directly is pita to change. I ended up with those Blue Sea MRBF holders. Not so easy to get the fuses but maybe I'm not blowing them too often

 

[Ellcon123]

I prefer to minimise connections so bolting direct to fuse is my option. Fuses are an absolute last resort so if they are blowing I have bigger issues than replacing a fuse.

 

[Jet]

What kind of battery terminal. Is it a post? What size?

 

[Levo]

Not sure if this suits your particular situation, but I found this arrangement easy enough and cost effective (posted in an earlier thread):

I found the Blue Sea less available in Canada and therefore costly when adding US shipping. I bought this MRBF on Amazon.ca:
https://www.amazon.ca/Blue-Sea-Syst...01E4F3J4&psc=1&ref_=pd_bap_d_grid_rp_0_1_ec_i

Rather than use a manufactured mount I used a piece of solid copper which I sanded and polished perfectly flat. The picture shows a Bussman Z-case fuse, but the Blue Sea MRBF is now installed with the insulated bolt assembly. I was able to drill the 2 different size mounting holes exactly as required by the battery terminal and the fuse. I carry the Z-case as a spare.

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[douglasheld]

There are a couple simple products available, so that you can screw a MRBF directly onto a battery terminal. There is a straight-through design, and a 90˚ design:

• https://www.almsolutions.co.uk/index.php?main_page=product_info&products_id=1776
• https://www.12voltplanet.co.uk/single-fused-positive-battery-terminal-clamp-with-isolation-nut.html

Both of these, worryingly require an insulated nut and therefore, you know that threaded post is a live unfused electrode.

Whereas, with the more commonly available MRBF housings, the threaded post is insulated. That means, if a stray metal tool touches the post, it's going to get the fused circuit and blow the fuse which is what you want.

This is where I had it explained to me: