Fuse directly on battery terminal

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syvictoria

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Hi. Given insufficient height to install an MRBF fuse, are there any other fuses that can safely be installed directly on the battery terminal (8mm stud)? It seems sensible to remove one additional connection (battery to fuse holder) if possible. Engine is a diesel. Thanks very much!
 
Wow, that was quick! Thanks. That wouldn't fit the battery terminal as-is, but I think I've seen adaptors. The terminal is currently an 8mm stud (Trojan battery).
 
syvictoria said:
Wow, that was quick! Thanks. That wouldn't fit the battery terminal as-is, but I think I've seen adaptors. The terminal is currently an 8mm stud (Trojan battery).
Click to expand...

I've wondered about fitting the fuse directly onto the 8mm stud, but not got around to trying one yet. The problem is, the nylon isolator that comes with the battery clamp is not available separately, or i haven't found one yet. If it was, i'm sure it would work fine. Wouldn't take much to turn one on a lathe, it's just a top hat shaped piece of nylon, 8mm ID, 10mm ID at the narrow end and about 16mm at the wider end, around 10mm long in total. It's just to isolated the 8mm stud from the centre of the fuse.
 
I can see some advantages in the fuse mounted on a battery post, but (certainly with lead acid batteries anyway) its not the place I would want a red hot piece of metal about to vaporise when the fuse blows.
edit- in the event of a dead short!
 
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PaulRainbow said:
I've wondered about fitting the fuse directly onto the 8mm stud, but not got around to trying one yet. The problem is, the nylon isolator that comes with the battery clamp is not available separately, or i haven't found one yet. If it was, i'm sure it would work fine. Wouldn't take much to turn one on a lathe, it's just a top hat shaped piece of nylon, 8mm ID, 10mm ID at the narrow end and about 16mm at the wider end, around 10mm long in total. It's just to isolated the 8mm stud from the centre of the fuse.
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These any good ?
uk.rs-online.com/web/c/fasteners-fixings/spacers-standoffs/screw-insulators/
 
I actively hack those out of boats :eek:

Try finding a spare fuse for one of those in the local chandlery on a Sunday after you've blown the spare you already cable tied to the cable, in case the first blew.

Horrible nasty things. Of course the first thing someone does when a fuse blows is to put another one in to see what happened! Alright if you keep a handful on board and discipline yourself to order more if ever the stockpile became short, but just not nice :disgust:
 
matthewriches said:
I actively hack those out of boats :eek:

Try finding a spare fuse for one of those in the local chandlery on a Sunday after you've blown the spare you already cable tied to the cable, in case the first blew.

Horrible nasty things. Of course the first thing someone does when a fuse blows is to put another one in to see what happened! Alright if you keep a handful on board and discipline yourself to order more if ever the stockpile became short, but just not nice :disgust:
Click to expand...

You could apply that logic to any fuse, anywhere. Unles you're fitting circuit breakers, fuses will blow and you need spares. Circuit breakers rated for starter circuits would likely cost more than most people here would be prepared to pay. If you had an issue that blew a cube fuse and didn't have a spare, it's pretty easy to get around, just move the isolating spacer the other side of the cable lug (once the fault has been fixed).
 
zoidberg said:
Would this Isolator Switch ( https://www.12voltplanet.co.uk/marine-battery-isolator-switch-2-positions.html ) be thought suitable for isolation of a starter battery, should there be a fault? Or would this simpler Isolation Key ( https://www.12voltplanet.co.uk/battery-isolator-switch-removeable-key.html ) be just as suitable? The 35mm starter cables are each < 1 metre.

Cube fuses or mega fuses? Ratings?
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First one is better.

Cube fuse or mega fuse, your choice. Cube fuse is easy to fit, straight onto special battery terminal, mega fuse requires interconnecting cabling, i'd go cube fuse. Rating should be higher than max load but lower than cable rating, 35mm cables = 240amp, so fit a 240 amp fuse, 50mm cable takes more current, but is usually fitted to overcome voltage drop (on the small boats we are talking about here), so a 240amp fuse is still applicable.
 
Apologies for resurrecting an old thread, but I've only just got round to thinking about this again... Could a meagfuse be mounted directly on a battery terminal (thread type, 8mm), again with the aim being to minimise connections and cabling? I appreciate that the other end would need to be supported on a post or similar (or maybe a megafuse holder could be adapted?). Thanks!
 
Wouldn’t be a great idea. But never say never.

In that case best just get a terminal mounted fuse box.

syvictoria said:
Apologies for resurrecting an old thread, but I've only just got round to thinking about this again... Could a meagfuse be mounted directly on a battery terminal (thread type, 8mm), again with the aim being to minimise connections and cabling? I appreciate that the other end would need to be supported on a post or similar (or maybe a megafuse holder could be adapted?). Thanks!
Click to expand...
 
Would this be of any use?

terminal-fuse-block.png


http://www.rjsmarine.co.uk/5191-mrbf-terminal-fuse-block-30-to-300a
 
I'm bringing this thread back for it's third round! Has anyone had a chance to come up with any further solutions for this over the winter? Thanks!
 
I'm currently re-doing the battery wiring on my boat, and I've opted for the cube fuses linked to at the start of the thread.

You can argue for and against almost any of the possible options, but my rationale is that these mean the cable is fused right from the battery, and I don't have to run extra cable to somewhere suitable to mount a link/mega/whatever fuse (not so obvious on a sleek 80s sailboat, we don't all have big engine rooms!).

I'm not currently planning on fusing the cable from the cranking battery, but I might even change my mind on that.
 
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