Battery Post Fuses!

[Dougal]

Anyone got any thoughts or experience with these for marine use? My batteries are all inside, tucked away nice and warm;-)
http://www.autoelectricsupplies.co.uk/product/1024/category/192#flash-msg

 

[FWB]

Won't the alternator be damaged if the fuse blows with the engine running?

 

[ghostlymoron]

They look a neat solution from what I can make out. No more risky than any other battery fuse IMHO. Mind you, I've never fitted one of those either.

 

[RichardS]

Won't the alternator be damaged if the fuse blows with the engine running?

I think that's true but surely the same applies wherever you insert the fuse in the battery cable?

Richard

 

[FWB]

I think that's true but surely the same applies wherever you insert the fuse in the battery cable?

Richard

Why would you want to put a fuse in the battery cable? Why run the risk of damaging the alternator?

 

[prv]

Why would you want to put a fuse in the battery cable?

So that it doesn't turn into a welding electrode when it chafes through the insulation, becomes detached from its terminal, or otherwise makes contact with the engine.

Why run the risk of damaging the alternator?

Because it's better than setting the boat on fire? A 100amp fuse isn't going to "just blow" and damage your rectifier diodes for no reason; if it pops then something serious is already under way.

Pete

 

[yachtorion]

Blue Sea do a marine version, "Marine Rated Battery Fuse" - https://www.bluesea.com/products/5191/MRBF_Terminal_Fuse_Block_-_30_to_300A

The friendly forumite that you would expect to sell bits of boat electronics, alongside the heaters, does. And for a good price.

 

[FWB]

So that it doesn't turn into a welding electrode when it chafes through the insulation, becomes detached from its terminal, or otherwise makes contact with the
Because it's better than setting the boat on fire? A 100amp fuse isn't going to "just blow" and damage your rectifier diodes for no reason; if it pops then something serious is already under way.

Pete

You must have a poor installation.

 

[Norman_E]

I don't like the idea of any fuse being in the same compartment as a battery. The battery may well be gassing before the fuse blows, with the resultant explosion risk. I think those fuses are sealed, but who knows if the seal will be effective? In any case I see no reason to fuse the battery leads. Just make sure that they are securely crimped and securely clamped at both ends, and make sure they are not getting chafed and don't run the positive lead close to any earthed metal. My big 25mm and 35 mm battery charger cables need fuses, but these are mounted at the charger end, well away from the batteries.

 

[Dougal]

We don't (yet!) have fuses or breakers on either our main battery or charging cables. I HAVE though, personally witnessed what happened to a power boat, on it's maiden launch no less, when the starter jammed on... The whole boat was destroyed in less than 5 minuites!

I've also seen other electrical fires, started from unprotected H/D wiring.

I'm sort of leaning towards fitting breakers.

 

[prv]

You must have a poor installation.

I don't quite know what to make of that.

Pete

 

[FWB]

I don't quite know what to make of that.

Pete

Just remarking that it appears that you think your set up is likely to fail.
By putting a fuse in the line you are allowing automatic battery switching off....something you would never do manually....unless you had a supply of spare alternators onboard.

 

[prv]

In any case I see no reason to fuse the battery leads. Just make sure that they are securely crimped and securely clamped at both ends, and make sure they are not getting chafed and don't run the positive lead close to any earthed metal.

How do you propose to connect it to the starter motor without bringing it anywhere near the engine?

My big 25mm and 35 mm battery charger cables need fuses, but these are mounted at the charger end, well away from the batteries.

Why do these cables need fuses yet the others do not?

Pete

 

[prv]

Just remarking that it appears that you think your set up is likely to fail.

Apparently so you do. Why else would you be worrying about your alternator?

Pete

 

[prv]

By putting a fuse in the line you are allowing automatic battery switching off....something you would never do manually....unless you had a supply of spare alternators onboard.

And under what circumstances do you believe this would happen?

Pete

 

[FWB]

And under what circumstances do you believe this would happen?

Pete

If you don't think it would happen then why fit a fuse?
You answered that in your post #6

 

[prv]

If you don't think it would happen then why fit a fuse?

The fuse is there just in case there's ever a substantial short between positive and negative through 50mm² cables. A new rectifier (if the engine happens to be running hard at the time, which odds are it isn't) is preferable to emptying 450 amp-hours through that short in a matter of seconds and potentially losing the boat - see post #10.

The rest of the time, both fuse and alternator are perfectly happy and I don't understand why you think there's a problem.

Pete

 

[FWB]

The fuse is there just in case there's ever a substantial short between positive and negative through 50mm² cables. A new rectifier (if the engine happens to be running hard at the time, which odds are it isn't) is preferable to emptying 450 amp-hours through that short in a matter of seconds and potentially losing the boat - see post #10.

The rest of the time, both fuse and alternator are perfectly happy and I don't understand why you think there's a problem.

Pete

I don't have a problem which is why I don't have a fuse.
Hey, this is just friendly banter

 

[prv]

I don't think there's a problem which is why I don't have a fuse.

In both post #5 and post #12 you said you don't have a fuse because you're concerned about your alternator. Further, you implied that other people shouldn't have fuses because of the risk to their alternators.

Hey, this is hopefully friendly banter.

Frankly I didn't appreciate post #8. But I'm willing to shake hands...

Pete

 

[FWB]

In both post #5 and post #12 you said you don't have a fuse because you're concerned about your alternator.

Pete

I'm not concerned about my alternator because the battery is not going to switch itself off.
I'm concerned about your alternator.