What do our experts think of this of this?

GMLS · 2025-01-25T22:18:53+0000

Not seen this referenced anywhere else.
Just pushing anothet product?

PaulC70 · 2025-01-25T22:24:16+0000

dunno, are you going to make us all click on the click bait or tell us what the potential snake oil is she's on about?

Figaro · 2025-01-25T22:39:28+0000

Just watched it myself before coming on here, interesting and worth a watch.
No idea if it's strictly necessary but interested to know what others think

bigtwin · 2025-01-25T22:46:57+0000

Some insight into what it is might stimulate some responses/debate.
I’m never minded to respond to click bait YouTube videos.

Ian

olley · 2025-01-25T23:01:17+0000

He's saying that standard fuses aren't good enough as the main fuse on your battery, it needs to be a class C fuse.
Maybe Lenny HB can comment
Apparently ordinary mega fuses under a dead short of the battery, can weld themselves back together after blowing.

LithiumConvert · 2025-01-25T23:12:41+0000

Do our LiFePO4 batteries not have a BMS which will handle this problem?

GMLS · 2025-01-25T23:46:13+0000

olley said:
He's saying that standard fuses aren't good enough as the main fuse on your battery, it needs to be a class C fuse.
Maybe Lenny HB can comment
Apparently ordinary mega fuses under a dead short of the battery, can weld themselves back together after blowing.

Yup.I've got a terminal fuse on my Fogstar, then an isolation switch before the rest of the fuses.If a mega fuse can re establish itself I'd imagine a terminal fuse could as well.

GMLS · 2025-01-25T23:47:43+0000

bigtwin said:
Some insight into what it is might stimulate some responses/debate.
I’m never minded to respond to click bait YouTube videos.

Ian

Basically questionning whether mega fuses are the best option

jongood · 2025-01-26T06:41:03+0000

The presentation is awful, and the section of a van exploding is just sensationalist. I'm no expert but I think at 12 volts, most systems would be more than adequately protected by a decent quality terminal fuse.

bigtwin · 2025-01-26T07:37:37+0000

olley said:
Apparently ordinary mega fuses under a dead short of the battery, can weld themselves back together after blowing.

Yes, they can. That’s why MRBF or T Class are recommended for LiFePO4 batteries.

LithiumConvert said:
Do our LiFePO4 batteries not have a BMS which will handle this proble

They do, but that isn’t their purpose.

GMLS said:
Yup.I've got a terminal fuse on my Fogstar, then an isolation switch before the rest of the fuses.

Ditto

GMLS said:
If a mega fuse can re establish itself I'd imagine a terminal fuse could as well.

They might but they have a much higher interrupt capacity so it’s unlikely.

GMLS said:
Basically questionning whether mega fuses are the best option

They’re not appropriate at all.

Ian

Ray-Vic · 2025-01-26T09:24:52+0000

I (now) have MRBF terminal fuses on each of my Fogstar's, which are easier to fit/use and definitely a better option in my opinion, but I do still think this guy is being a little sensationalist in showing a van blowing up etc. This video explains it much clearer and identifies why the ICC of the fuse is so important, and what state they adopt when they fail.

I'm not so sure that the figure of 99.9% of people using the wrong fuses as quoted by the first guy is necessarily true, but I have seen an awful lot of systems on here with Mega fuses on the batteries.

If real world evidence is needed, below is my personal experience of what can happen when you have a short circuit whilst using a correctly 'rated' (genuine) Mega fuse on lithium batteries. Not ideal and a big learning curve. I was annoyed at myself as I originally had ANL fuses, which were fine, and swapped them out for Mega simply because I preferred the holders!

MisterB · 2025-01-26T09:33:44+0000

Can anyone recommend what size MRBF fuse would I need for a 304ah Fogstar please?

I have a 3000w Renogy inverter aswell ...

Thanks

Cush · 2025-01-26T09:39:02+0000

Ray-Vic said:
I (now) have MRBF terminal fuses on each of my Fogstar's, which are easier to fit/use and definitely a better option in my opinion, but I do still think this guy is being a little sensationalist in showing a van blowing up etc. This video explains it much clearer and identifies why the ICC of the fuse is so important, and what state they adopt when they fail.

Thanks for the video link

jongood · 2025-01-26T09:39:15+0000

MisterB said:
Can anyone recommend what size MRBF fuse would I need for a 304ah Fogstar please?

I have a 3000w Renogy inverter aswell ...

Thanks

I would have a look and see what manufacturer recommends

Ray-Vic · 2025-01-26T09:56:23+0000

MisterB said:
Can anyone recommend what size MRBF fuse would I need for a 304ah Fogstar please?

I have a 3000w Renogy inverter aswell ...

Thanks

The maximum rated output of the battery is 250a, so a fuse of 300a is fine, and this is the limit of the holders if using Blue Sea ones. Naturally your cables must also be rated to carry this current.

tacr2man · 2025-01-26T10:28:45+0000

https://www.electricalhub.com/media/catalog/product/pdfs/3080/fuse_blocks_blue_sea.pdf

might be of interest .

growly_bear · 2025-01-26T10:39:54+0000

Remember that the current rating of the fuse is its continuous rating and not its blow value. There are charts such as the one in the attachment which shows the current values and times taken to blow which should be considered. The attachment is for the Bussman MRBF fuse. A 300A fuse will not start to blow until around 390A and then only after 16 minutes! Obviously in a dead short situation current values are much higher and blow times are much faster

Busman terminal_fuse_delay_175-300A (1).webp

Cush · 2025-01-26T11:18:49+0000

tacr2man said:
https://www.electricalhub.com/media/catalog/product/pdfs/3080/fuse_blocks_blue_sea.pdf
might be of interest .

Really useful pdf. Thank you.

Ray-Vic · 2025-01-26T12:07:00+0000

tacr2man said:
https://www.electricalhub.com/media/catalog/product/pdfs/3080/fuse_blocks_blue_sea.pdf
might be of interest .

I've just checked mine as I didn't recall seeing a fibre washer and it seems they've changed the design since this document. The bolt is now actually isolated from the plate at the bottom so there is no need for the fibre washer at the top.

Very clever design and a bit of a relief.

BouncyBoatFolk · 2025-01-26T13:39:35+0000

Ray-Vic said:
I (now) have MRBF terminal fuses on each of my Fogstar's, which are easier to fit/use and definitely a better option in my opinion, but I do still think this guy is being a little sensationalist in showing a van blowing up etc. This video explains it much clearer and identifies why the ICC of the fuse is so important, and what state they adopt when they fail.

I'm not so sure that the figure of 99.9% of people using the wrong fuses as quoted by the first guy is necessarily true, but I have seen an awful lot of systems on here with Mega fuses on the batteries.

If real world evidence is needed, below is my personal experience of what can happen when you have a short circuit whilst using a correctly 'rated' (genuine) Mega fuse on lithium batteries. Not ideal and a big learning curve. I was annoyed at myself as I originally had ANL fuses, which were fine, and swapped them out for Mega simply because I preferred the holders!

View attachment 1004831

Any idea how much cumulative power you were pulling through that fuse? Just out of curiosity.
Mike.

Ray-Vic · 2025-01-26T15:36:52+0000

BouncyBoatFolk said:
Any idea how much cumulative power you were pulling through that fuse? Just out of curiosity.
Mike.

I don't know, but certainly more than enough to blow the fuse so can only assume it had bridged. Judging by the way the scorch marks are I believe this is what happened.

Raul · 2025-01-26T15:42:02+0000

LithiumConvert said:
Do our LiFePO4 batteries not have a BMS which will handle this problem?

No, semiconductors switching is not capable to deal with kA of shor circuit or fault current, you need a fuse that is capable of few kA.
Mega fuses top at just under 2kA, enough on small battery, but not on large parallel lithiums.

Raul · 2025-01-26T15:46:15+0000

MisterB said:
Can anyone recommend what size MRBF fuse would I need for a 304ah Fogstar please?

I have a 3000w Renogy inverter aswell ...

Thanks

What size cable?

Raul · 2025-01-26T16:17:03+0000

I have mentioned this in the past, some did understood the issue, and some took the piss of me. Here is a case that made me change every mega fuse on every lithium.

A Dutch couple in Netherlands went to the local victron dealer and purchased almost an entire system, less the batteries. About 3 years in, a battery developed a fault in the middle of the night, family managed to get to safety, while their new built house burnt down. Fire brigade put most of the fire out, identified the source and the offending mega fuse, with the famous name on it. One out of 5 fuses, if I remember, did not open on faulty battery, re fused and started a fire.
MisterB , you might came across this tread on DIY forum where we dip in and out about the Seplos bms. It was a Dutch gentleman that had a 100 plus pages tread, documenting about his saga.

Another personal case, I built a battery for my neighbour, off grid with a 5kva multiplus. I fitted a 250A class T fuse at the end of the battery. About 3 months later he has no power, fuse blew, inverter sustaining a 9kw overload for too long. His wife forgot the oven and decided to wash cook and hot water in the same time. I was shocked to se a 250A fuse at 51.2v blow by a 5kva multiplus overloaded. A mega would have carried on till cable insulation went on fire.

Whether this is less likely to happen at 12v, I'm not so sure: because the ark spacing for a 32v mega fuse is 1/4 to the space of a 58v mega fuse. I use Outback DC breakers rated at 10kA and sometime class T fuse, if, it is out of my control, like my neighbour. Horses for courses.

MisterB · 2025-01-26T16:42:04+0000

Thanks Raul I obviously need to change the fusing arrangement in the Moho and potentially the outside utility at home.

So a 250A T Class fuse for home?

MisterB · 2025-01-26T16:43:56+0000

Raul said:
What size cable?

35mm about 600mm in length

Raul · 2025-01-26T16:54:39+0000

MisterB said:
Thanks Raul I obviously need to change the fusing arrangement in the Moho and potentially the outside utility at home.

So a 250A T Class fuse for home?

Just don't copy me with the 250A. That was on a 50mm2 cable and was meant not to blow, but for an worst case scenario. Since then, I did change that to a 125A dc breaker. The multiplus at max chat only needs 100A.

MisterB · 2025-01-26T16:56:50+0000

Raul

so 125A DC breaker at home? i think i ordered a breaker a week or so ago, i just need to check what it is!

in the motorhome a 100A or 150A?

Raul · 2025-01-26T17:00:34+0000

MisterB said:
35mm about 600mm in length

Cable to small for a 12.8v to 3000w, add another one and fuse with 250A.

MisterB · 2025-01-26T17:01:54+0000

Raul said:
Cable to small for a 12.8v to 3000w, add another one and fuse with 250A.

or just up the cable to 50mm?

What do our experts think of this of this?

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