High capacity DC breakers

[fredrussell]

Double post.

 

[fredrussell]

But isn't that just a forum post by some random bloke ?

The general thinking is that Class T or NH fuses are best practice. Even the best midi fuses only have an AIC of 5000A with a max current of 200A. Again, it's stuff like this that makes insurance companies insist on pro installs.

No, have a good read of it. Op seems to be very knowledgeable in this area, and has the equipment to provide actual figures. It’s a long and tedious thread I’ll admit, but what I take from it is that the American boating authority has picked a class T fuse as the best fuse because it’s good enough for pretty much any size battery bank one is likely to have on a boat. But if your battery bank is a ‘smaller’ one, you can use certain other fuses such as MRBF safely.

 

[Sea Change]

Not so much promoting them as saying I like the fact that they eliminate an un-fused length of cable between terminal and fuse. I fitted an MRBF to my 280ah battery after reading the CF thread below on AIC which suggests that MRBF are perfectly adequate for my setup. Unless I misunderstand what they’re saying a 280ah LiFePo battery will not exceed the AIC rating of my MRBF fuse.

https://www.cruisersforum.com/forums/f166/lithium-short-circuit-current-aic-298934.html

Edit: The thread above is a long one, so here’s part of the OP’s summary, based on tests he did:
…”For 12/24V systems up to 200Ah, AMI/MIDI, MRBF, ANL and class-T fuses are acceptable. Above 200Ah, only MRBF, ANL and class-T fuses are acceptable.

For 48V systems up to 200Ah, MRBF, ANL and class-T fuses are acceptable. Above 200Ah only ANL and class-T fuses are acceptable.”

I'm surprised he rates ANL so highly. I haven't come across any figures that suggest they are as high AIC as MRBF.

 

[Sea Change]

In the UK I can get them , depending on size for well under £50 - up to 200 amp retail at £33 and up to 500a £49
BEP or BlueSeas holders at £30 each
For multi battery systems there are bulk discounts as well
Not sure with the US tariff situation now how de minimus would work but if you're happy with shipping costs I'm happy to get you some here and post them over if the figures work for you

Thanks, that's about the price I was expecting and indeed similar to what I was paying four or five years ago.
Shipping to the US sends pretty risky at the moment, however I'm thinking of sending over some NH fuses as they're about £5 a go so I'd they get impounded it's no great loss. They're very hard to get hold of over there.

Seeing as I'm moving to a four battery setup, spending £100 on a fuse and holder for each battery really adds up...

 

[PaulRainbow]

No, have a good read of it. Op seems to be very knowledgeable in this area, and has the equipment to provide actual figures. It’s a long and tedious thread I’ll admit, but what I take from it is that the American boating authority has picked a class T fuse as the best fuse because it’s good enough for pretty much any size battery bank one is likely to have on a boat. But if your battery bank is a ‘smaller’ one, you can use certain other fuses such as MRBF safely.

Sorry but i don't have the time or inclination to read long forum posts by random blokes. If you want to follow his advice rather than go by that of established best practice that's up to you.

Personally, although i'm not obliged to do so, i follow the ABYC guidelines as much as possible. If i'm asked by an insurance company for details/specs of an install i can provide acceptable details to them.

This is a perfect example of why insurance companies don't want DIY installs.

 

[fredrussell]

Sorry but i don't have the time or inclination to read long forum posts by random blokes. If you want to follow his advice rather than go by that of established best practice that's up to you.

Well, fair enough then. Will Prowse is some random bloke of the internet but we all seem to accept that he’s put in the hard work and not just plucking facts and figures from thin air. This being a relatively new field I think it’s a question of trying to work out which sources of info can be trusted. The one I linked to seems to me to have also done the hard work and provided proof of that. I totally accept and understand that as a professional you have to go by the official recommendation, which, in the absence of any UK ‘legislation’, is that of the ABYC.

 

[Sea Change]

I'm not a big fan of 'just get a professional to do it'. As far as I'm aware, anybody can call themselves a marine electrician. I've seen a 'pro' lithium installation protected only by an ANL fuse. Another where tens of thousands of dollars had been spent and Victron components were melting (don't try to run 1000A at 12v ).

I suspect I'm similar to most Practical Boat Owners in that I like to fully understand all of the systems on my boat, and do most of the work myself.

There are good professionals, and there are cowboys. We're lucky to have people like Paul on here who knows what he's doing and is willing to share his knowledge. Picking his brains is part of what I consider due diligence. But just because I'm asking about a certain way of doing something doesn't mean I'm endorsing it.

By the way, I asked about these breakers on a Facebook group, and somebody posted a video where a German guy was putting them through their paces. The 160A breaker ran for over an hour at 250A, and even at 350A took over three minutes to blow.

So, that's a no from me.