I think we are aligned in terms of wanting to decide based on facts. I appreciate the theoretical calculations but are there facts that would make the theoretical values you got not to be attainable? Like empirical evidence. Like other theoretical constraints. With all the technical capacity Victron's has, Victron still recommends (and sells) Mega / CNN/ ANL fuses which have lower AIC rating than the T fuses. Shouldn't there be a reason for that? Regards
Class T vs ANL fuse
- Thread starter MarvRVHam
- Start date
Does Victron offer LiFePo4 batteries? If yes - with what fuses? If not - the fuses they offer are to protect their components and they likely expect a battery with proper protection. ANL fuses are perfectly good for lead-acid batteries. But I would not trust them for LiFePo4 battery. Better safe than sorry 
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.Yes, Victron offers LiFePO4 batteries. And yes, they recommend Mega / CNN/ ANL fuses. See attached standard Victron drawing downloaded from Victron website.Does Victron offer LiFePo4 batteries? If yes - with what fuses? If not - the fuses they offer are to protect their components and they likely expect a battery with proper protection. ANL fuses are perfectly good for lead-acid batteries. But I would not trust them for LiFePo4 battery. Better safe than sorry
FilterGuy
Solar Engineering Consultant - EG4 and Consumers
I have talked to a few Victron representatives and a Victron Ambassador and they all say the mega-fuse is not enough for even their own LiFePO4 batteries.
One said you could do a MRBF (10KA AIC) on a single LiFePO4 and a Class T for parallel LiFePO4s. The others said to Always use Class T.
This surprises and disappoints me. Victron does a really good job of taking a system approach to all of their components.... but they seem to have missed the boat on this. The Lynx system is really slick but to use it with proper fusing you pretty much have to add a wart to it.
One said you could do a MRBF (10KA AIC) on a single LiFePO4 and a Class T for parallel LiFePO4s. The others said to Always use Class T.
This surprises and disappoints me. Victron does a really good job of taking a system approach to all of their components.... but they seem to have missed the boat on this. The Lynx system is really slick but to use it with proper fusing you pretty much have to add a wart to it.
Interesting experiment involving blowing stuff up using a bank of 100 lead acid car batteries! Currents are in the tens of thousands of Amps. He actually tests a standard home circuit breaker at 26min and it performs surprisingly well.
FilterGuy
Solar Engineering Consultant - EG4 and Consumers
I remember when I was that young and thought I could never get hurt. The fact that young boys grow up to be adults is proof there are guardian angels.
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That bullet proof attitude is what built this country… damn the torpedoes ..straight ahead.
12VoltInstalls
life passes by too quickly to not live in freedom
There was a lot more wisdom in young men and women than you are giving them credit for. They observed more and strategized better. Women didn’t have to prove anything, either, they just did what was necessary in the moment like Hannah Dustin; that they were different than men didn’t make them better or inadequate. And young men were competent and capable by 16, and were happy to apprentice themselves and become something. Maturity wasn’t postponed and they didn’t tolerate a lack of industriousness- probably partially due to being responsible was directly correlated with eating, being warm and dry, and becoming something by the time they were 20 years old. Heck, even more recently EB White was considered to have peaked in competency by 29 years old but today that level of respect isn’t afforded until someone’s in their 40’s.
Youthful vigor was productive and expected; you can’t inspect the culture of 250 years ago with the lens of today and expect an accurate evaluation. While risk taking is a component of youthful vigor one cannot define define ‘grit’ totally within the subset of “bullet proof attitude,” and those that “built this country” were much more proficient in wisdom than “grit.” Combine the two, however, and it’s a powerful force. That’s the essential difference between a Green Beret and the rank-and-file soldier today, for example.
Oddly , it seems my message was misunderstood …we’re are saying and praising EXACTLY the same thing in the quality of the people of the past .
it’s not as easy to say in as few a words all the conditions which you say in your definition .. but trust me we are in agreement…
sometimes words get read differently than they were written…
I witnessed of what I speak, as an aware young boy going back to the mid 1950s..
I firsthand saw how my dad and grandad and great grand dad handled life ,the family and adverse conditions… from Alabama to Washington DC to Florida…I also saw how my mother and grandma handled life… first hand …in person… they all did a wonderfull job…. some were farmers and some were politicians , some were Drs…..some raised the many children…all worked dawn to dusk…that was just life for most back then…
they were strong , good and hard working people…family ,country and ones religious belief always came first in their life’s descions…they stood for principles , and they weren’t afraid to say it.
sorry if my torpedos comment didn’t convey all that properly..
J.
Boron
New Member
you didnt try your test in open air, dropped in a bucket (for safety i guess)
Boron
New Member
AFAIK the convention (code?) is that a fuse link is the last line of defense? All house have that system - a main utility cartridge fuse sealed by the Utility Company (100A) then you got to the board with the main mcb breaker plus all the branch cct mcbs etc.
BTW I noticed on Fleabay that unscrupulous vendors from ykw are offering Solar 40A disconnect switches that look like mcb's. These are certainly not for breaking under load and could cause an Arcflash event. These are nothing more than beefed up light switches. Be warned.
Boron
New Member
FWIW I offer this gem I found http://cmte.ieee.org/pes-essb/wp-co...al-Concepts-and-Standards-R-Veeraraghavan.pdf
Its taken from some very credible research work by leading authorities on dc Arc flash issues.
My take on this is that an arc will self extinguish when the gap resistance/cooling effect is greater than the applied voltage x fault current. So I think that a 20mm (or inch) gap to break a 24v circuit is pretty much bomb proof (well over the 20,000A vendors like to quote).
48v may need twice the gap - see for your self - its not my system interest.
So you could break the circuit with a knife switch (like Frankenstein) because the gap will be ca 50mm or more (I would wear gloves BTW cos it will flash momentarily.
Those travelling fairground operators used dc dynamos for their dc motors (bumper cars 24vdc, fairground rides) cos they could repurpose dc traction motors which were easy for speed control and starting current etc. The Gen Sets had boards with knife switches.
Its taken from some very credible research work by leading authorities on dc Arc flash issues.
My take on this is that an arc will self extinguish when the gap resistance/cooling effect is greater than the applied voltage x fault current. So I think that a 20mm (or inch) gap to break a 24v circuit is pretty much bomb proof (well over the 20,000A vendors like to quote).
48v may need twice the gap - see for your self - its not my system interest.
So you could break the circuit with a knife switch (like Frankenstein) because the gap will be ca 50mm or more (I would wear gloves BTW cos it will flash momentarily.
Those travelling fairground operators used dc dynamos for their dc motors (bumper cars 24vdc, fairground rides) cos they could repurpose dc traction motors which were easy for speed control and starting current etc. The Gen Sets had boards with knife switches.
ERobertS
New Member
I've had much the same questions about using Class-T fuses. My take is they are needed for 48 volt LiFePO4 battery banks where the higher voltage creates a possible issue with internal fuse arcing which extends short disconnect time creating many dangers. The Class T fuse contains an arc inhibitor substance around the fusing element. ANL and Mega fuses having just a fusing element work well for the 12, 24 volts systems and are much easier to source. This concept driving the need for Class T comes down to high current DC arc physics where a higher voltage adds more energy to create an arc when the fusing element blows. I guess I can buy this explanation so I'm definitely going to add a Class T fuse for my next 48 Volt LiFePO4 battery project where I can depend upon the disconnect time. Wish I had a better idea of the risk of a typical inverter creating a dead short. Not liking the Class T cost or lead times.
robbob2112
Doing more research, mosty harmless
One other tidbit for you - the resistance of a class T verse a ANL/Mega/ANN fuse is less. I don't have any Mega fuses laying around or I would measure one. That tiny amount of extra resistance turns into a lot of excess heat. I have an ANL that I used with a 12v/2000w inverter and it gets considerably hotter. Going to do a test in a couple of weekends when I have time and see how much the resistance goes up as the different types of fuses heat.
all values in ohms - 4 wire 1035+ meter
Class T 300a = 0.00025
Class T 200a = 0.00040
ANL 250a = 0.00054
MRBF 200a = 0.00043
The jury is still out on the actual cause, but seems to be a tossup between the mega fuse melting and catching fire because of an arc after it blew and something to do with the battery bank.
hwy17
Anti-Solar Enthusiast
Blue Sea's Class T are rebranded from good manufacturers, like Littelfuse, and they are on Amazon at competitive pricing.
robbob2112
Doing more research, mosty harmless
I've actually been getting them considerably cheaper from https://powerwerx.com/ or mouser cheaper than from amazon. And they are all real that way verse a good fake.
hwy17
Anti-Solar Enthusiast
Yeah I browse Digikey often but I've always been frustrated trying to find Class T on there. I'm not personally concerned about fake Class T fuses I don't think those exist.
DPC
Solar Enthusiast
How are you measuring that?
Also 7 watts self heating at full load 2000w inverter.
Not sure of that is significant.
I was trained to touch everything during inspections.
I know some fuses get hot, lots of things get hot, but unless things are surprising me with heat I generally don't worry about it.
I cant quantify surprise in deg C or F
Now I watch the young electricians do inspections they do nit touch stuff.
They have been trained to be wary of arc flash and contact with live equipment.
I am also trained in the same safety systems but I turn stuff off and lock it out before I touch it
