LFP Available Short Circuit Current

[sailingharry]

Originally Posted by more

if T-fuse good and reliable bee in all EU house,
simply NH is beter fuse capable.
T-fuse is rare used in EU very hard find,conclusion skip

Well....
If NH good and reliable would be recommended for all US boats, simply T is better fuse.
NH is rarely used in US very hard to find, conclusion skip.

Or maybe they are equally suitable and just different. Like finding straight pipe fittings in the US and tapered in Europe.

[Pete7]

Class T fuses are £47 from my favourite supplier and that's just fuse, not the holder. https://www.12voltplanet.co.uk/bussm...s-t-fuses.html

I went with MH fuses at half the price for a fuse and the holder.

Pete

[Statistical]

Originally Posted by sailingharry

Well....
If NH good and reliable would be recommended for all US boats, simply T is better fuse.
NH is rarely used in US very hard to find, conclusion skip.

Or maybe they are equally suitable and just different. Like finding straight pipe fittings in the US and tapered in Europe.

I would add that while class-T fuses are available with 10k AIC there are models that are also available with 20k and higher AIC.

Honestly if you have a battery bank capable of >10k A short circuit current probably makes more sense to break it into two smaller more managable batteries but fuses are available to handle even crazy large batteries.

[CaptainRivet]

Originally Posted by Statistical

I would add that while class-T fuses are available with 10k AIC there are models that are also available with 20k and higher AIC.

Honestly if you have a battery bank capable of >10k A short circuit current probably makes more sense to break it into two smaller more managable batteries but fuses are available to handle even crazy large batteries.

A main battery bank fuses the bank as a whole, if you split in several smaller it still needs to come together to a main busbar and there you need the big chunky one that can carry the total current, continious, peak and AIC of all together.
As you also need a disconnect switch the NH fises come in handy as you can simply pull the fuse and save yourself a disconnection switch.
And try to find one above 600A...NH4 goes till 1500A, NH3 till 630A.

NH and Class T are equal till a bank of 400-500AH 12V, above only NH is arcing save. Class T has the advantage its reacts faster so if you really cycle your bank hard with high C rates it can better safe your bank from overload. On the other side if you have a hybrid starter/house the class T acts too fast eqpecially if its in the range of 10 till 20% of ypir starters wattage means 2000W starter woth a 200-400A class T main fuse...if the starter needs to work extremly hard eg start with inbgear becausz gear is stuck the class T will blow, a NHbin GG or GL spec no but still porotect the bank fastvenough from a short or overload when chosen cotrectly. The class T would need ro be higher current rating whichbisbtoo high for a) overload protection and b) cell will get damaged in a short due to too high peak current reached before class T disconnects.

[Statistical]

Originally Posted by CaptainRivet

A main battery bank fuses the bank as a whole, if you split in several smaller it still needs to come together to a main busbar and there you need the big chunky one that can carry the total current, continious, peak and AIC of all together.

At the busbar the short circuit current will be lower because the battery cables add their own resistance. AIC requirements will be reduced.

NH and Class T are equal till a bank of 400-500AH 12V, above only NH is arcing save.

Again false. For very large batteries class T fuses. 50k AIC, 100k AIC, and even 200k AIC are available. Nothing wrong with NH fuses but they don't have these mythical one of a kind properties you make them out to have.

2000W starter woth a 200-400A class T main fuse...if the starter needs to work extremly hard eg start with inbgear becausz gear is stuck the class T will blow.

Properly sized it would not. You are a nonstop source of half truths superstitions and wives tales.

[CaptainRivet]

Originally Posted by Statistical

At the busbar the short circuit current will be lower because the battery cables add their own resistance. AIC requirements will be reduced.



Again false. For very large batteries class T fuses. 50k AIC, 100k AIC, and even 200k AIC are available. Nothing wrong with NH fuses but they don't have these mythical one of a kind properties you make them out to have.



Properly sized it would not. You are a nonstop source of half truths superstitions and wives tales.

There are no mysticals, its simply a requirement for grid station that eg a shortend transformator is .and stays isolated by the fuse and this trafo will continue to produce rising currents after the fuse blown, same does the LFP bank. The bank and grid station fuse just disconnects = tjats the AIC rating and has to stay disconnected= thats not AIC when the current rises and approaches the blown fuse over a longer time and ionizing the air, vhich has the consequence that arcing can happen much earlier then in one high peak. Means AIC of 20kA iq enough to blow fuse eg a 1200AH bank with 16000A short curcuit current possibilty but that this cutrent approches the fuse over several seconds is enough to ionize the air tjat 10000A can arc a gap of 3cm under bad circumstances, well a 400A class T has 7mm gap....a 400AH class NH3 has 8cm. To arc that 3cm in a short peak eg a lighting strike or the first current peak of a shortend bank you wouls need 8-10 times the current = 80-100kA and that is the AIC rating. Thats why a class T with 7mm can have a 20 or even a 40kA AIC rating.
And for this is simply a class T is not made and speced for because its physical size doesn't allow that, this is one reason class T is only avaliable in super fast acting, nothing else. And to reach this requirement you simply need a lot ceramic and physical distance=huge size of the fuse.
Thats all, nothing mystical.

[s/v Jedi]

Funny how people keep ignoring laws of nature (Ohm’s law to be precise) and regurgitating shoreside applications

[CaptainRivet]

Here is a official video from thundersky where they are testing a 40AH Winston cell.

https://m.youtube.com/watch?v=R9xZf4p8PkQ

At 1:06 you can see that this 40AH Winston cell created a short circuit up to 1600A, which is 400C…so how much short circuit current a 400AH or a 1000AH cell is creating…400AH 16000A and a 1000AH 40000A, well take away some for heat and higher resistance but 20000-30000A for one(!) 1000AH cell is realistic.

This to all that are telling these high currents are theoretical, no they are not as this test proofs.
You can also see how the current is building up and bloating and then gasing the cell, the fuse would have blown in the first second but the cell would be hitting the blown fuse with more and more current over more then 5 seconds.

and my shortend 400AH bank that arced a 400A blown class T was most likely not an installation mistake, it was just 10000A hitting a blown class T and arcing over the 7mm gap.

[CharlieJ]

At 1:06 you can see that this 40AH Winston cell created a short circuit up to 1600A, which is 400C…so how much short circuit current a 400AH or a 1000AH cell is creating…400AH 16000A and a 1000AH 40000A, well take away some for heat and higher resistance but 20000-30000A for one(!) 1000AH cell is realistic.

Correction: A 1600A short circuit produced by a 40Ah cell is 40C, not 400C!

[Statistical]

Originally Posted by CaptainRivet

Here is a official video from thundersky where they are testing a 40AH Winston cell.

At 1:06 you can see that this 40AH Winston cell created a short circuit up to 1600A, which is 400C…so how much short circuit current a 400AH or a 1000AH cell is creating…400AH 16000A and a 1000AH 40000A, well take away some for heat and higher resistance but 20000-30000A for one(!) 1000AH cell is realistic.

This to all that are telling these high currents are theoretical, no they are not as this test proofs.
You can also see how the current is building up and bloating and then gasing the cell, the fuse would have blown in the first second but the cell would be hitting the blown fuse with more and more current over more then 5 seconds.

and my shortend 400AH bank that arced a 400A blown class T was most likely not an installation mistake, it was just 10000A hitting a blown class T and arcing over the 7mm gap.

Or as other people have said you do the actual math. The 1,600A observed is less than the theoretical short circuit current from this cell. These 40Ah Winston cells have 0.7 mOhm internal resistance.

3.65V / (0.7/1000) = 5,214A peak short circuit current so about 3x what as observed.

Rather than try to guess one should DO THE MATH. If your battery has >20k short circuit current then use a fuse which has >20k AIC like a higher grade class T fuse (available in 50k & 100k AIC versions).

I really doubt someone is going to build a 400Ah pack using 10 of these 40 Ah cells in parallel but if they did they should have a fuse with >52,140 AIC.

Likewise if someone was building a really huge battery bank like say 48V 1000 Ah possibly for electric propulsion they probably should break that into 3 or 4 batteries each with their own BMS and fuse. I mean in theory you could make one giant battery in a 16S4P configuration using 250 Ah cells but that is probably dumb and there would be questions where you would put a single battery that large.

and my shortend 400AH bank that arced a 400A blown class T was most likely not an installation mistake, it was just 10000A hitting a blown class T and arcing over the 7mm gap.

That litterally is an installation/installer mistake. If you have a power source capable of 10,000A+ short circuit current and installed a fuse without sufficient AIC to safely handle that then that was a mistake. You should have used a fuse with correct AIC rating.

[GordMay]

Originally Posted by Statistical

... For very large batteries class T fuses. 50k AIC, 100k AIC, and even 200k AIC are available. .

Bussmann's Class T current-limiting, fast-acting fuses. Provides 10X better current limitation to help prevent equipment damage caused by short-circuit events. 200 kA* (AC only) Interrupting rating complies with NEC® Section 110.9 for today’s large capacity systems.
➥ https://www.eaton.com/us/en-us/catal...s-t-fuses.html

* IR
• 200kA Vac RMS Sym.
• 20kA Vdc (15-600 A)
• 100kA Vdc (700-1200 A)
➥ https://www.eaton.com/content/dam/ea...s-1025-jjn.pdf

[s/v Jedi]

Here, the superiority of class-T fuses demonstrated

https://www.youtube.com/watch?v=0mGhhdPgXG8

[CaptainRivet]

Originally Posted by Statistical

Or as other people have said you do the actual math. The 1,600A observed is less than the theoretical short circuit current from this cell. These 40Ah Winston cells have 0.7 mOhm internal resistance.

3.65V / (0.7/1000) = 5,214A peak short circuit current so about 3x what as observed.

Rather than try to guess one should DO THE MATH. If your battery has >20k short circuit current then use a fuse which has >20k AIC like a higher grade class T fuse (available in 50k & 100k AIC versions).

I really doubt someone is going to build a 400Ah pack using 10 of these 40 Ah cells in parallel but if they did they should have a fuse with >52,140 AIC.

Likewise if someone was building a really huge battery bank like say 48V 1000 Ah possibly for electric propulsion they probably should break that into 3 or 4 batteries each with their own BMS and fuse. I mean in theory you could make one giant battery in a 16S4P configuration using 250 Ah cells but that is probably dumb and there would be questions where you would put a single battery that large.



That litterally is an installation/installer mistake. If you have a power source capable of 10,000A+ short circuit current and installed a fuse without sufficient AIC to safely handle that then that was a mistake. You should have used a fuse with correct AIC rating.

Please read my post carefully again.
Again AIC is the first high current burst of a shortened bank and there the fuse blows correctly and done in my case as well. Popp the fuse, thats AIC rating.

But then the blown fuse gets approached by MORE current as it just disconnects the installation but cannot stop the shortened bank. This is NOT AIC rating anymore!!! As i said high current over time ionizes the air and that has consequence that arcing can happen much earlier then the AIC rating of the fuse.AIC rating is not the current the blown fuse can stand and KEEP disconnected of a longer periode of time. Class T is very bad at that due to the compact manufacturing. Thats also the reason they disconnect super fast.

[Statistical]

Originally Posted by CaptainRivet

Please read my post carefully again.
Again AIC is the first high current burst of a shortened bank and there the fuse blows correctly and done in my case as well. Popp the fuse, thats AIC rating.

But then the blown fuse gets approached by MORE current as it just disconnects the installation but cannot stop the shortened bank. This is NOT AIC rating anymore!!! As i said high current over time ionizes the air and that has consequence that arcing can happen much earlier then the AIC rating of the fuse.AIC rating is not the current the blown fuse can stand and KEEP disconnected of a longer periode of time. Class T is very bad at that due to the compact manufacturing. Thats also the reason they disconnect super fast.

Yeah none of that is correct. Not even close. Just mystical voodoo you made up in your mind.

[tanglewood]

Originally Posted by CaptainRivet

Please read my post carefully again.
Again AIC is the first high current burst of a shortened bank and there the fuse blows correctly and done in my case as well. Popp the fuse, thats AIC rating.

But then the blown fuse gets approached by MORE current as it just disconnects the installation but cannot stop the shortened bank. This is NOT AIC rating anymore!!! As i said high current over time ionizes the air and that has consequence that arcing can happen much earlier then the AIC rating of the fuse.AIC rating is not the current the blown fuse can stand and KEEP disconnected of a longer periode of time. Class T is very bad at that due to the compact manufacturing. Thats also the reason they disconnect super fast.

No, I think this is PRECISELY what the AIC rating is. It's the maximum current at which the fuse can open, and STAY open. I think the discussion has been going in circles for nearly a month because you are working to an incorrect definition of what AIC means/is.