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Class T vs ANL fuse

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I can test modest size breakers for slow and fast trip on AC. I wire a resistive load in series with transformer primary, use breaker to short secondary. That boosts current (and reduces the voltage it interrupts. Could do same with fuses. I use one or more electric radiator heaters, one of them fed from variac, so I can dial in any current I want.

I might be able to scale this up to 1000A or so, enough to fast-trip a 200A breaker.
It would not test the characteristics of tripping at 20,000A or so, where class-T fuses stand out, or full voltage.

For fuses, it would be interesting to send a single pulse, timed with a triac to some point in AC sine wave. This could be below the onset of melt but would show resistance increase with time. That is likely a good way to spot outliers vs. authentic fuses. It could be a non-destructive test of fuses.

Midnight Solar described testing DC breakers with a string of car batteries. Enough series/parallel could test the fuses, but would cost more than buying fuses from approve suppliers.

Testing fast and slow blow times on AC would be a good start. String of batteries could also fast-blow the fuse with DC. One of the members (UpNorth?) tested lithium battery shorted into fuse, and BMS interrupted before fuse blew. Which doesn't prove fuse is good for case of failed BMS. Need the right test setup.
 
upnorthandpersonal said:
I would not trust fuses from Aliexpress. As most of you know, I don't mind trying (and putting to use) cheap equipment - but I don't skimp on fuses.
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A past friend labeled me the King of Cheap

Then again, my stuff always worked (automotive stuff) and he was a mechanic yet had frequent breakdowns. Whatever.

For my new LiFePo batteries I bought UL Listed Class T fuses. You can skimp, compromise, or finagle some things. But like with heart bypass surgery, do you want to go to a hospital? Or an unmarked door off a cluttered alley in a big city to get it done?
When life and death are at stake, don’t fly Lo-buck Airways
 
Unless I purchased fake Bussman fuses, I dont see what the difference is where I bought them. If you are getting fuses from some trusted supplier that has personal relationships all the way up the supply chain to the factory in india then go for it, but just because it comes from aliexpress doesn't mean it's fake. The fuses I received have thick tin plated copper tabs and measure the same dimensions as the datasheet with my calipers. I have no reason to suspect they aren't authentic. In my experience counterfeit electronics usually skimp on metal thickness or materials.

Also, blue sea systems doesn't even make those class T fuses that you can buy on amazon shipped from some random marine supply company. They don't even post a datasheet. How much do you trust that supply chain? My point is there's always a risk. There's a lot of other things that people buy from china that can catch on fire too: like an MPPT controller, inverter, or BMS. Just because paying a lot for a fuse makes you feel safer, it doesn't necessarily mean you are safer. But maybe feeling safe is what we're really after.
 
Picked up a 175 amp Blue Seas Class T fuse at Home Depot. Best price I could find. Other size Class T fuses also available at Home Depot.

www.homedepot.com

Blue Sea Systems Fuse A3T (Class T) 175 Amp 5115 - The Home Depot

Fast short circuit response makes this the best choice to protect high amperage electronics equipment such as inverters. 20,000 Amp Interrupt Capacity (AIC) UL rated for DC applications under UL189L. Product quality is managed in a manner consistent with international standards. Quality products...
www.homedepot.com
 
eemarty said:
Unless I purchased fake Bussman fuses, I dont see what the difference is where I bought them. If you are getting fuses from some trusted supplier that has personal relationships all the way up the supply chain to the factory in india then go for it, but just because it comes from aliexpress doesn't mean it's fake.
Click to expand...

Risk management and consistency. There are tons of fake circuit breakers on Aliexpress, there was a huge issue with fake Bussman fuses, etc. There are also tons of bad LiFePO4 cells on Aliexpress for example. In addition, a lot of "store 12345" sellers that never ship. Now, I buy stuff on Aliexpress (and Alibaba - I have a platinum account there) - all the time. For most equipment, I don't mind. But the thing that is to protect the set-up when that equipment goes wrong, I want to make sure it works properly and according to spec. I trust Mouser, Farnell and Digikey supply chains much more than a random Aliexpress seller.
 
A.Justice said:
A 280 amp hour cell at 20c is 5600 amps. A 2p version of that (which a lot of people have, and more) is almost 12k amps, which is higher than most MRBF or ANL fuses can handle. If you have a large bank, you could potentially short with tens of thousands of amps.
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What if you put an MRBF on the terminal of each battery in the bank (assuming the bank doesn't contain too many parallel batteries)?
 
filippomasoni said:
Those are very interesting and useful in some applications, but I'm afraid they are too slow and with a braking capacity at only 5000amp @ 32vdc not enough for lifepo4
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Could you please share your calculations of max short circuit current of and LFP battery or reference a manufacturer datasheet that provides the value? Thanks.
 
RotEvery said:
Could you please share your calculations of max short circuit current of and LFP battery or reference a manufacturer datasheet that provides the value? Thanks.
Click to expand...
With certain failures that the fuse is the safety should “an event” occur the discharge could be 20,000A, or 10kA, or whatever if BMS mosfets or something fail closed. The Class T is designed to successfully open that circuit without internal bridging, and iirc Class T contains an arc extinguishing powder. Lead Acid shorted discharge is less instant current so a ‘lesser’ rated fuse is required, but lithium loves to release current like some dogs love to chase a ball. Just won’t quit until energy is exhausted.
 
RotEvery said:
Could you please share your calculations of max short circuit current of and LFP battery or reference a manufacturer datasheet that provides the value? Thanks.
Click to expand...
I've shorted a single 25 ah LiFePO4 cell and it maxed out my meter at 200a. I also used a 4s pack of the same 25ah cells to start my cold V8 that takes over 500a to crank, it coughed a bit, but did crank, leading me to believe that the maximum pulse discharge rating is around 20c for those cells. I don't see any reason to believe that other LiFePO4 cells perform that much differently.
 
My math is as follows - a 3.2V cell with IR of 0.25mOhm and busbar with a resistance of 0.15mOhm (including terminal to busbar resistance) can produce no more than 3.2V / 0.40mOhm = 8kA. It doesn't matter how much you put in series - the current can not go over 8kA with these numbers.

And this is the theoretical maximum. The IR will likely spike under such load and the current will not get to 8kA. But still - I do recommend 20kA fuse. Why - because better safe than sorry.
 
MarvRVHam said:
I'm about to start my upgrade to our RV electrical system. It will be a Victron MultiPlus 3000 with 4 Battleborn Batteries and 700 watts of solar. I went and go everything from BattleBorn but noticed that they supplied me with a 400 Amp ANL fuse to place between the battery and the inverter (it would have been nice if they supplied the fuse holder as well). Prior research that I've done indicates that a 400 Amp Class T fuse would be a better choice. But since I'm sure that the people at BattleBorn know more than I do should I just go with the ANL type, or replace it with a Class T? The cost difference doesn't matter to me. My primary concern is keeping my RV electrical system and everyone in the RV as safe as possible at all times.. Thoughts?
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Hold one of each complete fuse / block in a different hand , feel it..look at it …then you decide…
it will be an easy choice…
Class T for all my important fuses except in the small 12/24 accessory distribution blocks …but that’s probably just me…don’t get hung up on that theory…
blue sea Class T fuse block # 5007 for 110 - 200A ..#5502 for 225A to 400… they are not interchangeable. Different gap length and size posts. All have a real cover that works , 5007 has better latching cover.
( HINT) Having a bunch of BB and the same inverter you have , you may want to discuss the fuse amp ratings needed with Battle Borne tech guys depending on how you wire your batts for voltage and the size wire your using and how you configure things…I was surprised when I did…but we have totally different systems lay out …...it would have saved me a lot of money if I had known earlier… jus sayin..

blue seas sell fuses for them from 3 manufacturers .. some are fast ,some are not…all are good… oddly , prices are lower and more available for the 5502. I have seen some cheap knock off ClassT fuses ( they say) recently online..if it’s real cheap be wary.. real wary….

All have been scarce untill the recent months.. still not cheap as once was ..but at least you sorta can get them for about a hundred- ish, +/- ,complete . The 5007 are a bit more with the fuse…. The 110 fuse has been the hardest to find it seems. The holders I have are rated for 125V To 160 V.

You may have to dig a bit to find what you want .
during the virus fiasco thing ,you really had to dig…
everything I just said may change at any point ….so who knows…
 
brum said:
My math is as follows - a 3.2V cell with IR of 0.25mOhm and busbar with a resistance of 0.15mOhm (including terminal to busbar resistance) can produce no more than 3.2V / 0.40mOhm = 8kA. It doesn't matter how much you put in series - the current can not go over 8kA with these numbers.

And this is the theoretical maximum. The IR will likely spike under such load and the current will not get to 8kA. But still - I do recommend 20kA fuse. Why - because better safe than sorry.
Click to expand...

Until you start putting cells/batteries in parallel...
 
brum said:
My math is as follows - a 3.2V cell with IR of 0.25mOhm and busbar with a resistance of 0.15mOhm (including terminal to busbar resistance) can produce no more than 3.2V / 0.40mOhm = 8kA. It doesn't matter how much you put in series - the current can not go over 8kA with these numbers.

And this is the theoretical maximum. The IR will likely spike under such load and the current will not get to 8kA. But still - I do recommend 20kA fuse. Why - because better safe than sorry.
Click to expand...
Just the kind of result I expected. In reality it would be less than this. Which is why the Blue Sea terminal fuses should be okay for a 12V system. They are closest to each battery and have enough AIC rating. Going for the Blue Sea class T fuses seems not technically required (which means the extra cost is not necessary) but good for those wanting to be extra cautious. For others it seems like overkill for a 12V system.

With all the technical capacity Victron's has, Victron still recommends (and sells) Mega / CNN/ ANL fuses which have lower AIC rating than the Blue Sea class T fuses for this same type of service.....
 

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filippomasoni said:
Those are very interesting and useful in some applications, but I'm afraid they are too slow and with a braking capacity at only 5000amp @ 32vdc not enough for lifepo4
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I see your point. For 24V and 48V systems maybe one should go for the class T fuses. Are the Blue Sea terminal fuses slower than the MEGA/CNN/ANL fuses that Victron recommends?
 
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