Two batteries (LFP). Diagonal vs. busbar method considerations

[SteveK]

I have exhausted my search for any other class T fuse to match the Mersen 50kA @ 160V and could not find any. I did find a forum a post at Panabo by a reviewer of the Epoch 460 who posted the data sheet and said that Mersen has their own test facility. That was also the only such confirmation.
Mersen mostly make VAC fuses but tested their A3T themselves at 50kA @ 160VDC and provided a higher rated fuse than all the others available for our needs are 20kA @ 125. Maybe others will follow, but this is great news for those with more than a 400Ah battery bank.

 

[luna]

Luna we agree on the bolded ABYC. Then, the reduction of voltage allows the AIC goes up. Do we agree on that?

Good to see that almost neighbours, agree on the basics.

I would expect that typically the ability of a fuse to quench an arc goes up with a reduction in voltage.

Maybe that could be calculated, but I would expect it would take years of research before any of the authorities having jurisdiction would accept a calculation. In the meantime I think we use testing.

 

[DDW]

In any case, I don't think UL would accept a calculated value without a tremendous amount of research to back it up. It is pretty simple to test, but there has to be a motivation to do it. Then you have to go through the paperwork to gain UL certification. The lower the voltage, the easier to interrupt the arc - but arcs are odd things, and there is no reason to believe it is all a linear system.

Absent the ABYC E-11 recommendations, I'd have used a 20K AIC@125V fuse in my boat (that is what is in there now feeding the inverter) and felt perfectly protected. I think I am still perfectly protected, just not from the hazards of the ABYC, surveyors, and insurance companies.

 

[Marco Flamingo]

I paid $26 for DC MCCB breakers with 35k Ics and 50k Icu, one for each bank. Basically $50 for 50k AIC for each 560Ah bank. ABYC standards only requires 28k AIC. "Way too much" for my batteries. And the breaker ratings are at 250 DC volts. So at 12V DC, the AIC would typically be higher, i.e., "way, way too much." Nothing wrong with way too much protection unless it is too expensive and complex (i.e., cobbling together Class T as per the above thread).

 

[DDW]

Only problem is, you need a big boat to fit those bulky things.