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diy solar

MIDI-based alternative to MRBF or ANL with higher AIC


New Member
Oct 23, 2023
Downeast Maine
Just sharing this fuse option for those with smaller systems considering MRBF or ANL:

Littelfuse MIDI High Performance 70V

(Available at waytekwire, mouser, digikey and other places for about $4).

It has 2,500 AIC @ 70V (Spec sheet doesn't list lower voltages, but if it functions like all the other fuses, that should mean at least 5,000 @ 32V and at least 10,000 AIC at 14V). Available 30A-200A. Same form factor as other MIDI fuses. Spec sheet says 1Megaohm of resistance in open state up to 70V (which works out to far more AIC, so I must be missing something in how that factors in).

For comparison, MRBF is only 2,000 AIC @ 58V [BlueSea spec sheet], so in theory, this fuse should perform substantially better than the oft recommended MRBF (though I have no idea why people recommend it as a better AIC option over ANL which has higher AIC when you compare them at their only comparable spec of 32V).

Anyhow, the midi factor makes it cheap, small, and a nice perk is that it can be fit into fuse-block bus-bar combo such as these:

Available at waytekwire and elsewhere...

Just sharing because I've been researching for a couple days and was very happy to find such an elegant and affordable option. The nice thing about these Eaton MIDI fuse blocks is that they interlock and can be combined. (The product series is LMI, and it's only a few bucks for each fuse block and another few bucks for the bus bar).

(My plan is to bring the battery positive in from one side through it's main fuse into the busbar, and then distribute to the inverter/scc/lvd from there with the same style MIDI fuses, eliminates a lot of wires and connections).

If you prefer to have a real cadillac of a bus bar fuse block, this one takes MIDI (and a single MEGA) and is from an actual cadillac:|tkp:Bk9SR4ac58eJYw


But the cadiallac, while a bit cheaper all said and done, is topless...
@740GLE - Fortunately all these products have spec sheets. Simply look up your chosen MEGA fuse and compare AIC. Most MEGA fuses I've seen are 2,000A @ 32V. So yes, these should be much better since they are 2,500A @ 70V (which is absolutely better, but, in theory, it should come out to at least 5kiac at 32V to the best of my knowledge).

@yabert - wow, excellent thread you have there. It's strange to me that there keeps being this common-knowledge that you should always use Class-T fuses. The one research paper that's out there has 12C short circuit current on tested 160Ah and 8Ah cells. There are breakers that do 10kaic @ 120V, there are several of fuses out there as you found that have impressive AIC at high volts. Plus, all the high end LiFePO4 manufacturers like BattleBorn and Dakota are using ANL or MRBF fuses... for most setups there are a lot of nice fuse options and Class T appears to me to have no benefit over these other options.
Class T appears to me to have no benefit over these other options.
I can see some advantage like blowing time at XXXX amps at 0.001 sec instead of 0.01 sec. Maybe that can save some electronic.
But this is only true if you have a big and powerful battery able to output XXXX amps in 0.001 sec during short circuit event.
It's clear to me than most ''small'' 5-10 kWh battery don't have huge benefit to have class T.
Also, all this is only true for high quality/high price class T fuse and many affordable class T fuse are not better than some new low cost alternative like AMH, AMX and HP70V fuses.
Looking closely at spec sheets just before ordering, I think your AMX find is better than the Littelfuse MIDI Hi Performance because it actually followed standard AMI/MIDI size -- it looks like the Hi Performance one has the holes spaced at 36mm instead of 30mm. The AMX one is 30mm (like all the other MIDI/AMI). Strange why Littelfuse would make it 6mm larger.

At DigiKey the AMX is $7.50 and the MIDI Hi Performance is $4.50. Definitely worth $3 to have it fit standard midi fuse holders (can't find which fuse holder the MIDI HP would fit in -- confusing they'd call it MIDI but not keep the footprint the same).

I also agree, I'd much prefer to get a UL Listed Eaton or Littelfuse that may be slightly less AIC than a Class T, than to buy an unknown import class T.
This 6mm extra seems to be a thing with Littelfuse. They have a MEGA High Performance series too (as much as 2500 @ 120V!). They say in the catalogue that they are 6mm wider so that they aren't accidentally replaced with one of the standard fuses by a user (say, in an automotive application). Unfortunately, they don't address how MEGA HP or MIDI HP fuses wont work in their fuseholders.

Whereas, the Eaton AMX actually follows Eaton AMI hole spacing.