AIC Ratings for LiFePO4 - Class T - MRBF

Q&A and troubleshooting
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41

Related question and if anyone can comment I would certainly appreciate it.

Is there any advantage to having a T-Class fuse in the battery that can break 50kA and then also a Megafuse in series in the Lynx distribution? Reason I am asking is we have a Lynx M10 distribution that we want to connect two new 48V LiFePo batteries to.

The batteries have fuses in them with a rated working voltage: DC110V; Rated current: 300A; and a Breaking ability: DC50kA, time constant<11ms;
Performance reference IEC60269, reliability in accordance with ISO 8820, JASO D622, GB/T 31465.

I assume this fuse will do the important AIC work, but as there is also place for a Megafuse in the Distribution, would it be helpful to also have a Megafuse for regular voltage overprotection before the AIC rated fuses?

I have read that it is good practice to install main fuses within 7 inches of the battery’s positive terminal and add secondary fuses at charge controller inputs, inverter outputs, and parallel battery connection points.

Many thanks for any comments or hints..

42

If I understand what you are proposing currently. You are asking if having multiple fuses in series has any value?

Maybe one would pop before the expensive mrbf/class-t ?

Not a great reason though.

Why not just pick up from the bus on the distributor and use it fuseless? (Fused at the battery anyway)

I would personally not trust any battery manufacturer from China and run my own extra fuses just for peace of mind.

There might be some fringe case for series fuses but I’m not aware of it.

Do you know any more about the battery fuse?

43

Yes, within reason. Be aware this might strain the battery posts. Be thoughtful.

Secondaries sound reasonable on both the input AND output of mppt. Maybe this is overkill

Come to think of it, I don’t really know the philosophy of fusing both sides and I’d like some clarification too.

Initial thought is just inputs but I’m not sure.

44

Might entirely depend on where you’re feeding to, and that devices current limits

45

Thanks for reply, appreciated!

I am thinking something similar to you, that I want redundancy for the fuses in the batteries.
Possibly 250A Adler EF3 fuses that states it can handle 50kA also.
I don’t know anything more about the existing fuses in the battery cases than what I wrote in my first post. But the AIC of 50kA seems appropriate?

You write you want safety for the Chinese fuses, so an Adler EF3 in the Lynx Dist series after the one in the battery could be appropriate too?
Or am I misunderstanding you? Thanks.

46

I’m currently drinking so I’ll re-asses in the morning but if you want redundancy by all means put another fuse in series. Just not sure what it offers or rather what you want out of a secondary fuse. I will stay out of it until someone more versed chimes in the we can learn from

47

The obvious answer to that would be what you said: that one might not trust the cheaper fuse in the battery.
Another obvious alternative to that is to upgrade the fuse in the battery to something more trustworthy.
Or do both if there are no drawbacks.

48

FWIW. Had to make a decision so started by replacing the fuse in the battery with a good quality Class T fuse. Seemed like a good place to start,
Looking at also replacing the mega fuses at the battery connection points in the Lynx with Adler EF3 if research confirms it soon.