Battery box fuse question

[tammons]

Building a 12v 100 amp Lifepo4 battery box.
I will have the normal USB, cigarette socket, and also a 45 amp Anderson socket (the small ones)
And a 120 amp Anderson. The 120 amp Anderson will be used for an external inverter.
The USB and cigarette sockets will each have their own fuse via a fuse block.
The 45 amp Anderson will have a 50 amp fuse.

The question is about the 120 amp Anderson.
I plan to fuse the main positive battery cable at 250 amps.
Do I also need to fuse the 120 amp Anderson?

 

[12VoltInstalls]

The question is about the 120 amp Anderson.
I plan to fuse the main positive battery cable at 250 amps.
Do I also need to fuse the 120 amp Anderson?

Will your inverter be 120A? (guessing 1200W?)

Why fuse with a fuse that will never blow (250A) if you have “an event?”

 

[tammons]

1200w inverter. Inverter has a peak of 2400w.
But lets say I change to a 150 amp main fuse.
Do I need to also fuse the 120 amp Anderson?

 

[mikefitz]

Do I need to also fuse the 120 amp Anderson?

The connector and I assume its cables are good for 120 thus any battery connected must have a 120 amp fuse in the feed.
Since you cannot pull more than 100 amps from the battery, perhaps put a 120 amp fuse as the main battery fuse.
Fuse the feed to the fuse box.

 

[12VoltInstalls]

1200w inverter. Inverter has a peak of 2400w.
But lets say I change to a 150 amp main fuse.
Do I need to also fuse the 120 amp Anderson

Mikefitz answered the fuse well.

But even the inexpensive units I have confidence recommending (Giandel and QZRELB) have effectively no headroom.

So read this this way: the ‘quality’ inexpensive inverters- lets use 1200W- have usually an advertised “2400W Surge Capacity” but it’s virtually useless as very often that’s in milliseconds.
So I (in my case: you may choose a different opinion) want the 3000W inverter not so I can run ~25A continuously at any time, but rather so that my inductive motor loads at 10-15A running start up more reliably.
“Surge ratings” imho are not usable, but standard label ratings seem to be acceptable.