High power fuse question... too many?

[Zybane]

I'm building an overland rig and using this example diagram:




There is a 400 Amp T-class fuse between positive battery and cut off switch. But there is also a 400 Amp T-class fuse coming off the positive bus bar on the cable headed to the Inverter/Charger.

My question is.. if any short happened on that leg between positive bus bar and Inverter/charger, wouldn't the fuse between positive terminal battery and cut off switch take care of it? All the other items on the positive bus bar are behind circuit breakers.

If the fuse between Inverter/Charger and positive bus bar is required, wouldn't it be better to place it at the output of the Inverter/Charger (power going from Charger TO battery) and not close to the positive bus bar?

Just curious if that extra $100 fuse holder and T-class fuse between Inverter/Charger and positive bus bar is really doing anything.

 

[rodrick]

Class t fuses are great but not required for 12 volt systems you could use a Anl or mrbf type fuse and fuse each battery individually for better protection and use a larger main fuse for the inverter main feed for the same cost or maybe even less
When dealing with Lifepo batteries a fuse or breaker on each battery is a must imo

 

[mikefitz]

Just curious if that extra $100 fuse holder and T-class fuse between Inverter/Charger and positive bus bar is really doing anything

Since that path is already protected by the main fuse, the second fuse is not really required.

a Anl or mrbn type fuse

Depending on manufacturer ANL may only have 2000 amps withstand, MRBF have 10000 amps withstand in a 12v system

 

[Zybane]

Class t fuses are great but not required for 12 volt systems you could use a Anl or mrbf type fuse and fuse each battery individually for better protection and use a larger main fuse for the inverter main feed for the same cost or maybe even less
When dealing with Lifepo batteries a fuse or breaker on each battery is a must imo

Since that path is already protected by the main fuse, the second fuse is not really required.


Depending on manufacturer ANL may only have 2000 amps withstand, MRBF have 10000 amps withstand in a 12v system

I have a single 6 kWh Lithium so it has tons of juice that it could throw out all at once, just to be safe I went with T-class.

That was my thought with the single T-Class between the battery positive terminal and the disconnect switch before the positive bus bar. If any of that large cable between battery positive, positive bus bar and inverter were to short to ground, the in-rush current from the battery is going to instantly overwhelm any other power source and blow the fuse.

And if the wire between the charger/inverter and positive bus bar were to short to ground, the inverter is going to shut down way before it blows a 400 amp fuse I would imagine.

 

[rodrick]

Going with a class t fuse is by far the best
One question is when you add more batteries are each going to be fused if so you may what to size the fuse closer to the bms capacity I went with 1.5 times the bms rating

 

[scrubjaysnest]

I used MRBF fuses. 125 amp for each battery to busbar and 300 amp from busbar to inverter.