Choosing a T class fuse for DIY battery

[Robin Hillier]

I am building some 12 volt batteries using 4, 280 ahr cells and a JK-B2A8S20P BMS having a 200 amp continuous current and 350 amp max current rating. I'm placing a class T fuse inside each battery for short circuit protection. This is not the fuse for the complete battery bank, just each battery. Would a 350 amp fuse be appropriate or should I go up to 400? Opinion anyone?

 

[sunshine_eggo]

Fuses are selected based on the wiring they are protecting - 1.25X the wire rating, rounded up.

 

[Robin Hillier]

Fuses are selected based on the wiring they are protecting - 1.25X the wire rating, rounded up.

Thanks. My wiring/busbars will be over-rated, so might it be safer to keep the battery fuse down closer to the BMS specs?

 

[sunshine_eggo]

Thanks. My wiring/busbars will be over-rated, so might it be safer to keep the battery fuse down closer to the BMS specs?

So, the wiring/bus bars you have selected is rated for > 280A?

 

[googdot]

Fuses are selected based on the wiring they are protecting - 1.25X the wire rating, rounded up.

Quick question if you don't mind...I have a breaker between my inverter and battery. When I change from AGM to Lifepo4, are you saying an additional fuse 1.25x my battery link size is also required?

 

[sunshine_eggo]

Quick question if you don't mind...I have a breaker between my inverter and battery. When I change from AGM to Lifepo4, are you saying an additional fuse 1.25x my battery link size is also required?

Unknown. What's the AIC rating of your breaker?

 

[googdot]

Unknown. What's the AIC rating of your breaker?

Breaker is 175A. Inverter is 2kW and is over-spec'd with very light loads.

 

[sunshine_eggo]

Breaker is 175A. Inverter is 2kW and is over-spec'd with very light loads.

What is the AIC rating of the breaker?

 

[googdot]

What is the AIC rating of the breaker?

Sorry I understand now - AIC is 50K at 125VDC

 

[sunshine_eggo]

Sorry I understand now - AIC is 50K at 125VDC

That breaker is adequate for LFP batteries.

 

[Robin Hillier]

So, the wiring/bus bars you have selected is rated for > 280A?

I'm assembling parts to build the batteries at present. Bus bars and cabling will come later.