Fuse for 100 A 48 Vdc line, 40 A 12 Vdc

[flammafeuer]

I'm researching fuses, and seeing different recommendations, and having a hard time sorting it out. I the following lines I think I should fuse:

• Battery bus-->Inverter: 100 A, 48 Vdc
  • Could be 200 A down the road as I have two 48 Vdc batteries in parallel
• Battery bus -->12 Vdc regulator, 40 Adc
• Controller-->Battery bus
  • Should I fuse this?

I looked into the Victron and Renogy fuses, but I see that some people are using much larger and more expensive fuses for their systems (though there might be much higher voltages at play). Any suggestions on fuses for a small off-grid system?

 

[SamDeleted]

All lines to and from bus should be fused

Fuse sizes are based on cable amp capacity and size of the load , there are calculators online but I am happy to go through them with you if needed

 

[flammafeuer]

All lines to and from bus should be fused

Fuse sizes are based on cable amp capacity and size of the load , there are calculators online but I am happy to go through them with you if needed

I could use help on fuse selection beten the Bus bar and inverter. It is 3kW, and can surge up to 6kW. I will be using a demolition hammer that is 1800 W that I could see needing a lot of in rush current. The base fuse for a normal 3kW would be 125A for 48V, but would that allow for surges in current? Also, would I need a slow or fast fuse?

 

[SamDeleted]

Also, would I need a slow or fast fuse?

What kind of batteries do you have please?

 

[SamDeleted]

The base fuse for a normal 3kW would be 125A for 48V, but would that allow for surges in current?

Fuse should be 1.25x~ of the amp draw , I think you don't need to account for the surge current in this case

Your 3kw inverter draws 62.5 amps
3000w ÷ 48v = 62.5amps

62.5 x 1.25 = 78amps~

So am 80amp fuse would be good, or up to maybe100amp if your cable can handle that current . It really depends what you can find

 

[flammafeuer]

What kind of batteries do you have please?

Aolithium rack batteries, 48V 5kW in parallel, though haven't hooked them up yet.

 

[flammafeuer]

Fuse should be 1.25x~ of the amp draw , I think you don't need to account for the surge current in this case

Your 3kw inverter draws 62.5 amps
3000w ÷ 48v = 62.5amps

62.5 x 1.25 = 78amps~

So am 80amp fuse would be good, or up to maybe100amp if your cable can handle that current . It really depends what you can find

How is the 6kW surge taken into account?

 

[SamDeleted]

Aolithium rack batteries, 48V 5kW in parallel, though haven't hooked them up yet.

Lithium batteries have a HUGE short circuit current, they need special fuses

Class T fuse is what people recommend, they cost a fortune

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How is the 6kW surge taken into account?

The surge happens so quickly it's not an issue, fuses aren't usually that sensitive

 

[flammafeuer]

I was also just reading about fuses right after the battery. Is the calculation the same for those, and are T fuses the recommended ones? I see some people using MRBF even on 48.

Edit: you answered this partially above.

 

[SamDeleted]

I was also just reading about fuses right after the battery. It's the calculation the same for those, and are T fuses the recommended ones? I see some people using MRBF even on 48V.

I think when you have 2x 48v lithium batteries in parallel they recommend class-T over mrbf

Calculating the LiFePO4 battery short circuit current

I'm trying to understand how to calculate a LiFePO4 battery short circuit current. I have a 12V 100Ah LiFePO4 battery and the manual states an internal Impedance of 40mΩ. So how to calculate the short circuit current of the battery? Thanks.

diysolarforum.com

This explains a bit

When Is A Fuse Not A Fuse ?

Ensure your off-grid power system is properly protected - use the correct fuse. This article discusses the importance of breaking capacity with fuses or MCBs.

www.solar-wind.co.uk

 

[SamDeleted]

It's the calculation the same for those

I THINK so. I would do further research before buying your very expensive class T fuse.


Hopefully someone more experienced than me will come along and give you a firm answer on that ?