Fuse size for battery

navillus

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Using a 200Ah lithium battery. I am looking for fuse sizing for the bolt on battery fuse. Maximum load on the system is 120 amps with everything switched on. Should I use a 150amp fuse or a larger fuse like a 200amp? Any information is much appreciated. Also wire size chart shows 120 amps I should use 2awg wire from battery to busbar, does this sound correct.

Thanks
 
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Using a 200Ah lithium battery. I am looking for fuse sizing for the bolt on battery fuse. Maximum load on the system is 120 amps with everything switched on. Should I use a 150amp fuse or a larger fuse like a 200amp? Any information is much appreciated. Also wire size chart shows 120 amps I should use 2awg wire from battery to busbar, does this sound correct.

Thanks
Fuse headroom is determined by dividing service current by .8
120 service amps / .8 fuse headroom = 150 fault amps

150 fault amps is right a the limit for pure copper 4 awg wire with 105c insulation.
I would go with 2 awg.

The entire path between the 120 amp load and the battery needs to be 2 awg or better.
How did you determine your max load was 120 amps?
 

navillus

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Fuse headroom is determined by dividing service current by .8
120 service amps / .8 fuse headroom = 150 fault amps

150 fault amps is right a the limit for pure copper 4 awg wire with 105c insulation.
I would go with 2 awg.

The entire path between the 120 amp load and the battery needs to be 2 awg or better.
How did you determine your max load was 120 amps?
100 amps inverter draw, 20 amps Dc fuse block.
 
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100 amps inverter draw, 20 amps Dc fuse block.
Did you remember the conversion efficiency of the inverter?

For an inverter the common method is
inverter continuous watts / .85 conversion factor / low cutoff voltage = inverter service amps

The dc fuse block is probably rated for 100 amps so I would use 6 awg wire and a 100 amp fuse between the busbars and the dc fuse block.
But the wires between the battery and the wire block should be 2 awg with a 200 amp fuse.
The wires between the busbars and the inverter should also be 2 awg but with a 150 amp fuse.
The reason for using a slightly smaller fuse on the inverter branch circuit is so that a fault on the branch will have a better chance of being isolated to the inverter branch circuit leaving the battery and the rest of the branches operational.
 

navillus

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Did you remember the conversion efficiency of the inverter?

For an inverter the common method is
inverter continuous watts / .85 conversion factor / low cutoff voltage = inverter service amps

The dc fuse block is probably rated for 100 amps so I would use 6 awg wire and a 100 amp fuse between the busbars and the dc fuse block.
But the wires between the battery and the wire block should be 2 awg with a 200 amp fuse.
The wires between the busbars and the inverter should also be 2 awg but with a 150 amp fuse.
The reason for using a slightly smaller fuse on the inverter branch circuit is so that a fault on the branch will have a better chance of being isolated to the inverter branch circuit leaving the battery and the rest of the branches operational.
Thank you for the information. Inverter runs about 83 amps, 100 amps factors in efficiency. How do you figure 2awg wire from fuse block to Busbars? I have under 20amps of draw of The fuse block. Thanks
 
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Thank you for the information. Inverter runs about 83 amps, 100 amps factors in efficiency. How do you figure 2awg wire from fuse block to Busbars? I have under 20amps of draw of The fuse block. Thanks
I didn't, its 6 awg from busbars to fuse block.
I would provision the feeder ciruit for the backplane capacity of the dc fuse block.
That way if you need to add more circuits you are not hamstrung.
 

navillus

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I didn't, its 6 awg from busbars to fuse block.
I would provision the feeder ciruit for the backplane capacity of the dc fuse block.
That way if you need to add more circuits you are not hamstrung.
6awg is what I meant, typo. Ok, understand your rationale. Thanks
 

WYtreasure

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A Class-T Fuse seems to be the best, as far as I know, fuse to put as close as practical to the battery.
I also have a 200 Ah battery and the fuse linked below.

If you get the same product as I the lugs will be 3/8". I have no torque info for you though.
 

navillus

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A Class-T Fuse seems to be the best, as far as I know, fuse to put as close as practical to the battery.
I also have a 200 Ah battery and the fuse linked below.

If you get the same product as I the lugs will be 3/8". I have no torque info for you though.
Awesome! Thanks.
 
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