Correct fuse for my setup?

[AZRoadrunner]

I'm trying to size out the correct battery fuse. My build is two Battle Born 12v 100ah batteries in parallel (providing 200ah) and the inverter is a 2kw ExpertPower low frequency inverter/charger, rated at >90% efficiency. The specs for the inverter don't provide a specific surge wattage, but does state the following:

Overload Protection:
110%<load<125%: Shutdown after 15 minutes
125%<load<150%: Shutdown after 60 seconds
Load>150%: Shutdown after 20 seconds

Based on those numbers and functionalities, what would be the correct size fuse at the battery?

Thanks for the assist.

 

[time2roll]

For a 2kW inverter running on 12 volts I would normally recommend a 200 amp Class-T fuse.... however you did not list the wire sizes connecting everything.
Fuse is to protect the wire not the device.

 

[John Frum]

2000 ac watts * 1.5 low frequency fudge / 12 volts low cutoff = 250 dc amps
250 dc amps / .8 fuse headroom = 312.5 fuse amps.
I would put a 150 amp mrbf fuse on each individual battery.

 

[Sanwizard]

2000 ac watts * 1.5 low frequency fudge / 12 volts low cutoff = 250 dc amps
250 dc amps / .8 fuse headroom = 312.5 fuse amps.
I would put a 150 amp mrbf fuse on each individual battery.

I always fuse to just below the capabilities of the cables. You dont want melted cables.?

 

[John Frum]

I always fuse to just below the capabilities of the cables. You dont want melted cables.?

I can agree with that.
Fuses protect wires and appliances protect fuses.
Plus the higher the amperage fuse usually means the lower its resistance.
OP think of my math as a way to find the minimum fuse and wire size.

 

[AZRoadrunner]

Whoops - I didn't mention the wire size. It's 1/0.

 

[John Frum]

Whoops - I didn't mention the wire size. It's 1/0.

You can use up to 285 amp fuse with 1/0 assuming 105C rated insulation.

Interactive Wire Size Calculator

Battery Chargers, Inverters, Solar Components, and Wiring Supplies for Boats, RVs, and Off-Grid Applications.

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[Tdevery]

I have a Magnum 2000 watt inverter. Magnum recommended a 300 amp fuse.

 

[AZRoadrunner]

2000 ac watts * 1.5 low frequency fudge / 12 volts low cutoff = 250 dc amps
250 dc amps / .8 fuse headroom = 312.5 fuse amps.
I would put a 150 amp mrbf fuse on each individual battery.

A related question. I'm considering using bus bars to parallel the two batteries. ONE -- is there a reason not to do that? And TWO -- in that scenario, the two fuses you recommend would go on the positive terminal post for each battery? Thanks.

 

[John Frum]

A related question. I'm considering using bus bars to parallel the two batteries. ONE -- is there a reason not to do that?

Nope busbars is the way to go.
For best results make the battery cables the same length so that they have the same resistance.

And TWO -- in that scenario, the two fuses you recommend would go on the positive terminal post for each battery? Thanks.

Yes.
That is what I was suggesting.
Page 18 of this doco describes the "posts" method.
Its pretty much you are thinking except you will be using busbars.
The key point is to make the path resistance as close to equal as possible/practical.

https://www.victronenergy.com/upload/documents/Wiring-Unlimited-EN.pdf

 

[John Frum]

BTW the inverter/charger is going to need a bigger cable and fuse.
mrbf fuses go up to 300 amps.

 

[AZRoadrunner]

BTW the inverter/charger is going to need a bigger cable and fuse.
mrbf fuses go up to 300 amps.

The wiring guide for the inverter states that the minimum wire gauge for anything less than 1 meter of cable is 60mm2. The closest to that is 70mm2 (2/0 cable). I'll be sure to use 2/0 from the bus bars to the inverter -- and per your suggestion, there should be a third, higher-rated fuse on the connection from the bus bar to the inverter. Correct?

 

[John Frum]

The wiring guide for the inverter states that the minimum wire gauge for anything less than 1 meter of cable is 60mm2. The closest to that is 70mm2 (2/0 cable). I'll be sure to use 2/0 from the bus bars to the inverter -- and per your suggestion, there should be a third, higher-rated fuse on the connection from the bus bar to the inverter. Correct?

Correct.

 

[Jimmynik1]

For a 2kW inverter running on 12 volts I would normally recommend a 200 amp Class-T fuse.... however you did not list the wire sizes connecting everything.
Fuse is to protect the wire not the device.

Picking your brain for a second, 16s 310ah bank feeding a 48v 3.5k hybrid. If the most I can run is 3500w, 30a ac, or 82a dc, what size fuse would you say for my main line fuses. Using #4 wire for the 2' run.
Appreciate it thanks.

 

[time2roll]

Picking your brain for a second, 16s 310ah bank feeding a 48v 3.5k hybrid. If the most I can run is 3500w, 30a ac, or 82a dc, what size fuse would you say for my main line fuses. Using #4 wire for the 2' run.
Appreciate it thanks.

Not sure what the BMS is rated but I would be at 100 to 125 amps not to exceed the BMS rating.

 

[Jimmynik1]

Not sure what the BMS is rated but I would be at 100 to 125 amps not to exceed the BMS rating.

BMS is 100A, going with 4 wire and 100A fuse.
What say you?