DC Circuit Breaker

Im running a 48v 200ah battery system and I want to put a 2P Circuit Breaker after the batterys, my Max amp input on my MPPT controller is 48v 71amps. Do I need a 200amp circuit breaker or can I use an 80amp circuit breaker

Thanks!

The breaker should always be sized to protect the cables in the circuit from melting. Per NEC, you generally use the 80% rule which is the max safe current handling of the cable, and the breaker rating should be 80% of that, and cable size has to do with max amps you will ever flow on the circuit, and for longer lengths you must factor in voltage drop into cable size.

Link to example:

EDIT:
The above are general rules for cabling and circuit protection. PV circuit Isc values are generally not high enough to be too concerned about melting cables, still need to be mindful of current potentials, PV circuits usually are sized more for minimizing voltage drops, and circuit protection should still be sized to protect the cable from ever going beyond maximums as a best practice (which are usually beyond what the Isc values are).

wanderinglostadventures said:

Do I need a 200amp circuit breaker or can I use an 80amp circuit breaker

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To add to what @Samsonite said, as long as your wire can handle 80 Amps then an 80 Amps circuit breaker is fine.

Hi @wanderinglostadventures,
Could you share what Circuit Breaker model have you installed? I found it's hard to get a good quality 2P DC Circuit Breaker of that size.

Oleksii B. said:

Hi @wanderinglostadventures,
Could you share what Circuit Breaker model have you installed? I found it's hard to get a good quality 2P DC Circuit Breaker of that size.

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Did you happen to check out the Midnite Solar DC breaker line? I have a bunch of these, and they have sizes to meet a wide range of operating voltages (to guarantee adequate extinguishing of arc during full-current operation)...




More Info:

Samsonite801 said:

Did you happen to check out the Midnite Solar DC breaker line? I have a bunch of these, and they have sizes to meet a wide range of operating voltages (to guarantee adequate extinguishing of arc during full-current operation)...

Category Products - MidNite Solar's

MidNite Solar Category Products.

www.midnitesolar.com

More Info:

Click to expand...

Thanks!

I didn't find the exact specs I need - MCCB DC Circuit Breaker 100A 2 pole.
And ended up with Noark https://www.outbackmarine.com.au/noark-100a-500v-dc-circuit-breaker-2-pole
They're available in Australia only, so a bit challenging to get.

The Noark is available worldwide. Just have to contact them to find out where you can buy them from if it isn't obvious from a web search for your country.