Circuit breaker setup

simmtronsimmtron Solar Expert Posts: 87 ✭✭✭
I'm just curious about setup of circuit breaker between charge controller and batteries. I have a breaker from Auto zone and one terminal says Bat and one says Load. Now normally I would think the charge controller should be thought of as Battery and the batteries as Load as that is the way the current is going. BUT, I was thinking the circuit breaker would be better protecting charge controller from the batteries if a short came from the batteries. Just wondering best way to hook up as I guess the circuit breaker will trip one way better than the other. Or maybe it doesn't matter? Any opinions?


  • BB.BB. Super Moderators, Administrators Posts: 32,609 admin
    edited April 2017 #2
    Your second thoughts are correct. The circuit breaker is protecting the wiring from the current provided by the battery bank. (solar panels, the circuit breaker protects the "shorted panel" against the other parallel panel strings).

    There can be an issue with many DC circuit breakers... They are designed to stop the short circuit current in one direction only. They can have a permanent magnet near the contacts. The magnetic field will "blow the arc" away from the contacts and into the arc channel/quenching channel. If the current flow is "reversed", the magnet can pull the arc into the mechanics of the breaker.

    Newer breaker standards are requiring DC breakers to work correctly regardless of the direction of the current flow.

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • simmtronsimmtron Solar Expert Posts: 87 ✭✭✭
    edited April 2017 #3
    I have the batteries fused that go to a bus bar and from the controller to the bus bar the circuit breaker.
  • EstragonEstragon Registered Users Posts: 4,496 ✭✭✭✭✭
    I suppose you could get away without the breaker then, but the breaker are handier to depower when need be.
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
  • simmtronsimmtron Solar Expert Posts: 87 ✭✭✭
    Yes I really use the circuit breaker mostly for shutting power to the charge controller.
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