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  • Breakers vs Fuses

    Can you run DC though circuit breakers instead of fuses....like between my 40amp controller and my batteries....like maybe a 40amp breaker.... Good idea or not good. Tks

  • #2
    Yes as long as the circuit breaker is rated for DC voltage. Some of the cheaper ones will not handle DC being open under load and arc.

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    • #3
      Most fuse holders may state "Touch Safe" so you don't get shocked, but most are not rated to be opened up when the circuit in energized. The fuse holder itself will arc and ruin it's contacts, as it relies on the fuse part to safely break the circuit.

      DC rated breakers can be rated Switch Duty like the series MidnightSolar carries and you can switch things on and off, compare PV string A to B to C and quickly find a dud. And disconnect the PV when you need to reboot the Charge Controller. There is a higher investment going with CB's instead of fuses, but the convenience factor is so much higher.

      Midnight DC breakers
      http://www.midnitesolar.com/productP...Order=18&act=p
      mounting box
      http://www.midnitesolar.com/productP...tOrder=1&act=p
      Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
      || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
      || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

      solar: http://tinyurl.com/LMR-Solar
      gen: http://tinyurl.com/LMR-Lister

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      • #4
        For the Battery, ANL or Class T fuse is the way to go.

        Between the controller and a battery may not be a good idea for circuit breakers. Has to do with an AIC rating of the circuit breaker. Same thing with fuses. With a battery being able to push a lot of power, the circuit breaker or fuse could blow, and then the there’s still enough power to arc across the gap. I think AIC stands for Amps interrupted Current.

        I have lead acid batteries and an ANL fuse is fine, but I’m upgrading to Lithium Batteries and I will add a class T fuse. I did not find a Circuit Brekaer that could handle the amount of amps that could be delivered if the circuit breaker tripped. Other fuses like an ATC fuse or Maxi fuse could not handle the amount of amps that could be delivered when tripped without arcing across.

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        • #5
          Originally posted by chrisski View Post
          ........upgrading to Lithium Batteries and I will add a class T fuse. I did not find a Circuit Brekaer that could handle the amount of amps that could be delivered if the circuit breaker tripped.........
          But isn't the BMS for the Li battery supposed to limit the current to protect the battery ?

          Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
          || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
          || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

          solar: http://tinyurl.com/LMR-Solar
          gen: http://tinyurl.com/LMR-Lister

          Comment


          • #6
            Yes the BMS provides current protection but the MOSFETS can fail in the shorted position. BMS is supposed to be a last resort.

            There is a few videos of batteries shirting out and it’s the class c fuse that blew and not the BMS protection for over current.

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            • #7
              So... i'm installing a epever 40amp solar controller....would a 40amp fuse between the controller and the batteries be the right size fuse ???









              ///

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              • #8
                Would need to be bigger than 40 amps. That prevents nuisance tripping

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                • #9
                  ok chris tks....50 .....60 ????

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                  • #10
                    I'd use something in the 50A ballpark. And use 50A rated wire. You really don't want it to open, because a charge controller with PV active and no battery, gets overvoltaged and dies soon. It's really only there for safety if the controller fries itself and tries to short the battery. Then you want something to blow, and you are assuming the controller is already toast.

                    My first TSMPPT-60 fried itself after 2 years, a small PCB inside blew, and that tripped my 60A breaker. With my PV array, all the controller can produce is about 40A, so I knew the PV would never trip it offline - even with cloud edge events
                    Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
                    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
                    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

                    solar: http://tinyurl.com/LMR-Solar
                    gen: http://tinyurl.com/LMR-Lister

                    Comment

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