Fuse and/or Circuit Breaker between Controller and Batteries?

I have installed solar panels on my RV and am in the process of hooking everything up. There is a 15A breaker between the panels and the controller and am now getting ready to connect the controller to the batteries. I purchased both a (100A) fuse (http://bluesea.com/category/5/21/productline/128) and a 60A thermal circuit breaker (http://bluesea.com/category/3/10/productline/docs/174) to use as a battery disconnect. But now I'm wondering why I need to install both? Will the circuit breaker suffice?

And bear with me if this is dumb question, but the circuit breaker's terminals are labeled "load" and "line." It is just not clear to me between the controller and the batteries what is considered "load" as they are both basically harnessing the energy. Could someone please enlighten me on this?

Comments

  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Fuse and/or Circuit Breaker between Controller and Batteries?

    A fuse and a circuit breaker on the same circuit is redundant.

    As for wiring, "LOAD" = out and "LINE" = in. The load for the PV's is the charge controller, but the load for the charge controller are the batteries. The load for the batteries is the inverter.

    Are you sure you've calculated the circuit protection correctly? There's a big difference between 60 Amps and 100 Amps. One of these is the wrong size for your system.
  • iabteriiabteri Solar Expert Posts: 45 ✭✭
    Re: Fuse and/or Circuit Breaker between Controller and Batteries?

    Thanks so much for the response.

    I will just install the circuit breaker. I have the TriStar MPPT 45 Controller and the manual recommends a 56.3 amp minimum. I already had some 100 amp fuses as I installed one of those fuse blocks between the batteries and the inverter, so I was just going to use the same fuse.

    So, just to verify, I connect the "load" terminal to the batteries and the "line" terminal to the controller?
  • CrotalusCrotalus Solar Expert Posts: 26
    Re: Fuse and/or Circuit Breaker between Controller and Batteries?

    You might want to read your manual again. I have a 20amp MPPT controller in my trailer and the manual that came with mine stated; Install a fast acting 30 amp fuse as close to the battery as possible on the positive side. I don't believe you want a self setting circuit breaker in the system. I have a AGU fuse next to the battery with enough wire to remove the battery. The AGU fuses are DC rated at 32v and can be had in a 60amp size. Bussman makes several types of fuse holders for the fuses or you can get them at any high-end automotive stereo stores as they are a common component for amplifiers.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Fuse and/or Circuit Breaker between Controller and Batteries?

    45 Amps * 1.25 = 56.25 = 60 Amp circuit protection. Nothing wrong with using a DC rated breaker such as the one you link to. Using the 100 Amp fuse as well would be a waste, as the breaker would trip first. It should be located as close to the current source as possible - in this case the charge controller.

    And yes the "load" in this application is the batteries.
  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Fuse and/or Circuit Breaker between Controller and Batteries?

    think in terms of flow as source and load as it is source to load. for example it isn't coming from the controller to the pvs by flow as it is from pvs to the controller. pvs = source and controller = load. furthering this we find with the controller and the batteries that it flows from the controller to the batteries making the controller the source and the batteries the load. one could surmise if you have both that the pvs are the source and the batteries are the load, but it is a point of view.
  • iabteriiabteri Solar Expert Posts: 45 ✭✭
    Re: Fuse and/or Circuit Breaker between Controller and Batteries?

    Great info regarding load. I could not find this info anywhere on the web.

    I have the circuit breaker installed and the batteries connected. I installed the breaker in the battery compartment which is in one of the "basement" storage compartments of the RV. The cable is about 8 ft from the batteries to the controller so, hopefully, this will be okay. I'm using #2 cable rather than the recommended #10 because the guys that installed the batteries used #2.

    Okay, so now I am getting ready to wire the controller from the batteries and the array and I have one more question before I do this.

    I checked the volts coming out of the array and I'm getting a reading of –56 instead of a positive number. Is this right? The number is about right but why is it negative?
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Fuse and/or Circuit Breaker between Controller and Batteries?
    iabteri wrote: »
    Great info regarding load. I could not find this info anywhere on the web.

    I have the circuit breaker installed and the batteries connected. I installed the breaker in the battery compartment which is in one of the "basement" storage compartments of the RV. The cable is about 8 ft from the batteries to the controller so, hopefully, this will be okay. I'm using #2 cable rather than the recommended #10 because the guys that installed the batteries used #2.

    Yes: always use the largest wire that will fit (and you can afford); it's a sure-fire way to make certain the fuse/breaker is the 'weakest link' as it should be.
    Okay, so now I am getting ready to wire the controller from the batteries and the array and I have one more question before I do this.

    I checked the volts coming out of the array and I'm getting a reading of –56 instead of a positive number. Is this right? The number is about right but why is it negative?

    Two possibilities I can think of:
    1). you hooked the Voltmeter up backwards.
    2). the panels have the word "Sun" in their name and are that brand that are positive ground (which I can never remember which it is).

    If it's #2, you could have a problem as the rest of the system is probably negative grounded to the chassis.
  • iabteriiabteri Solar Expert Posts: 45 ✭✭
    Re: Fuse and/or Circuit Breaker between Controller and Batteries?

    I have three Kyocera 135 watt panels.

    I'm taking the voltmeter reading the same way I'm taking it for the batteries. V DC at 20 for the batteries, V DC at 200 for the panels. The batteries are a positive number.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Fuse and/or Circuit Breaker between Controller and Batteries?

    You've just got the polarity reversed when checking the panels. Try it the other way 'round. It's very important to hook (+) to (+) and (-) to (-) when connecting panels to charge controller.
  • iabteriiabteri Solar Expert Posts: 45 ✭✭
    Re: Fuse and/or Circuit Breaker between Controller and Batteries?

    Geesh, I do have the polarity reversed! Hard to believe because I was very careful hooking this up. So this brings me to another question:

    When I brought in the solar wires, I had to add extensions to bring into the RV, so I assumed that the extensions created reverse polarity on the panels. That adding an extension to the positive cable out of the panel now created a negative cable. Something tells me this isn't the case.

    If so, then I have the negative wire connected to the circuit breaker between the array and the controller!
  • iabteriiabteri Solar Expert Posts: 45 ✭✭
    Re: Fuse and/or Circuit Breaker between Controller and Batteries?

    If I do have the wires reversed at the breaker, then (with the breaker off) do I just disconnect the panels, then reverse the wires in the breaker box before reconnecting the panels?

    This is all very new to me, and I have a major learning curve going on here, which is why I prefer to fully understand before proceeding.

    Thanks again for your help.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Fuse and/or Circuit Breaker between Controller and Batteries?

    Technically it doesn't matter if you switch and/or fuse either the positive or the negative in an isolated DC circuit.
    But there's that tricky word; isolated. At some point it may not be, and so even though you switch off the (-) at one location there could be an alternate route for it so power could still flow. An example of this is that most charge controllers run the negative 'straight through' as it were and act on the positive side. If the (-) is grounded to chassis in the 'right' two locations, switching off the (-) side may not actually disconnect anything!

    How did you make these extensions for the PV wires?
    I'd suggest you unhook it all, then carefully connect first the negative all the way through, then the positive with appropriate fuses/breakers/switches as needed.
  • iabteriiabteri Solar Expert Posts: 45 ✭✭
    Re: Fuse and/or Circuit Breaker between Controller and Batteries?

    The panels came prewired with those Multi-Contact locking connectors, so I purchased an extension to add to the first and last panel to pull into the RV.

    I actually have the panels hooked up correctly. However, after I added the positive connector to the negative connector coming off the panel, I assumed that connection was now positive, but it was actually still negative at the other end, so I basically had the wires reversed in the breaker and then (almost!) into the controller. Now that I think about it--well, I don't know what I was thinking!

    I was confused at this early juncture and should have had that clarified. Once again, a lesson learned the hard way!

    Luckily, I'm pretty paranoid with this whole install and stopped and asked before hooking up the controller.

    Today I also learned what a negative number means on the voltmeter!

    I'll try this again.
  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Fuse and/or Circuit Breaker between Controller and Batteries?

    when you have dc electricity of either polarity flowing through a wire, it does not matter what connector or even color of wire you put to that same original wire as its original polarity will be the same. the proof is what your voltmeter showed.
  • iabteriiabteri Solar Expert Posts: 45 ✭✭
    Re: Fuse and/or Circuit Breaker between Controller and Batteries?

    Thank you, Cariboocoot, for walking me through this project and Niel for your additional input.

    I had everything wired by dusk Sunday night, and the system has been up and running since then. Very cool!

    I've learned alot on this forum and am grateful it is here.

    Thanks again.
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