fuse from charge controller to batteries

wastwast Registered Users Posts: 41 ✭✭
2x190 watt panels in series with 40 amp mttp charge controller.. 10awg wire from panels to controller> what size wire and fuse do I need to connect to batteries and do I need fuse from panels to charge controller and if so what size.. and is the 10 awg big enough for the panel to controller (about 15 ft is distance from panel to controller and about 5 ft from controller to panel

Comments

  • mike95490mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    What voltage is the battery bank ?
    What are the series fuse spec for the PV panels?

    You need a fuse to protect the wires, in case the controller fails and puts battery power into the PV wires.
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  • wastwast Registered Users Posts: 41 ✭✭
    mike95490 said:
    What voltage is the battery bank ?
    What are the series fuse spec for the PV panels?

    You need a fuse to protect the wires, in case the controller fails and puts battery power into the PV wires.
    batteries are 2x170 ah 24 volt  series spec for panels min  10 amp fuse
  • mcgivormcgivor Solar Expert Posts: 3,854 ✭✭✭✭✭✭
    edited July 2018 #4
    From the panels to the controller a 10A fuse would suffice, but I would recommend using a DC circuit breaker which is handy as a means of disconnect as well as protection. Likewise from the controller to the battery, pay attention to polarity on circuit breakers some are polarized, the positive terminal should be connected to the side with the highest energy potential, in a solar system with a battery, the battery is the source of highest potential. Now you're probably thinking fuses are cheaper, but when consideration to the cost of the replacement fuses, along with the holders are factored in, circuit breakers are actually cheaper and also provide a means of disconnect.

    Now the gauge of the conductors, 10 AWG is rated for 30A, so the maximum over current protection should be 30A, given the maximum current the system control supply is in the neighborhood of 13A from the controller to the battery at a distance of 5 feet to the battery, I'm assuming a typo in the OP, let's use a voltage drop calculator https://www.calculator.net/voltage-drop-calculator.html?material=copper&wiresize=3.277&voltage=24&phase=dc&noofconductor=1&distance=5&distanceunit=feet&amperes=13&x=74&y=17
    The voltage drop is 0.54%, well within limits, now it's up to you to use the calculator to establish voltage drop from the panels to the controller, since I don't know the voltage, but I'm sure it's well within acceptable limits of ~ 2-3%.
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  • wastwast Registered Users Posts: 41 ✭✭
    mcgivor said:
    From the panels to the controller a 10A fuse would suffice, but I would recommend using a DC circuit breaker which is handy as a means of disconnect as well as protection. Likewise from the controller to the battery, pay attention to polarity on circuit breakers some are polarized, the positive terminal should be connected to the side with the highest energy potential, in a solar system with a battery, the battery is the source of highest potential. Now you're probably thinking fuses are cheaper, but when consideration to the cost of the replacement fuses, along with the holders are factored in, circuit breakers are actually cheaper and also provide a means of disconnect.

    Now the gauge of the conductors, 10 AWG is rated for 30A, so the maximum over current protection should be 30A, given the maximum current the system control supply is in the neighborhood of 13A from the controller to the battery at a distance of 5 feet to the battery, I'm assuming a typo in the OP, let's use a voltage drop calculator https://www.calculator.net/voltage-drop-calculator.html?material=copper&wiresize=3.277&voltage=24&phase=dc&noofconductor=1&distance=5&distanceunit=feet&amperes=13&x=74&y=17
    The voltage drop is 0.54%, well within limits, now it's up to you to use the calculator to establish voltage drop from the panels to the controller, since I don't know the voltage, but I'm sure it's well within acceptable limits of ~ 2-3%.
      would this  be okay from contorller to battery  https://www.amazon.ca/Stereo-Circuit-Breaker-Inline-Holder/dp/B01EUHRSQW/ref=sr_1_4/137-2521514-8105920?ie=UTF8&qid=1530635359&sr=8-4&keywords=dc+circuit+breaker
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