What do I do with solar system while gone for extended periods?

McsapMcsap Registered Users Posts: 5 ✭✭
I have a cabin in the Upper Peninsula that I use 3-4 times a year.  I bought a Renogy kit with 2 100W panels and one 30A PWM Wanderer Charge Controller to maintain 2 marine batteries to power various 12v appliances.  The question I have is, what do I do with the system when I leave?

I want to take the batteries with me, especially in winter, when it gets well below freezing.  I don't like the idea of leaving batteries hooked up to a camp in the remote woods.  If the controller malfunctions, it could start a fire.

Tech support for Renogy said I can just leave everything else hooked up, just leave the battery cables separate from each other.  This doesn't seem particularly safe to me.  Those cables will have power, could they arc somehow?

I've read that I can disconnect the panels, but I plan to put them on the roof, and don't really want to climb up and down to connect and disconnect them.   Is there a shut off switch I could install in between the panels and the controller?

I guess what I am looking for is a simple way to "shut off the juice" to inside the cabin while I'm gone for months at a time for my peace of mind.  

Also, Renogy said nothing about grounding my cabin.  Is that necessary?

Thanks very much.

Comments

  • PhotowhitPhotowhit Solar Expert Posts: 5,827 ✭✭✭✭✭
    No chance of the panels shorting out and catching fire assuming you are running a 12 volt system. 12 volts DC will not arc, even at VMP voltages and arc would be tiny and you would not be able to put combustible material near enough to catch fire. Slightly more dangerous, think going from 0 to .000000000001% chance if they are configured as a string and running to a MPPT type controller.

    If you di a correct setup, you have the solar panels run into a breaker just before the charge controller. Just open that breaker and all is well.

    FWIW - Marine batteries are a poor choice as they are rarely true deep cycle batteries...
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
  • McsapMcsap Registered Users Posts: 5 ✭✭
    Thanks very much.  

    Yeah, I've learned that the marine batteries were not the way to go.  Will definitely upgrade next time.

    Do I need to ground the building?  I'm guessing it's unnecessary?


  • PhotowhitPhotowhit Solar Expert Posts: 5,827 ✭✭✭✭✭
    Mcsap said:
    Do I need to ground the building?  I'm guessing it's unnecessary?
    Always safer, but for the small system you have now I would be comfortable 'floating' the system.
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
  • BB.BB. Super Moderators, Administrators Posts: 32,642 admin
    edited April 14 #5
    Grounding (via ground rod/cold water pipe, etc.) is there to help safely direct lightning strike energy to the earth... And not have it find its own way to ground inside the cabin.

    https://ecle.biz/lightning-risk-map/

    Grounding (and surge protection) is there to both help prevent injury and protect your equipment. Nothing will stop a direct strike form causing damage... But grounding will help.

    Also, depending on your cabin's orientation to prevailing winter winds and drifting snow... Some folks have used a small solar panel (1-2% rate of charge + small/simple charge controller) vertically mounted to an exposed southern wall, or vertical on roof (to shed snow) to trickle/float charge the batteries in winter.

    In general, Flooded Cell Lead Acid batteries need charging at least once a month at ~77F... However, for banks that are less than 32F during winter--The self discharge rate slows down a lot and the bank can easily go >4 months without charging (for every 10C/18F below 25C/77F, battery aging and self discharge drops by 1/2... At 5C or 20C below room temp, that is 1/2*1/2 = 1/4 aging/self discharge rate.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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