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  • Low voltage cutout relay

    This is my first post. My first experience with solar was 30+ years ago when I installed a small solar array on my island cabin in N. Wisconsin. The battery array consisted of 2 golf cart batteries and served my purposes well, suppying enough power for lighting and a radio.
    Now I have recently completed a somewhat larger system for a recently built off grid cabin in S Wisconsin. It is performing quite well.
    The cabin is used intermittently, usually on weekends. It has a 500 watt array and a 2200wt inverter fed by 4 golf cart batteries. When I get to the cabin the batteries are usually fully charged. I use a countdown timer to shut off the inverter in case I forget to turn off something. (I also use timers on some of the individual circuits.) I also use a three way selector switch to power larger appliances so that only one can be energized at a time.
    I am considering installing a small 12V refrigerator or cooler connected in a new circuit off the battery bank. I would connect it through a low voltage cutout switch set at 12.5 or so volts. This theoretically would utilize my excess energy and keep a few beers cold for my arrival!
    Question: Is this a good idea and what would be a good cutout voltage for the relay.?
    Any help or suggestions would be appreciated.

  • #2
    Here's an excellent article on the subject of battery voltage levels:
    https://batteryuniversity.com/learn/...d_acid_battery
    This article says that, for long life, batteries shouldn't be allowed to drop below 2.05V per cell (12.3V) at room temperature. This threshold is lower at cold and higher at hot tempeature. Your choice of 12.5V will be good for battery life,
    The tougher question is whether this will result in enough cooling to keep the beer cold. That depends on the size of the fridge, the capacity of the batteries, the amount of sun you get, etc. But it's worth a try!
    7kW Roof PV, APsystems QS1 micros, Nissan Leaf EV

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    • #3
      Thanks for responding. I will give it a try starting at 12.5V and then go lower if necessary. I was amazed to find that the relay with digital readout is available on Amazon for only $13.99. (IS Icstation Digital Low Voltage protector disconnect switch) [h=1][/h]

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      • #4
        Originally posted by Chip View Post
        Thanks for responding. I will give it a try starting at 12.5V and then go lower if necessary. I was amazed to find that the relay with digital readout is available on Amazon for only $13.99. (IS Icstation Digital Low Voltage protector disconnect switch) [h=1][/h]
        Some of those devices are limited in the Amperage they can handle. If your beer cooler comes close to that limit you may want to consider a separate relay in your plans.

        9 kW solar. Driving EVs since 2012

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