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  • fishtait
    Thanks for your comments. I am leaning toward getting an AGM battery but also considering lithium ion, although the cost is probably too much. Do you have a reference for estimating the percentage of power remaining at various voltages, i.e., at 12.5V there is x percentage of power remaining? I'm sure that a chart exists somewhere but I don't know where. Thanks again
    June 8
    • pthomas745
      I have a 2017 trailer, and a 3 way fridge. Consequently, I don't really have the need for bigger batteries. I have the stock 80 amp hour battery that came with the camper. I will soon change it over to a new AGM battery of 100 amp hours.
      This is the basic battery "best practice for longest life" idea for an AGM or lead acid: if you keep your state of charge for a battery above 50 percent, you will get the most charge and discharge cycles from it. You can go lower sometimes....but the more times you crash your battery into the 20 percent mark...the faster it will quit.
      So, for my 80 amp hour battery, every 10 percent of the state of charge chart equals 8 amp hours.
      12.5 means I've used 8 amp hours, so I have 32 left.
      12.4 means I've used 16 amp hours, so I have 24 left.
      12.3 means I've used 24 amp hours, so I have 16 left.
      12.2 means I've used 32 amp hours, so I have 8 left.
      12.0 means I've used 40 amp hours......so I'm down to the limit for "maximized battery life."

      Batteries are the weirdest thing: nothing about them is hard and fast. They are still "old tech", and, as such, have many caveats. Every one of the numbers I put up there...are assumptions and guesses! Not bad guesses, but, guesses. The process above is what I went through when I first bought the trailer and learned how to use a multimeter, and before I got really comfortable with my solar panels.
    • rrcbov
      Some objective info in this utube