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Ideas with some hypothetical numbers for extended boon docking in RV

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  • #31
    Originally posted by zamboni View Post
    Do you drive a car?
    many are full of Gasoline, which is QUITE explosive. FORD found that an expensive lesson, using a gas tank as a bumper.
    Treated properly, over 30 years, gasoline tanks are much safer now. Cars mostly blow up in movies only.

    I have no doubt as the Li battery tech matures, they will become safer, but currently, they are not recognized as safe as AGM batteries.



    Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister

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    • #32


      I am back again for an update!
      The system is up and running. 1600 watts of non tiltable solar, 3 strings of 3 180 watt 12 panels. Victron Solar charger(150/85) to 300AH 24 volt bank of 4 Lifeline 6v 300AH batteries. Victron 3000 multiplus hybrid inverter into trailer panel. There is a Victron Venus GX and 712 battery monitor.

      I am not happy with the battery monitor as the voltage and the SOC is wrong. It will say 84% SOC and voltage is 24.94V. I am pretty sure that the battery bank is not getting completely charged. There is no draw without going through the shunt so I am sure it is on of the settings. I did not notice a problem until I am completely reliant on solar for battery charging.

      The solar charger settings were:
      Absorption - 28.6
      Float - 26.6
      temp compensation - 20mV/degree C

      I change to generic AGM settings:
      Absorption - 28.8
      Float 27.6
      Temp compensation 32.4mV/degree C
      And now the absorption charging looks closer to what Lifeline wants it to be.

      Is 'tail current' for battery monitor settings = in absorbtion when the current drops below 0.5% of the battery

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      • #33
        Originally posted by Treejohnny View Post
        I am not happy with the battery monitor as the voltage and the SOC is wrong.
        Of course it is wrong and will never be right. It is not possible to determine battery SOC from voltage. You wasted your money. Get rid of and sell it to a Sucker.
        MSEE, PE

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        • #34
          I have been reading a bunch from the off grid section about AGM batteries and it appears as though my battery monitor is very expensive voltmeter....I had much higher hopes of with the addition of a shunt.

          Should I start new post there?

          So I have read Lifeline's Technical papers on their battery, Victron's manuals about setting up their solar charger and battery monitor. Maybe my issues is from when I was in IL and clouds interfering with Absorption and Float cycles and not charging my battery to '100%' SOC. After all that I have read so far, I believe that I should set my solar charger to equalize/condition the lifeline batteries every 2-4 weeks for about 4 hours, this seems weird for AGM to me.

          We are living in the trailer now. I bought a Honda 2200 inverter generator for cloudy days but I have only used it for testing after leaving the midwest. I pull trailer with Chevy Duramax, it has 12V system with 2 batteries and the ability to easily add second alternator. Maybe someone sells 24V alternator to just charge house batteries? The house batteries are 24V but I could make 12V leads to connect to truck, this would bypass the shunt for battery monitor, not sure if that matters now. This would allow me to sell the generator and free up a little room and stop carying gas can. With 2/0 wire from truck to house battery I could start truck from trailer battery or bulk charge trailer from truck. I also have a good jump pack to start truck if everything is dead. Of course I could just wait for solar to charge battery as well since I am already home.

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          • #35
            Tree Johnny the issue is you cannot work around Pb batteries charge-discharge efficiency. It is a moving target hour by hour. There is no algorithm anyone can write to take into account all the variables, especially if they change hour by hour. It would require calibration and changes in algorithm every stinking day. Yes you bought a very expensive $10 volt meter.
            MSEE, PE

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            • #36
              flexible psanels
              Originally posted by Mike90250 View Post
              b) Lithium batteries (much lighter weight, and less mature tech)
              I'll be using a 30AH lithium battery in my camper shell. Two flexible 100-watt panels.

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              • #37
                Originally posted by Mike90250 View Post

                many are full of Gasoline, which is QUITE explosive. FORD found that an expensive lesson, using a gas tank as a bumper.
                Treated properly, over 30 years, gasoline tanks are much safer now. Cars mostly blow up in movies only.

                I have no doubt as the Li battery tech matures, they will become safer, but currently, they are not recognized as safe as AGM batteries.


                Disagree but that's ok. My problems with lead-acid, aside from the weight, are the lead and the acid, and the gases they produce. I'll use lithium. 12v, 30AH in a camper shell. Lead-acid is *ancient.* Not for me. at least not in the shell.
                Last edited by Old_Man; 01-17-2023, 12:07 PM.

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                • #38
                  Originally posted by Treejohnny View Post

                  Mike - I have seen a couple of threads that talk of the LFP batteries but when I search on google the batteries cost more than AGM and that is not including the BMS. Unless I am missing something?
                  You appear to be missing the fact, lifepo4 batteries let you take them down to 10 percent SoC without damage. Try that with any flavor of lead-acid. Those batteries die quick anyway, even faster when damaged.

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                  • #39
                    Originally posted by Old_Man View Post

                    You appear to be missing the fact, lifepo4 batteries let you take them down to 10 percent SoC without damage. Try that with any flavor of lead-acid. Those batteries die quick anyway, even faster when damaged.
                    I still think you have to do the math concerning how many watt hours you can get out of the battery's life and what it cost per kWh. Li chemistry does allow for deeper discharges but the initial cost may be very high and in the end the cost per kWh is also higher then FLA type batteries.

                    Do the math and not be fooled into thinking one battery chemistry is better then others.

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                    • #40
                      Why? Why do I have to do that? I did my energy audit and the battery I'm buying is (at least on paper, for now) is up to the task.

                      I like using newer technology. I was an early-adopter of Mac computers. Lifepo4 has been around a long time, so I don't feel like an early-adopter in this case.

                      I like the light weight of Lifepo4, I like the small size of the Lifepo4 battery I'm buying (fits in the palm of my hand), I like the ease of using one battery. And later on, I may buy a larger battery if this battery proves woefully inadequate. But only one. Time will tell. But I'm going Lifepo4 right away. Only lead-acid I'm interested works the starter on the truck. And I have a small solar panel to charge the truck battery when it's sitting.

                      I just hope the water clears soon enough that there will be some good trout fishing in California.
                      Last edited by Old_Man; 01-18-2023, 11:19 AM.

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