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  • Solar and charge with alternator

    Trying to help guy build a system. We are planning to use a system very like this diagram i stole without credit from Sunking in another post. My buddy works out of town and stays in a small RV and was allowed to stay on job site as a "security guard" and plug into power, till insurance found out. He now has to drive 15 - 30 minutes away to park and can only use minimal lights. He on stays in the RV 4 nights a week and rides back home with rest of the crew. Our goal is to keep him in power for those 4-5 possible nights a week.

    He is wanting these 12 volt DC loads per day
    Cpap 8hrs 4 amps
    TV 8hrs 3 amps
    2 led lights 8hrs .5amps
    Propex heater 8hrs 1.9


    he is wanting these 120 volt AC loads per day
    Laptop 8hrs
    Microwave 700 watt 8 minutes 6.5 amps

    He would like to have an ARB fridge but not sure that will work out
    We estimated on a worst case scenario on time and amps as far as we know.

    I know this is alot of loads but what he said he has to have to be comfortable. The plan is 6 100 Renogy 12volt panels cause they will fit on the little RV. There is a possibility of using 800 watt but like to stay at 600. Use a MPPT and 225AH bank and using alternator to help charge. He is trying to get everything he can down to 12 volts to help and try to avoid using generator.

    Big questions

    1 where do you get the program to draw diagrams Sunking ?
    2 Assuming a 140 amp 12volt alternator would it make a difference in charging the bank in 15-30 min drive time?
    3 in diagram there is a label Sensij near controller on the 6 awg wire. What is Sensij ?

    Sorry if this is confusing and thanks for input.
    Last edited by 44toy; 11-19-2018, 08:07 PM.

  • #2
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    • #3
      Originally posted by 44toy View Post

      He is wanting these 12 volt DC loads per day
      Cpap 8hrs 4 amps: [COLOR=#B22222]12 volts x 4 amps x 8 hours = [B]384 Watt Hours[/B][/COLOR]
      TV 8hrs 3 amps: [COLOR=#B22222]12 volts x 3 amps x 8 hours = [B]288 Watt Hours[/B][/COLOR]
      2 led lights 8hrs .5amps: [COLOR=#B22222]12 volts x 0.5 Amps x 8 hours =[B] 48 watt hours [/B][/COLOR]
      Propex heater 8hrs 1.9: [COLOR=#B22222]12 volts x 1.9 amps x 8 hours = [B]183 watt hours[/B][/COLOR]


      he is wanting these 120 volt AC loads per day
      Laptop 8hrs: [COLOR=#B22222]Nonsense. Most likely the laptop uses about 20 watts x 8 hours = [B]160 watt hours[/B][/COLOR]
      Microwave 700 watt 8 minutes 6.5 amps: [COLOR=#B22222]700 watts x .133 hours =[B] 93 watt hours[/B][/COLOR]
      Total Daily Watt Hours = [B]1156 Watt Hours just call it [U]1200 watt hours[/U].[/B] Minimum battery requirement for RV 3-day reserve is 3600 wh @ 12 volts = 300 AH

      Originally posted by 44toy View Post
      I know this is a lot of loads but what he said he has to have to be comfortable.
      Oxymoron. To go solar means giving up comfort and a lot of money.

      Originally posted by 44toy View Post
      The plan is 6 100 Renogy 12volt panels cause they will fit on the little RV. There is a possibility of using 800 watt but like to stay at 600. Use a MPPT and 225AH bank and using alternator to help charge. He is trying to get everything he can down to 12 volts to help and try to avoid using generator.
      At 600 watts of panels into a 12 volt MPPT Controller will deliver 50 amps of charge current, and the smallest battery at that wattage is 300 AH. See the problem? Your battery is too small.



      Originally posted by 44toy View Post
      Big questions

      1 where do you get the program to draw diagrams Sunking ?
      Autocad or it can be done with Visio. Both are expensive. Visio use to be cheap until MS bought it.

      Originally posted by 44toy View Post
      2 Assuming a 140 amp 12volt alternator would it make a difference in charging the bank in 15-30 min drive time?
      You tell me. 12 volts x 140 amps x .5 hours = 840 watt hours. Drive or run the engine 1 hour a day and you can throw all the solar stuff in the garbage. as you would have no need for it. FWIW the panels would take all day to do what the engine can do in 30 minutes.
      Originally posted by 44toy View Post
      3 in diagram there is a label Sensij near controller on the 6 awg wire. What is Sensij ?
      Never touch the stuff. It is a PIA moderator that left 6-months ago.

      Forget the 800 watts of panels, a complete waste of money. 600 should be enough maybe, assuming the van is parked in full sun all day from sunrise to sunset with absolutely NO SHADE at any time, and is located in an area with a minimum 4 Sun Hours in winter which is very few places on earth.
      Last edited by Sunking; 11-19-2018, 09:49 PM.
      MSEE, PE

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      • #4
        [U][COLOR=#0066cc]Sunking[/COLOR][/U] I have one more question you mention "Drive or run the engine 1 hour a day and you can throw all the solar stuff in the garbage." The total AH used per day will be 100AH. Could driving the rig around with a 100-140 amp Alternator and isolator fully recharge the 100AH in 30minutes to an hour? No doubting your word just thought it would take 4-5 hours to charge the battery back.

        Comment


        • #5
          Originally posted by 44toy View Post
          [U][COLOR=#0066cc]Sunking[/COLOR][/U] I have one more question you mention "Drive or run the engine 1 hour a day and you can throw all the solar stuff in the garbage." The total AH used per day will be 100AH. Could driving the rig around with a 100-140 amp Alternator and isolator fully recharge the 100AH in 30minutes to an hour? No doubting your word just thought it would take 4-5 hours to charge the battery back.
          The engine is at least 5-10x as effective as solar. How much solar will you have to install to harvest 100ah @ 15V ? That would be 1500W of harvest for 1 hr, or 750W for 2 hours, or 300w of harvest for 5 hours. Notice I say harvest, not panels. Your roof top panels will be poorly aimed 90% of the time and I'd expect you need 600w of panels to get 300 w of harvest, and no clouds for 5 hours.
          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

          Comment


          • #6
            Sorry I must have confused the question in trying to type it. The question was, If you use 100AH per day and then drove the rig around with a 100-140 amp Alternator on it with isolator could it fully recharge the 100AH in 30minutes to an hour with out solar? I would have thought it would take 4-5 hours to charge the battery back up.

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            • #7
              Yes, how do you separate solar from the alternator charging ? If you were using the same battery (s)... I would assume a battery Isolator but how would you wire it ?

              Comment


              • #8
                You use an electronic battery isolator so your house loads don't deplete your starting battery .

                All charging sources connect to the battery. When using an isolator, the isolator has connections labeled.

                Using 100 ah, requires replacing aprox 120 ah back into the battery, there are losses, generally 20% with flooded, or 5% with AGM
                As a battery charges back up, it accepts charge at a slower and slower rate, till it is full. But the first 80% should charge up pretty quickly.
                To replace 100ah while driving, might take, in actuality, up to 2 hours. Solar would not go any faster, see my earlier reply for real world examples.
                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

                Comment


                • #9
                  Thanks again Mike, so no need to separate the charge controller from the alternator, again if using one battery, I get the house and starter system.. What I'm getting at is, if the alternator is running will the CC ignore it, or see the battery as charged ? I'm thinking they would interfere with each other.

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                  • #10
                    Originally posted by hunter29 View Post
                    Thanks again Mike, so no need to separate the charge controller from the alternator, again if using one battery, I get the house and starter system.. What I'm getting at is, if the alternator is running will the CC ignore it, or see the battery as charged ? I'm thinking they would interfere with each other.
                    Wait !! You do not connect the controller to the alternator wire. You connect your solar controller to the battery you want charged. And you place the proper size fuse at the battery to protect the size wire you are using.

                    The charge controller in daylight, would assist the alternator, if it's not charging the battery fast enough. That's going to require a pretty large PV array to "assist" the alternator.

                    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

                    Comment

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