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-Idea- Connect: Car engine+SolarPanel+Generator into MPPT controller?

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  • -Idea- Connect: Car engine+SolarPanel+Generator into MPPT controller?

    Would be great to use all these different sources of energy readily available in an RV/Van Conversion off grid setup... and simply attach them to an mppt controller's solar input, so they be best equalized to charge a battery.

    In theory, I think this should work as long as all the sources are:
    1. DC
    2. (summed) within the controller's max V input and A charging capacity
    3. (summed) within the battery's max continuous charging capacity

    But I wonder if them having different voltages would be a problem for the controller. Usually a controller can down-convert a higher voltage to a battery's ideal charging voltage, increasing the amps. But if several electrical currents were meeting at the same location (a battery terminal multiplier attached to the controller's pv input, like this one I don't know if they'd all be equalized to 12v or if something would explode.

    some generators have a 12v 8a output which is perhaps too small to power batteries over 200ah, but perhaps you could take the generator's ac output through an ordinary AC/DC adapter, and then attach the bare wires to the battery terminal on the charge controller...

    as far as the car engine, i've heard people using an isolator to charge their secondary battery bank while the car is running but avoid the car battery from being drained when the car is off. Would anyone be able to explain this more in detail?

    All in all, it seems a nice thought to be able to charge your off grid battery every time you drive, every time the sun shines, and every time you run your generator, without making constant changes in your configuration. If this is appealing to you, please add your ideas.

    About me: I've given my landlord a 30 day notice to move-out and will be soon living in my conversion van. Joining this forum and starting this discussion is part of my education process. All input appreciated. Thank you.
    Last edited by Micole; 11-23-2016, 06:38 PM.

  • #2
    You don't want to run the engine alternator or generator through an mppt. You can ( and most do ) connect them to the battery for charging. There is no reason you can't have multiple sources charging a battery.
    It sounds like you are trying to solve a nonexistent problem.
    OutBack FP1 w/ CS6P-250P


    • Micole
      Micole commented
      Editing a comment
      If im trying to solve a nonexistent problem, then how come I've never read a forum post of someone doing this before? Or would you say connecting several, non-solar DC sources into an MPPT controller is common practice? I think not.

      Sure, perhaps the specific methods to complete this idea don't need new inventions made, or custom work. But nevertheless, I think ideas like this are worth sharing for others to learn new possibilities.

    • Micole
      Micole commented
      Editing a comment
      yeah i thought I'd simply connect a +- cable pair from the car battery into the MPPT input terminal, but not sure how to keep car battery from draining when engine is off.

    • ButchDeal
      ButchDeal commented
      Editing a comment
      Do not put anything other than solar into the mppt charge controller. Connect the house battery to the alternator with an isolator which will keep the engine battery from being drained. You can also connect the generator battery charger leads to the house battery. This all three sources are charging the battery,

      The reason you do not read about people using a solar charge controller to connect an alternator to a battery is because it is a bad idea, and is not needed.

  • #3
    Grab a CTEK D250S charger / isolator. It will do what you want with a minimum of fuss. Popular with offroad / 4x4 / Rv crowd with alternator, isolator, and mppt charger with dedicated solar input all in one. Done!


    • Micole
      Micole commented
      Editing a comment
      It looks like the perfect product to put this all together. Except that I have a 200ah 12v lithium battery.

  • #4
    A Solar MPPT controller is only going to work with SOLAR panels. Midnight has a clever workaround to map a wind turbine (model specific) power curve into a MPPT controller and load the turbine to the optimal level. Much of what a MPPT controller does, is to track the solar harvest right to the edge of voltage collapse point. You can't do that to an alternator, or transformer without cooking something in a bad way.
    As others have said, combining many sources to 1 battery bank is quite doable.
    Blending several sources into a Li battery will require some good engineering to keep things safe and not kill the battery
    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



    • #5
      Originally posted by Mike90250 View Post
      Much of what a MPPT controller does, is to track the solar harvest right to the edge of voltage collapse point. You can't do that to an alternator, or transformer without cooking something in a bad way.
      The other problem when trying to use MPPT with wind turbines is that as the current drain is increased the voltage will initially drop only slightly. But in the longer term (seconds) the turbie will slow down since you are pulling more power from the rotating mass than the wind on the blades can replace. The eventual result is indeed voltage collapse.
      The opposite effect happens as you decrease the current, if the MPPT scan goes in that direction. The voltage initially stays relatively constant and then after some seconds rises as the turbine speed increases.
      SunnyBoy 3000 US, 18 BP Solar 175B panels.


      • #6
        "Works" has two definitions. 1. It is not going to blow up. 2. It will do anything useful. A car battery is bulk charged and fixed at no more than 14.5V. If the solar panels have a power point of 16V, nothing will be added from the car. Much the same as with another parallel panel with a couple of shorted cells and a lower voltage. That also applies to the generator depending how well regulated it is. If a simple transformer charger connected to the generator with high IR losses, there will be some adding. In short all three will work individually but you will not get the most possible out of each one if connected together.