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  • Multiple charge controllers for one battery bank

    I currently have one 330watt solar panel hooked up to a MPPT controller that is charging a 12V 300AH LifePo4 battery bank in my camper conversion. Would it be possible to connect a second MPPT charger controller to a second (smaller) solar panel and charge the same battery bank with both charge controllers efficiently?

    Thank you

  • #2
    I believe so. It has been my original plan to connect two pairs of 150W panels through two MPPT controllers and I've discussed this at length with the so-called [I]experts[/I] at the electronics shop. In fact they even sold me a pair of 180W MPPT controllers originally, until I returned them and swapped them for a single 360W MPPT controller which seems to be more suitable at this stage - the option being to purchase a second 360W MPPT controller if the single one already installed doesn't seem to be able to handle the current from the 820W panel total.

    LiFePO4 is a concern. I am running good old-fashioned SLA batteries (2 x 100AH) and they don't mind a range of controllers all working together for the same good cause; keeping them charged. LiFEPO4s are apparently quite temperamental about anything they can find to be so about. I can't see it making much of a difference though, because if one MPPT controller is charging them happily, then a second MPPT controller is only going to double the fun, isn't it?

    How can the battery tell whether the incoming power is from one MPPT controller on a sunny day or two MPPT controllers on a cloudy day? The wiring is analogue, not digital. There is no such 'smart-meter' kind of system in these setups. All they can really measure is the levels of volts, amps, watts as far as I know.

    PS: Please understand that I am writing theory which I have yet to test in practice, with the two(2) MPPT controllers connected to LiFEPO4 batteries. I am hardly one of the experts, and probably should have refrained from posting a reply, but I was half asleep and there had been no replies at the time, so dived in trying to be of some use to this forum which has been of much help to me in this past week.

    Do not take my words as the definitive expert advice. Please wait for confirmation before proceeding.
    Last edited by Seano; 03-15-2019, 11:47 PM. Reason: Post script disclaimer because I only know what I am writing about in theory, but not yet in practice.

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    • #3
      Multiple charge controller are a perfectly fine configuration. Beware under sudden sunny conditions, you can exceed recommended battery charge rates
      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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      • #4
        Originally posted by Mike90250 View Post
        Multiple charge controller are a perfectly fine configuration. Beware under sudden sunny conditions, you can exceed recommended battery charge rates
        The batteries are Battle Born 100AH and as far as I know the charge rate for them is 1C, I'm not expecting that to be an issue with the amount of solar panels I'm putting up (330-660 watts). Is there another issue I should be concerned about?

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        • #5
          thezenvan, what settings are you using on your charge controller for the Battle Born batteries? Are you doing an absorption charge or just bulk and float?

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          • #6
            Originally posted by 685eric View Post
            thezenvan, what settings are you using on your charge controller for the Battle Born batteries? Are you doing an absorption charge or just bulk and float?
            I currently have an Outback FlexMax60 charge controller. It's setup with bulk and float using the parameters in the manual for Lithium batteries

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