additional portable battery to charge excess energy, how??

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  • bjornderian
    Junior Member
    • Feb 2019
    • 1
    #1

    additional portable battery to charge excess energy, how??

    I have a PV system and a lead acid battery bank (48V) already attached with an MPPT solar charge controller. I want to charge a portable Lithium ion battery (24V) using excess energy during the day.

    Is it possible to charge the portable battery without going through a dc to ac inverter and another ac to dc charger which would decrease efficiency? basically, charging directly from DC with another battery already attached to the charge controller.

    SInce I will be charging the li-ion only when the lead acid is full, what device would I need to shut off the connection to the lead acid and switch to the dc to dc controller-> li-ion charger automatically?

    If it's possible, how? and what do I need
    Tags: battery, charge controller, efficiency, excess, off grid
    • Mike90250
      Moderator
      • May 2009
      • 16020
      #2
      Nope. Li batteries are really picky about being charged just right, otherwise, you get a fire. You have to use factory recommended charging gear.

      You could configure a small morningstar MPPT controller to run from 48V and have custom setpoints for the Li battery, but you have to have the right setpoint voltages, which the salesdroids on the internet have no clue about.

      And only the midnight classic controller has a " waste not" output signal for a full battery. otherwise you are mcgivering something up out of parts, that might work for a while
      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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