Trying to design winter battery storage system

rp3703rp3703 Registered Users Posts: 123 ✭✭

I finally updated my signature line so I wouldn’t have to keep describing my system every time I posted on here. That will save me a paragraph. Anyhow, in a previous thread it has been suggested that I leave my batteries on a separate, vertically mounted panel with small charge controller to keep them alive through the winter since the regular roof mounted panels could get covered in snow for 2-3 months straight. Bill (BB.) even did the math for the suggested panel size. A lot of the contributors suggested I just cut everything off and let them sit since the cold weather will slow their rate of discharge as long as they are at float when I leave but it was pointed out that there will still be 2-3 warm months after I leave and 1-2 warm months before I return that the batteries will be sitting. If the batteries would be fine sitting at float for 2-3 months of below freezing temps, would I not just be able to use one of my regular roof mounted panels (2˚ pitch roof) and just run it into a small charge controller to keep the batteries alive till the snow hits. Then the batteries would be sitting with no charge until the panel clears off 2-3 months later. I realize the concern was that the charge controller could pull enough power on it’s own to draw down the batteries but do they not make one that does not use power when no power is being produced by the panel?

1860 W (6) Rensola JC310M, Classic 150, [email protected] (8) Deka DSGC15 FLA's, Victron Phoenix Multi 24/2500 Inverter
Powering-20.5 CuFt. Fridge, 1 HP Submersible water pump, UV, Washing Machine, Gas Dryer, Gas Stove, Lights and Receptacles
Off Grid Cottage on lake in Northern Ontario 46˚N 


  • EstragonEstragon Registered Users Posts: 4,451 ✭✭✭✭✭
    Mppt controllers, like the midnite classic, will tend to have higher idle consumption that a small, simple, pwm controller.

    In the case of a classic, idle will be ~3-5w. Doesn't sound like much, but even at 3w, thats 3x24x30=2160w/month. A pwm controller would typically be much lower.
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
  • mcgivormcgivor Solar Expert Posts: 3,274 ✭✭✭✭✭
    Shutting everything down means not much could go wrong, as long as the batteries were fully charged when leaving, cold is your friend in this case, basically  putting them to sleep, or hibernation if you like, this will minimize self discharge. Sometimes less is more.
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery bank 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah FLA 24V nominal used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
  • mike95490mike95490 Solar Expert Posts: 8,616 ✭✭✭✭✭
    it all depends on the self-consumption of the charge controller.  A 20 MPPT from Morningstar consumes less than the Classic, and a PWM even less. 
    Powerfab top of pole PV mount | 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

    gen: ,

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