adding second Classic 150 charge controller - diodes needed?

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BenA
BenA Registered Users Posts: 15 ✭✭
edited September 2016 in Advanced Solar Electric Technical Forum #1
Have an off grid system with a maxed-out Midnite Classic 150 charge controller (~2kw PV).  I want to add another kw of PV thru another classic 150.  The second classic will be feeding a second battery bank with different charging specs than the main battery bank (both banks are 24v).

How do I charge these battery banks separately but combine their power output to power the Magnum inverter?  Diodes or some type of selective path circuit?  Any advice, thumbnail sketch or schematic would be much appreciated.
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  • Photowhit
    Photowhit Solar Expert Posts: 6,003 ✭✭✭✭✭
    #2
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    In general, you just don't. It will only create problems with the inverter drawing from one bank more than the other.


    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
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  • BenA
    BenA Registered Users Posts: 15 ✭✭
    #3
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    I see you have a number of charge controllers.  All of them are feeding a single bank of forklift batteries?  I'm told it's a no-no to mix batteries or even different ages of the same battery -- how do you handle pack expansion?
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  • Photowhit
    Photowhit Solar Expert Posts: 6,003 ✭✭✭✭✭
    edited September 2016 #4
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    No, just 2 feeding one forklift battery. Likely 3, if I ever finish, though more for cloudy day charging.

    If you try to draw energy from 2 battery banks for one inverter, they won't draw evenly. If you must use 2 battery banks, you might have them switched, so perhaps one is used until you turn in for the night and then you switch to the other to run the rest of the night. Just not very easy to share the load, but in that case you can just have the charge controllers set up, one for each bank and not worry.

    I'll 'expand' and likely switch to 48 volt system when this battery dies, or if it shows signs of weakness, before the 30% tax credit ends. It's 5 years old and doing nicely now.
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
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  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    #5
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    Is someone selling Diodes ?  In the last 2 months, all sorts of goofy diode questions have been popping up.  Maybe some clueless blogger is pushing them for some reason.  
    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

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

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