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Thread: Charging 12V Battery with 24V Solar Panels

  1. #1
    Junior Member
    Join Date
    Jul 2012
    Posts
    4

    Default Charging 12V Battery with 24V Solar Panels

    Hello everybody,

    I've been looking around for 2 new solar panels for my house. I was looking for something in the over 200W range, like two 235W or something similar. I already have a big 12V Battery, and also some other 12V equipment like inverters, fridge and lighting which I would really like to keep. Now I've realized that pretty much all the big panels are 24V or even higher. What would be the most reasonable solution for this? Of course it makes a lot of sense for them to run a higher voltage as it helps a lot in wire size, but I don't want to get into setting up a whole new system.

    I've already heard people talk about mppt controllers like the Tristar MPPT 60A being able to work with higher input voltages and being able to charge 12V batteries. Would there be another solution for my problem, or would a MPPT controller the only way to go? I already tried to understand the specs from the Tristar, but could not completely follow. Do I understand correct that I can have voltages up to 150V to charge a 12V battery but only with a total wattage from the panels of 800W?

    My last question would then be: My friend has run his solar panels over 3 charge controllers to the same battery because he has added on to his system over the time. He is very picky with his system, and it has worked well for him that way. So would it theoretically or rather practically be possible for me to go with the Tristar 45A for my two 235W 24V Panels in series (to cut down wire size) charging my 12V battery, and if I need to add on to my system in the future, buy another Tristar 45A and two more 235W 24V Panels charging the same battery with the two setups?

    Question over questions. It all seems really simple at times, but then it gets me again . If it would be possible to use individual charging setups like my friend uses that would be really great as I wouldn't have to predetermine the total size of my future system as it might grow . And also it would give me some security in case something brakes on one system I could still keep the other part running while I fix the other one.

    I'm really looking forward to your responses! Thank you for your help!

    Aleman83

  2. #2
    Moderator
    Join Date
    May 2009
    Location
    off grid retirement in Northern Calif
    Posts
    7,466

    Default

    With over 400W of PV, and the amount of investment for the Tristar MPPT's, I'd seriously look at the Midnight Classic Lite, in the $500 ballpark (search the web), which you can monitor and control with a PC.
    Since the dawn of time it has been mankind's dream to blot out the sun.
    Montgomery Burns

    "Always listen to experts. They'll tell you what can't be done and why. Then do it."

    spreadsheet based voltage drop calculator:
    http://www.solar-guppy.com/download/...calculator.zip
    http://www.solarpaneltalk.com/showth...oss-calculator

    http://www.mike-burgess.org/PVinfo_2.html

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,
    battery lugs http://tinyurl.com/LMR-BigLug
    Setting up batteries http://tinyurl.com/LMR-NiFe

    gear :
    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 || || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

  3. #3
    Member
    Join Date
    Jun 2012
    Location
    Norway
    Posts
    76

    Default

    If you stick to the Tristar brand I would have selected the 60. It has got the web interface and you dont need to buy the optional display. Configuration is much easier done with a computer, and it's kind of fun to be able to monitor power production remotely.

    If you google the product you will find some good documentation which might help you to decide. I believe there even exist a 60min training program for Dealers on Youtube.
    --------------------
    Norwegian off grid cabin owner
    Panels facing south

    - Kyocera panels 135W
    - Tristar 60A MPPT
    - Victron 3000w/12V / 120A

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