Newbie needs help

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stepbanstudio
stepbanstudio Registered Users Posts: 2 ✭
in Solar Beginners Corner #1
I have a renogy 100 W panel, a bestek 2000 W inverter that a friend gave to me, 2 Deep cycle marine batteries, and I want to get an MPPT controller. This is where I get confused so I have 100 W, I’m using 12 V batteries,  I have a 2000 W inverter,  now what size mppt do I get? 10, 20 or 40 amp?
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  • Photowhit
    Photowhit Solar Expert Posts: 6,003 ✭✭✭✭✭
    #2
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    Well... you can't really use a MPPT controller efficiently with a single 12 volt nominal panel. You would be better off with a PWM type charge controller.

    As to the size of charge controllers, they are generally based on output current. So your single 100 watt panel will output about 6 amps at 17.5 volts. so 10 amp is all you need for it. Often people will buy larger controller in anticipation of increasing the size of their system.

    I'd suggest marine batteries are generally not the type of deep cycle battery you need. You would be better off with golf cart batteries. It a question of metal alloys used. Also you would want a balanced system. If your 12 volt batteries are pretty small, say group 24, they may be only 65 amp batteries so in parallel they would represent a 130 amp hour battery bank. You would want a charge rate of 5% or so for weekend use of your system, or around 6.5 amps. For daily use, I'd suggest a minimum of 10% charging capacity or 13 amps. If they are larger batteries even larger array would be suggested.
    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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  • BB.
    BB. Super Moderators, Administrators Posts: 33,447 admin
    #3
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    From the duplicate thread:

    mike95490 
    your panels do not need a MPPT controller, be happy you can use an inexpensive PWM controller.   After 300-400w, with larger panels in the +200w size MPPT becomes more practical for it's expense.

    -Bill "moderator" B.
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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