Morningstar MPPT Charge Controller Setup Question SS-MPPT-15L

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chetwynd
chetwynd Registered Users Posts: 4 ✭
in Off Grid Solar & Battery Systems #1
Hi, I have two questions.

1. I think the max input wattage for the SS-MPPT-15L is 200 watts, right? I have a 240 watt panel plugged into it because I got a great deal on the panel. So, what happens if it gets above 200 watts? And, if it's a problem, can't I just drape a towel over part of the panel to get it to produce less? This is for a small travel trailer that I have (Scamp) that has two 12 volt batteries that I want to keep charged when I'm out camping.

2. I have everything all set up now in my driveway and the panel is only getting partial sun for part of the day, which is fine by me. The remote meter that I also bought is showing something like 13.4 volts, but my question is - what exactly am I looking for? How do I interpret the voltage numbers?

THANK YOU!
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  • firerescue712
    firerescue712 Solar Expert Posts: 95 ✭✭
    #2
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    Re: Morningstar MPPT Charge Controller Setup Question SS-MPPT-15L

    The MPPT15L will only put out 15 amps. Regardless of how many panels or amps come in, it will still limit the output to 15 amps. The charge controller will take the total input from the panel and convert it to 12 volts. It will maximize the charge with the larger panel.
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  • rgk1
    rgk1 Solar Expert Posts: 134 ✭✭✭
    #3
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    Re: Morningstar MPPT Charge Controller Setup Question SS-MPPT-15L

    I had mine hooked up to 2 - 135 watt panels for 270 watts (theoretical). Though I didnt really have a way at the time to see what the panels were producing real world, I never had any problem. Used it most of last year.
    4-Risen 320 watt in series/parallel, 8-215ah 6 volt GC2 batteries in series, Exeltech 1100 watt/48 volt inverter, Tristar 45 MPPT controller.
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  • Eric L
    Eric L Solar Expert Posts: 262 ✭✭
    #4
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    Re: Morningstar MPPT Charge Controller Setup Question SS-MPPT-15L

    Like firerescue said, it's output limited to 15 amps, so you need to think of those amps times the charging voltage. If one of your 12v batteries is charging at, say, 14.4 volts, the controller will charge with more than 200 watts, provided that your panel can actually deliver that much. If your two 12v batteries were wired in series, for a 24 volt bank, the Morningstar could deliver over 400 watts at a charging voltage of, say, 28.8 volts.

    I doubt you'll have a problem with that one panel, even with a 12 v battery.
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  • Windsun
    Windsun Solar Expert Posts: 1,164 ✭✭
    #5
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    Re: Morningstar MPPT Charge Controller Setup Question SS-MPPT-15L
    firerescue712 wrote: »
    The MPPT15L will only put out 15 amps. Regardless of how many panels or amps come in, it will still limit the output to 15 amps. The charge controller will take the total input from the panel and convert it to 12 volts. It will maximize the charge with the larger panel.

    This BTW, makes it great for charging 12 volt batteries from 24 or 36 volt systems also :)
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  • bmet
    bmet Solar Expert Posts: 630 ✭✭
    #6
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    Re: Morningstar MPPT Charge Controller Setup Question SS-MPPT-15L

    Shading is something to be avoided at all costs. Help me out here, Admins.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,439 admin
    #7
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    Re: Morningstar MPPT Charge Controller Setup Question SS-MPPT-15L

    You should have no need to shade your panels with an MPPT controller. And it would be a bad idea anyway. Shading can dramatically reduce solar array outputs (towards 0 amps), and can cause other stresses inside the array).

    To give you an idea--Here is a Video this nice thread from Kevin in Calgary Canada that shows designing and installing solar PV in a small RV trailer (with the MorningStar 15 amp MPPT controller). Kevin did post a back in January saying that the system is still working very well for him.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #8
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    Re: Morningstar MPPT Charge Controller Setup Question SS-MPPT-15L
    bmet wrote: »
    Shading is something to be avoided at all costs. Help me out here, Admins.

    you are right in that shading should be avoided, but let's face it, it's a fact that our pvs get shaded at some time. you don't want to deliberately shade a pv unless you are doing it for safety reasons as in preventing possible shocks, arcs, or damage to equipment. it should not be done to purposely be in a design to keep power capacities in line. in general, do avoid shading issues as much as possible though as it is the enemy of producing power from your pvs. at all costs is an expression for i will not buy my neighbors property just so i can cut down trees there that may shade my pvs. common sense, no?

    they give a limit to the pv wattage as you don't want to have power wasted either for what good does it do to have for example 300w of pv to a 200w inverter that won't output it all? at the same time one would like to take advantage of the abilities of the inverter for you wouldn't be happy with just say 100w when it could do better, but one consolation is that it won't get cut off of its full potential due to max limitations.
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