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Rv_Adventure_Couple
Rv_Adventure_Couple Registered Users Posts: 29 ✭✭
in Solar Beginners Corner #1
Okay before I lay out my problem I will lay out what equipment I have.
On the roof of our rv I have 4-200 watt solar panels. 2 sets of series then in parallel.
Our charge controller is a 150/40 amp Mppt epever tracer with the MT50 display to program
The MT50 Display says I am pulling in 40.3v pv at 8.4amps and the mppt is converting it to 14.3v at 23.7amps, but only 341 watts.

Okay so the problem is the MT50 is telling me that I am only pulling in 400 watts at most. I unhooked one of the series sets of panels and was only operating on 2 panels in series and the MT50 said I was pulling in nearly 300 watts. I then unhooked that series and connected the other series and got the same performance. The sky is clear and the sun is directly over head. So why when I hook them both up am I not seeing 600 watts but only 400ish.

Thanks in advance
Rv Adventure Couple
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  • Marc Kurth
    Marc Kurth Solar Expert Posts: 1,187 ✭✭✭✭
    #2
    "Pulling" is the keyword. If you don't have a load, you won't "pull" the power. For example, a full battery bank "pulls" very, very little power.
    Turn on some loads and run your battery bank down to see if you produce what you expect.
    I always have more questions than answers. That's the nature of life.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,696 admin
    #3
    What is the battery bank charging voltage set point... For Flooded cell batteries, it is typically around 14.75 volts (@ 75F). And for AGM/Sealed batteries, typically around 14.4 volts

    If your battery is at 14.3 volts, and the set point is 14.4 volts (AGM/Sealed), then the battery bank is probably >80% full, and "naturally throttling" (battery limiting) charging current.

    By the way, what is the Vmp rating for your panels? 40 Volts for 2 in series (~20 volts Vmp operational) for 200 Watt panels sounds a little off... Normally, 200 Watt panels are either 30 volt or 36 volts Vmp (there are other voltages too).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • jonr
    jonr Solar Expert Posts: 1,386 ✭✭✭✭
    #4
    Expanding on what others said, when your input voltage is higher than Vmp, that indicates that your load is less than the panel capacity and so energy is "left in the panels".    When the input voltage is about equal to Vmp, then your loads are >= panel capacity.

    A minor issue, but the MT50 is lying in that it claims 100% efficiency.

    I am available for custom hardware/firmware development

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