Can battery condition affect the PV output readings on MPPT controller?

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Brix
Brix Registered Users Posts: 3 ✭
edited September 2018 in Solar Beginners Corner #1
Hello,

I have fitted an off grid system on a cabin in mid Wales UK.
The three 80W panels are vertical facing just off south connected in parralel.
I have an Epever (EpSolar) Tracer MPPT controller.
Charging a 12V 110Ah Numax leisure battery (4 years old). 
I have had a constant load of 0.2A (toilet fan) connected to the MPPT controller.

I have been getting consistently paltry readings from the system. 0-0.2A at 14-21V (rarely 0.0 but happened to be when I was recording the video below).  I am very rarely there to take readings but the controller has recorded about 12kWh since April (about 4 months). The load is showing 6kWh for the same period.

This is a video of the MPPT readings and also shows the panels and siting: https://1drv.ms/v/s!Ao8QCjSb8RLPvlsnJIwV4U4j4CR5.

During a visit last week I left my phone on to charge overnight on a 2A USB socket. I think have left my screen turned on. In the morning the battery was discharged, reading 10 point something Amps, so presumably it was buggered. I replaced it with another battery (same age/model) from a PV system in a caravan. The PV reading on the controller leapt to about 7A - a reading I had not seen since similar readings on the first day of installation. It then soon settled down to the same pattern.

I think the max output I have seen from the caravan installation in a nearby location is 2A from a single 80W panel laid flat on the roof (not an MPPT controller). 

I guess my question is fairly simple - can the condition of the battery affect the PV output readings on the controller? I assume not. In which case, any suggestions?

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  • mcgivor
    mcgivor Solar Expert Posts: 3,854 ✭✭✭✭✭✭
    edited September 2018 #2
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    The controller needs a higher voltage input, the 80W panels need to be put in series for around 60V, a 12V nominal panel puts out around 20V, which is not enough to allow the MPPT tracking to work properly. Secondly if the battery has lost capacity it may demonstrate the symptoms explained, the video link didn't work for me, but if the voltage climbs rapidly from say 12V to 14.4 V, the battery is at end of life.
    Ivor 
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery with Battery Bodyguard BMS 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
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  • Brix
    Brix Registered Users Posts: 3 ✭
    #3
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    Oh dear. What a muppet! Thanks for the help.

    I have wired the panels in using 4mm cable. Will this still be ok? Run from panels to the controller is about 4m.
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  • mcgivor
    mcgivor Solar Expert Posts: 3,854 ✭✭✭✭✭✭
    #4
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    Yes 4mm is fine, the higher voltage would mean a smaller conductors could be used, but larger would be no problem. The best is to have about double the nominal voltage but since you have 3 in total series is the only option, should work fine, I use 90V to charge 24V nominal, mainly because of distance between array and controller.
    Ivor 
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery with Battery Bodyguard BMS 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
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  • littleharbor2
    littleharbor2 Solar Expert Posts: 2,044 ✭✭✭✭✭
    edited September 2018 #5
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    Your battery appears full from the readout on the controller. When full it will not take any, or very little, current. When you swapped batteries the new battery need a charge so was accepting all available current. Your vertical array would likely produce better in the winter,(on sunny days), than in summer. Beautiful countryside and quite the view you have there.

    2.1 Kw Suntech 175 mono, Classic 200, Trace SW 4024 ( 15 years old  but brand new out of sealed factory box Jan. 2015), Bogart Tri-metric,  460 Ah. 24 volt LiFePo4 battery bank. Plenty of Baja Sea of Cortez sunshine.

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  • Brix
    Brix Registered Users Posts: 3 ✭
    #6
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    littleharbor2 said:
    Your battery appears full from the readout on the controller. When full it will not take any, or very little, current. When you swapped batteries the new battery need a charge so was accepting all available current. Your vertical array would likely produce better in the winter,(on sunny days), than in summer. Beautiful countryside and quite the view you have there.
    Thanks. It is a beautiful spot. Quite the antidote to the inner city where I live!



    Re the readings, I have to admit I am not certain exactly what the actual readings represent:
    PV Volts/Amps : I assume this is what is available to battery and load form the array at the time, whether or not there is capacity to use or store it.
    Battery : V is state of charge
                   A is the total of input minus demand?(which sometimes reads negative - presumably if using power faster than charging?) 

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  • Estragon
    Estragon Registered Users Posts: 4,496 ✭✭✭✭✭
    #7
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    Volts is a condition or state. It's the electrical potential between two points.

    Amps is a flow, requiring both a source and a load.

    The meter can read potential PV voltage, but can't read potential current (amps) without an actual load. It might measure actual amps though, presumably by toggling a button?

    On the battery side, voltage can approximate state of charge provided there are no significant loads or charging sources.
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
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