Is there any reason to NOT over rate an MPPT

I'm running a 12 volt system and I've had some issues with the PWM CC I bought and I am now looking to replace it.

At this point in time I really only "need" a 20 amp CC but considering the possibility of future upgrades / expansion (not grid tie) is there any downside / reason to not get a 40 amp model up front?

I'm looking at Epever MPPT controllers and the difference between the 20, 30 and 40a versions is not so wide as to make not needing to upgrade the CC at a later date less expensive. 


Comments

  • BB.BB. Super Moderators, Administrators Posts: 30,637 admin
    Larger MPPT controllers tend to take a bit more power to operate... See if you can find an efficiency curve vs current... If you have a reasonably sized array (closer to 50% of controller capacity vs 10%), it should not be a big issue.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • jonrjonr Solar Expert Posts: 1,376 ✭✭✭✭
    A typical MPPT charge controller will be slightly more efficient at 30-50% of capacity than anything near 100%.

    I am available for custom hardware/firmware development

  • EstragonEstragon Registered Users Posts: 4,478 ✭✭✭✭✭
    ... and may run cooler under lighter load, generally a Good Thing for all things electronic.
    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
  • fratermusfratermus Registered Users Posts: 42 ✭✭
    Estragon said:
    ... and may run cooler under lighter load
    Isn't heat under light load more a function of PWM switching? 


    2017 Promaster 159" DIY camper
    570W mono / 220AH GC
  • fratermusfratermus Registered Users Posts: 42 ✭✭
    garynappi said:
    I'm looking at Epever MPPT controllers and the difference between the 20, 30 and 40a versions is not so wide

    Depending on the type of epever controller (A, B, whatever) the physical size differential can be surprising.  Check your available space against the actual size of the larger one to make sure it will fit where you want it to go.
    2017 Promaster 159" DIY camper
    570W mono / 220AH GC
  • mountainmanmountainman Registered Users Posts: 368 ✭✭
    The epever specs 12ma self consumption on all the an controllers.
    Blue ridge mts. Renogy pwm 4 100 watt and 2 190 evergreen on Epever mppt 30. 4 Gc 208 ah @12 volts 300 watt psw inverter. 2 kw genny. Iota 45.
  • mountainmanmountainman Registered Users Posts: 368 ✭✭
    edited November 2019 #8
    Agreed on most efficient at 50℅ vs 100℅. also the highest voltage array is less efficient.  this a 3210 an
    Blue ridge mts. Renogy pwm 4 100 watt and 2 190 evergreen on Epever mppt 30. 4 Gc 208 ah @12 volts 300 watt psw inverter. 2 kw genny. Iota 45.
  • boBboB Solar Expert Posts: 975 ✭✭✭✭
    edited November 2019 #9
    At least those Chinese MPPT controllers are cheap enough that you can buy an extra or two in case overloading one should harm it.

    What it will do when over PV'd is to run warmer because when it current limits its output to the battery, the input voltage will rise higher than normal.  But on cloudy days, you should benefit from the nameplate over-rating of the PV input.
  • mountainmanmountainman Registered Users Posts: 368 ✭✭
    I've been using a 3210 an for 2 years now. 
    On heavy  over cast days a 380 watt array 
    Mt 50 shows 7 watts 14 volts .5 amps. 
    On my 400 watt pwm on the same day I'm seeing~ 75 watts.
    In my opinion these controllers are not a good choice for over paneling for more out put on over cast days.
    When in full sun or light clouds seems to work fine. Slightly more power from 380 watts than 400 on pwm.
    Blue ridge mts. Renogy pwm 4 100 watt and 2 190 evergreen on Epever mppt 30. 4 Gc 208 ah @12 volts 300 watt psw inverter. 2 kw genny. Iota 45.
  • mcgivormcgivor Solar Expert Posts: 3,426 ✭✭✭✭✭
    I've been using a 3210 an for 2 years now. 
    On heavy  over cast days a 380 watt array 
    Mt 50 shows 7 watts 14 volts .5 amps. 
    On my 400 watt pwm on the same day I'm seeing~ 75 watts.
    In my opinion these controllers are not a good choice for over paneling for more out put on over cast days.
    When in full sun or light clouds seems to work fine. Slightly more power from 380 watts than 400 on pwm.
    You're chasing your tail, depending on temperature PWM may in fact produce more than MPPT, don't get caught up in minor discrepancies, you'll drive yourself crazy, each has its own set of advantages and disadvantages it is what it is.
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery bank 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah FLA 24V nominal 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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