Controller recommendation

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cptdondo
cptdondo Solar Expert Posts: 103 ✭✭✭
edited July 2020 in Solar Beginners Corner #1
I have room for 2 of these panels:

  • Vmp: 34.2 Volts
  • Voc: 40.3 Volts
  • Imp: 9.37 Amps
  • Isc: 10.22 Amps
I am looking for a controller recommendation.  I guess my question is if I need to charge 12V batteries, am I looking for a 20A controller or a 60A controller?  (Assuming that the max charge into 12V batteries would be 60A).

I don’t need the biggest and best; just a simple one (or two).

Would this be a good fit?

https://www.solar-electric.com/lib/wind-sun/TSdatasheet.pdf

I don’t mind it being PWM.

If not, a brand and model would be awesome!
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  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    #2
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    640W @ 13V is a 49A controller, 60A is a common value in controllers.

    With those panels, and a MPPT controller, you get 49A, with a PWM controller you get 18A, into a 12V battery. 

    Why are you not looking at a 24V system, what are your loads you need to power ?
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

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  • cptdondo
    cptdondo Solar Expert Posts: 103 ✭✭✭
    #3
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    The existing system is 12V, so I am limited.  I am trying to replace an existing undersized 150W panel and controller.

    So would this be a better choice?

    https://www.solar-electric.com/outback-power-flexmax-fm60-150-mppt-charge-controller.html


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  • Photowhit
    Photowhit Solar Expert Posts: 6,003 ✭✭✭✭✭
    #4
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    cptdondo said:
    The existing system is 12V, so I am limited.  I am trying to replace an existing undersized 150W panel and controller.
    So would this be a better choice?
    https://www.solar-electric.com/outback-power-flexmax-fm60-150-mppt-charge-controller.html
    I think that's the best bang for the buck, in a quality controller.
    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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  • Solarguy1
    Solarguy1 Registered Users Posts: 9 ✭✭
    #5
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    mike95490 said:
    640W @ 13V is a 49A controller, 60A is a common value in controllers.

    With those panels, and a MPPT controller, you get 49A, with a PWM controller you get 18A, into a 12V battery. 


    Mike, I'm confused about this. Could you educate me on this, please? I'm trying to learn...

    Wouldn't his 2 panels put out only 9 amps if connected in series, or approximately 18 amps if wired in parallel?

    Where does the 49 amps come from?

    Thanks!
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,443 admin
    #6
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    This is the issue of "matching" your source power (solar panels) with the thing you are trying to charge/supply power too--In this case a 12 volt battery bank.

    Everyone is pretty understanding of how a battery performs... More or less, a 12 volt battery holds 12 volts whether charging or discharging (a first approximation, normal operation for a lead acid battery is 10.5 volts "dead" to 14.8 volts being charged--And around 12.0 to 12.7 volts fully charged).

    A solar panel is a "current source"... More or less, your 34.2 volt panel will output 9.37 amps--No matter if the load is a "dead short" or a 12 or 24 volt battery. Above ~34.2 volts, the output current ramps down, eventually to zero amps at 40.3 volts (Voltage open circuit Voc). (of course, there are other 2nd order effects, temperature, internal resistance, and the amount of sun light hitting the panel all affect output current and voltage).

    So, how does that "affect your design choices"... A PWM controller (Pulse Width Modulation) is really just an On/Off switch (controlled by a computer). If you have full noon-time sun, and the output current is 9.37 amps, the power into the battery bank is:
    • Power = Voltage * Current
    • Power Dead Short = 0 volts * 9.37 amps = 0 Watts
    • Power into 12 volt battery = 12 volts * 9.37 amps = 112 Watts
    • Power into 24 volt battery = 24 volts * 9.37 amps = 225 Watts
    • Power into "34.2 volt battery" = 34.2 volts * 9.37 amps = 320 Watts (Vmp = Voltage maximum power)
    • Power into "40.3 volt battery" = 40.2 volts * 0 amps = 0 Watts
    That is the "issue" of needing to match the proper solar panel Vmp voltage to the battery bank voltage. The typical 12 volt battery on a PWM controller should be around Vmp=17.5 to 18.x volts for "optimum" operation.

    An MPPT charge controller is sort of like the automatic transmission on a car (or the DC equivalent of a variable transformer)--It matches the IV (current voltage) curve of the solar array to that of the battery bank.

    Power = Voltage * Current
    34.2 volts * 9.37 amps from solar panel = 320 Watts = 14.75 volts battery charging * 21.7 Amps into battery bank

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,443 admin
    edited December 2020 #7
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    I should add the "=" sign is the "MPPT controller" Power in = Power out (through the magic of a digital switching power supply, the guts of the MPPT controller).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    #8
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    PWM controllers : Amps in = Amps out     18A in, 18A out
    MPPT controllers :  Watts in = Watts out    Watts are Volts x Amps    12v x 2A = 24Watts
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

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