Solar Panels more watt?

rmathersrmathers Registered Users Posts: 3
Can I go from 100 watt (2) panels to 200 watt (2) on a 40 amp controller 12 volt battery? :*


  • 706jim706jim Solar Expert Posts: 344 ✭✭✭
    Island cottage solar system with 2400 watts of panels, 1kw facing southeast 1kw facing southwest 400watt ancient Arco's facing south.Trace DR1524 MSW inverter, Outback Flexmax 80 MPPT charge controller 8 Trojan L16's. Insignia 11.5 cubic foot electric fridge. My 27th year.
  • mike95490mike95490 Solar Expert Posts: 8,875 ✭✭✭✭✭
    100w @ 12 v = 8.3A,  so 400w would only be 33A, so it would work.  What's the Vmp voltage on the 200w panels ?  if it's over 19V, you will not see the full 200w unless you use a MPPT controller
    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

    gen: ,

  • InCogKneeToeInCogKneeToe Registered Users Posts: 43 ✭✭
    My 100w 12v Polycrystalline (Blueish coloured)  panels produce 5.8A each. Coleman Branded Sunforce. Coleman Branded Sunforce 30A PWM Controller states Max 450w. It's never produced over 21As @ the Controller, using 4 Panels.

    So going to a 40A Controller PWM (as I have) I plan adding 2 more panels to the array totaling [email protected]
  • BB.BB. Super Moderators, Administrators Posts: 30,740 admin
    Details do matter with solar... There are PWM (Pulse Width Modulation) inexpensive solar charge controllers, and there are MPPT (Maximum Power Point Tracking) more expensive controllers (there is a third type--PWM controller fraudulently labeled as MPPT).

    PWM controllers typically have a solar array with Vmp~17.5 volt panels. Their maximum current is 4x Imp of the panel, or roughly (for example, a 600 Watt array on a PWM controller):
    • 600 Watt of panels (4x parallel connected) / 17.5 volts Vmp = 34.3 amps Imp array
    So that array would work fine on your 40 Amp PWM solar charge controller charging a 12 volt battery.

    If you have a MPPT type solar charge controller (typically more expensive than PWM)--The math is different, but MPPT controllers can "manage" their output current to rated current safely/reliably--So it is possible to "over-panel" an MPPT controller and have things work quite nicely. But the "math" (and array configuration) is different from PWM.

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • InCogKneeToeInCogKneeToe Registered Users Posts: 43 ✭✭
    edited July 30 #6
    Sorry, it wasn't my question. I just replied with what I know that works.

    I know that 400watts 12v can safely go to a 30A PWM Controller (450w actually in the Controllers Manual).

    I know that Harvest @ the Controller with 400w 12v, is only 20A with wiring losses(2 runs of 12AWG wire, 25 and 30').

    So I feel safe adding 2 more panels (100w each) to my 40A Controller totaling 600 watts, 12v PWM Controller.

    So the answer to the Original Posters question is YES, 200w 12v to a 40A Controller is safe. With room to expand. PWM or MPPT Controller. Poly or Mono 12v Panels
  • mountainmanmountainman Registered Users Posts: 385 ✭✭
    edited July 31 #7
    My hqst 30 amp pwm controller stated 450 watts @12 volts. 
    With 4 100 watt 5.3 imp panels on a cloudy morning and ~60 soc battery 40f temps.
    Sun came out midday I was seeing 26 amps.
    6.5 each from 5.3 imp  x6 =39 amps.
    So imo your taking a chance with 6  5.8 amp panels on a 40 amp pwm controller.
    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.
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