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Series and Parallel solar arrays

Generally speaking, parallel arrays of nominal 12v panels are used with pwm charge controllers and serial arrays or higher nominal voltage panels are used with MPPT controllers.


Series arrays are used to generate higher voltages to feed the controller.

  • PRO
    • higher PV voltage can run in relatively thinner wires to the charge controller
    • serial connections can provide some charging in low light situations where lower voltage parallel or single-panel connections might not. Imagine two nominal 12v panels running at 11v at sunrise; the series arrangement might yield ~22v (battery charging) instead of 11v (voltage too low to charge battery). Note that power harvestable at those times may be quite low.
    • higher-voltage serial configurations with MPPT controllers may provide more power under partial shading
    • higher voltages work well with MPPT controllers
    • higher voltages can charge higher voltage battery systems like 24v.
    • more efficient than parallel when mixing PV of same Imp but different Vmp1)
    • slightly better than parallel when mixing PV of different Imp and Vmp2)
    • higher voltages can help overcome minimum delta requirements to get the MPPT algo running (Victron controllers, for example, require +5v to start and +1v to maintain MPPT).
  • CON
    • series arrays can generate quite high operating voltages. Be sure your controller can handle the VoC with edge effect.
    • requires MPPT charger to get full use of high-voltage arrays under normal conditions.
    • thin film panels are generally not recommended for use in serial arrays
    • short serial strings are more susceptible to partial shading losses than parallel


  • PRO
    • less impacted by partial shade3) when using PWM controllers
    • more efficient than series when mixing PV of same Vmp but different Imp4)
    • can use charge controllers with lower max voltage input rating
    • can use simpler, less expensive PWM charge controllers with nominal 12v panels without losing much efficiency
  • CON
    • may not provide sufficient voltage to charge battery during very bad conditions (insolation < 20%)
    • may not provide sufficient voltage to charge higher voltage (20 or 24v) battery banks


Consider this scenario:

  • 4 panels
    • 150w
    • Vmp == 19v
    • Voc == 22.8
    • Imp == 7.9A
  • MPPT controller with 60v maximum input voltage

A fully-series configuration (1p4s) would have a Voc of 91.2v, greatly exceeding the controller's input spec of 60v, and it's common to want to have 20% voltage headroom above Voc.

A fully-parallel configuration (4p1s) would require 3x 2-into-1 MC4 adapters or 1x 4-into-1 adapter. The wiring from the array would need to carry 30A+ to the controller, necessitating heavier wiring that would cost more and might not even fit the controller terminals. It might be unable to charge at all under extreme low-light conditions.

A compromise might be series-parallel array (2p2s) with 45.6Voc and ~16A. This would require 1x 2-into-1 MC4 adapter to combine the two serial strings. Voltage is low enough for the controller, but high enough to allow low-light charging and the use of lighter wiring.

electrical/solar/series_vs_parallel.txt · Last modified: 2021/06/06 15:28 by frater_secessus