====== Series and Parallel solar arrays ======

===== TL;DR =====

  * With [[electrical:solar:charge_controller#mppt|MPPT]] solar charge controllers and 12v house battery bank there is often //little practical difference between parallel and series solar arrays//.  
  * [[electrical:solar:charge_controller#pwm|PWM controllers]] run arrays of the same nominal voltage as their battery bank:  12v and 12v, 24v and 24v.
  * //generally speaking//, parallel panels will perform better in [[electrical:solar:shading|partial shade]] than series. [but don't shade your panels in the first place -- secessus]
  * as with other [[electrical:12v:parallel_serial|series/parallel arrangements]], series increases voltage and parallel increases current.
  * series arrays can reduce capital costs in some circumstances
  * series/parallel arrangements are described with ''xPxS'' nomenclature:
    * 2 panels in parallel would be 2P1S
    * 2 panels in series would be 1P2S
    * 4 panels in series-parallel would be 2P2S


===== Series =====

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 [[electrical:solar:shading#exceptionhigh_voltage_strings_mppt|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 Vmp**((https://www.youtube.com/watch?v=JfzT8u205co))
    * slightly better than parallel when **mixing PV of different Imp //and// Vmp**((https://www.youtube.com/watch?v=ZAKTMSEHfk8))
    * 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




===== Parallel =====


  * PRO
    * less impacted by partial shade((http://ccsenet.org/journal/index.php/mas/article/viewFile/3937/3464)) when using PWM controllers
    * more efficient than series when mixing PV of **same Vmp but different Imp**((https://www.youtube.com/watch?v=P3YtBrymJdA))
    * 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



===== Series-Parallel =====

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 ([[electrical:12v:parallel_serial|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. 

===== further reading =====

  * [[https://www.explorist.life/solar-panels-series-vs-parallel/|Solar Panels – Series vs Parallel]] by Explorist Life
  * [[https://www.youtube.com/watch?v=1s2gsKWqyjM|How To Wire Solar Panels In Series vs Parallel -- For Beginners]]
  * [[https://www.cruisersforum.com/forums/f14/shading-serial-vs-parallel-this-time-with-data-284237.html|testing series vs parallel in a marine environment]]