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electrical:solar:charge_controller

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electrical:solar:charge_controller [2022/08/09 14:05]
frater_secessus [further reading] 		electrical:solar:charge_controller [2022/10/12 13:15]
frater_secessus [how to choose]
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 === The quick and dirty ===  === The quick and dirty === 
  
-**PWM** is a lot cheaper, but less gives less power (50-60% of panel input can be used). **MPPT** is more expensive, but gives more power (80-90% of panel input can be used)+**PWM** is much less expensive, and typically makes less power over the course of the day. Panel voltage and battery bank voltage need to be matched.  
 + 
 +**MPPT** is more expensive and but typically makes more power, especially when battery voltage is low.   Panel voltage and battery bank voltage can diverge.  
 + 
 +The more power / less power dynamic is highly dependent on the setup and use case; there are no definite answers about which is right for you.  For example, there are edge scenarios where PWM can make more power than MPPT.((like high ambient temps + low Vmp panels)) 
 + 
 ==== PWM ==== ==== PWM ====
 [[http://amzn.to/2hcZaj2|{{ https://images-na.ssl-images-amazon.com/images/I/41pwJOriZHL._AC_US160_.jpg}}]]**PWM** (pulse width modulation) controllers charge by connecting panels to battery until a given voltage setpoint is reached.  When the desired setpoint is reached the controller switches current on/off to the battery in very fast cycles and in such a duration needed to keep voltage from rising.  This time slicing power delivery is called is pulse width modulation, or PWM.  Some heat will be generated by the switching. Counterintuitively, the PWM may be cooler the touch when it is running full open because there is no switching going on to limit voltage. [[http://amzn.to/2hcZaj2|{{ https://images-na.ssl-images-amazon.com/images/I/41pwJOriZHL._AC_US160_.jpg}}]]**PWM** (pulse width modulation) controllers charge by connecting panels to battery until a given voltage setpoint is reached.  When the desired setpoint is reached the controller switches current on/off to the battery in very fast cycles and in such a duration needed to keep voltage from rising.  This time slicing power delivery is called is pulse width modulation, or PWM.  Some heat will be generated by the switching. Counterintuitively, the PWM may be cooler the touch when it is running full open because there is no switching going on to limit voltage.
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 high for system needs((particularly with higher than nominal 12v panels )) the controller performs a DC-DC conversion to bring the voltage down to a directly usable level.  Because **current through a conductor is directly proportional to voltage**((https://en.wikipedia.org/wiki/Ohm%27s_law)) this downconversion effectively turns excess voltage into increased amps.(minus conversion losses).   high for system needs((particularly with higher than nominal 12v panels )) the controller performs a DC-DC conversion to bring the voltage down to a directly usable level.  Because **current through a conductor is directly proportional to voltage**((https://en.wikipedia.org/wiki/Ohm%27s_law)) this downconversion effectively turns excess voltage into increased amps.(minus conversion losses).  
  
-This ability to decouple panel and bank voltage can result in 10%-30% more power harvested from 12v nominal panels than with a PWM controller.  Marketers like to call this "boost" or "gains" but it really just full capture of whatever power the panel[s] can provide under given conditions.+This ability to decouple panel and bank voltage can result in 10%-30% more power harvested from 12v nominal panels than with a PWM controller, depending on conditions.  //Average// daily production with MPPT is typically ~+15%((https://www.redalyc.org/journal/849/84959429001/html/)), which may or may not justify the added cost on its own.   
  
 === "boost" effect === === "boost" effect ===
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 **MPPT is effectively required** when: **MPPT is effectively required** when:
 +  * when one needs to squeeze every watt out of the panel
   * using panels with nominal voltages higher than the battery bank voltage, like 24v panels with a 12v bank.   To be fair, [[http://mouse.mousetrap.net/blog/2021-07-09-solar-back-online-.html#pwm-spare-saved-my-bacon|one really can use higher-voltage panels with PWM and 12v banks]] -- they just end up running at about half power.       * using panels with nominal voltages higher than the battery bank voltage, like 24v panels with a 12v bank.   To be fair, [[http://mouse.mousetrap.net/blog/2021-07-09-solar-back-online-.html#pwm-spare-saved-my-bacon|one really can use higher-voltage panels with PWM and 12v banks]] -- they just end up running at about half power.    
   * space available for panels is limited, as on a sailboat or small vehicle   * space available for panels is limited, as on a sailboat or small vehicle
electrical/solar/charge_controller.txt · Last modified: 2024/04/16 20:28 by frater_secessus

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