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electrical:solar:charge_controller [2021/06/23 13:59]
frater_secessus [how to choose]
electrical:solar:charge_controller [2022/05/03 11:09] (current)
frater_secessus [how to choose] removed footnote, inlined the comment
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 Charge controllers are generally **rated by the amount of output they can provide**. This output is shared by charging circuits and [[#using_load_output|LOAD circuits]].  For example, a 20A controller might be using 18A for charging and have 2A available for LOAD. Charge controllers are generally **rated by the amount of output they can provide**. This output is shared by charging circuits and [[#using_load_output|LOAD circuits]].  For example, a 20A controller might be using 18A for charging and have 2A available for LOAD.
 Controllers operate based on [[electrical:solar:charge_controller_setpoints|factory- or user-defined setpoints]] (values) stored internally. Controllers operate based on [[electrical:solar:charge_controller_setpoints|factory- or user-defined setpoints]] (values) stored internally.
-===== types of charge controllers =====+===== specs ===== 
 + 
 +Regardless of type, controllers will have several specifications in common.  
 + 
 +  * **rating (or "size")** - this is usually the maximum output the controller can produce (charging + loads).((for technical reasons with PWM this will also be the *input* current limit)) 
 +  * **12v/24v/48v** - this refers to the nominal voltage of the battery bank it will be charging.  
 +  * **Maximum input voltage** - the highest voltage the controller should //ever// see from the solar array.((it is common to leave ~20% margin))  NOTE: a 50v input max does //not// mean a PWM controller can make efficient use of mismatched panel/battery voltages; that requires MPPT.  See [[#how_to_choose|how to choose]] below. 
 + 
 + 
 + 
 +===== Types of charge controllers =====
 [note from frater secessus: PWM vs. MPPT debates can get overheated in forums and comments. It's your money and your build so do it the way that meets your needs.] [note from frater secessus: PWM vs. MPPT debates can get overheated in forums and comments. It's your money and your build so do it the way that meets your needs.]
 +
 +=== 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 ==== ==== 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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 Note that there are some simple PWM controllers like Morningstar's [[https://amzn.to/3lvk0Ze|SunGuard]] that [[electrical:12v:eternal_absorption|run at a single voltage]]. Note that there are some simple PWM controllers like Morningstar's [[https://amzn.to/3lvk0Ze|SunGuard]] that [[electrical:12v:eternal_absorption|run at a single voltage]].
 +
 +[[https://diysolarforum.com/threads/why-is-mppt-better-than-pwm.24892/post-295861|For technical reasons]] PWM can deliver more current than the panels' Imp, even nearing Isc.
 ==== MPPT ==== ==== MPPT ====
 [[http://amzn.to/2iD3WKf|{{ https://images-na.ssl-images-amazon.com/images/I/51bi9IjcsRL._AC_US160_.jpg}}]] [[http://amzn.to/2iD3WKf|{{ https://images-na.ssl-images-amazon.com/images/I/51bi9IjcsRL._AC_US160_.jpg}}]]
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       * when a typical 100w panel((Iop = 5.6A)) is run at 12.2v in lab conditions it puts out **~68.32W**. The same panel run at Vmp (~17v) would put out **100W**.  **MPPT is capturing more power than the PWM when the battery needs it most**.((there are minor inefficiencies not considered here))       * when a typical 100w panel((Iop = 5.6A)) is run at 12.2v in lab conditions it puts out **~68.32W**. The same panel run at Vmp (~17v) would put out **100W**.  **MPPT is capturing more power than the PWM when the battery needs it most**.((there are minor inefficiencies not considered here))
   * during times of greatest PV efficiency((i.e. highest voltage)) (clear, cold weather)   * during times of greatest PV efficiency((i.e. highest voltage)) (clear, cold weather)
-  * during times of low irradience (low light levels due to low angle or overcast conditions)((this is a function of higher input voltages))((https://www.victronenergy.com/upload/documents/White-paper-Which-solar-charge-controller-PWM-or-MPPT.pdf Section 7.3))+  * during times of low irradience (low light levels due to low angle or overcast conditions)((this is a function of higher input voltages)),((https://www.victronenergy.com/upload/documents/White-paper-Which-solar-charge-controller-PWM-or-MPPT.pdf Section 7.3)) 
 +   
 There are some considerations when [[electrical:solar:mppt design|designing a system around an MPPT controller]]. There are some considerations when [[electrical:solar:mppt design|designing a system around an MPPT controller]].
 ==== shunt  ==== ==== shunt  ====
 +
 +see article below
 +
 +
 +==== single-stage chargers ====
  
 [[http://amzn.to/2yQppTX|{{ https://images-na.ssl-images-amazon.com/images/I/41Gwyw0BT5L._AC_US160_.jpg}}]] [[http://amzn.to/2yQppTX|{{ https://images-na.ssl-images-amazon.com/images/I/41Gwyw0BT5L._AC_US160_.jpg}}]]
-In this usage, //shunt controllers// are single-stage chargers that hold the bank at a [[electrical:solar:charge_controller_setpoints|setpoint]] (Vdisconnect) as long as sufficient solar harvest is present.  When the setpoint voltage is achieved the controller is turned off for some amount of time.((In a hydro or windpower scenario the power cannot be turned off and is diverted (shunted) instead to a diversion load like water heating, water pumping, etc.))   +Single-stage chargers hold the bank at a [[electrical:solar:charge_controller_setpoints|setpoint]] (Vdisconnect)((whether generally or exactly)) as long as sufficient solar harvest is present.  When the setpoint voltage is achieved the controller current is turned off for some amount of time.((In a hydro or windpower scenario the power cannot be turned off and is diverted (shunted) instead to a diversion load like water heating, water pumping, etc.)) There are several different ways of turning off the current: 
 + 
 +  * PWM - open circuit the panels very rapidly (tens-to-thousands times a second)and for varying lengths of time to hold the voltage setpoint more precisely.  Same as PWM controllers above, but in this market range the modulation tends to be cruder/slower and there is only one charging voltage setpoint. 
 +  * shunt - shorts the panels ON/OFF (charge-and-stop, less common)  
 +  * series - open circuits the panels ON/OFF (charge-and-stop, less common)
  
 Simple versions use simple electronics((as with [[https://www.flexcharge.com|Flexcharge]])) or relays to turn charging on until Vdisconnect is reached, at which point charging is turned off off. If/when voltage falls to some lower voltage (Vreconnect) charging begins again.  This is sometimes called [[electrical:12v:charging#charge-and-stop|charge and stop charging]] or on/off charging.  Voltage tends to wander a bit as the charging stops and starts.  They are often used where extreme simplicity/robustness is required, or where more complex electronics might cause electrical interference.((as in a ham shack)) Simple versions use simple electronics((as with [[https://www.flexcharge.com|Flexcharge]])) or relays to turn charging on until Vdisconnect is reached, at which point charging is turned off off. If/when voltage falls to some lower voltage (Vreconnect) charging begins again.  This is sometimes called [[electrical:12v:charging#charge-and-stop|charge and stop charging]] or on/off charging.  Voltage tends to wander a bit as the charging stops and starts.  They are often used where extreme simplicity/robustness is required, or where more complex electronics might cause electrical interference.((as in a ham shack))
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 > If your charge controller only holds [absorption] voltage for an hour or two, that is likely not enough time. As long as [there is a load] and you cycle the battery daily, you could set float voltage to 14.8v [to match absorption] without worry. Only when you stop cycling the battery do you need to return float voltage to more regular 13.2v levels. Premature application of float voltage by automatic charging sources is a battery killer.((http://www.cheaprvliving.com/forums/Thread-Solar-or-Battery-Problem?pid=229883#pid229883)) > If your charge controller only holds [absorption] voltage for an hour or two, that is likely not enough time. As long as [there is a load] and you cycle the battery daily, you could set float voltage to 14.8v [to match absorption] without worry. Only when you stop cycling the battery do you need to return float voltage to more regular 13.2v levels. Premature application of float voltage by automatic charging sources is a battery killer.((http://www.cheaprvliving.com/forums/Thread-Solar-or-Battery-Problem?pid=229883#pid229883))
 +
 +Also see [[https://goughlui.com/2020/06/05/teardown-tested-generic-kw12x0-w88-solar-charge-controller-10-30a-versions/|this comprehensive teardown]] that assesses:
 +
 +> ....a rather inexpensive piece of equipment but it doesn’t do a terrible job of being a basic solar charge controller. On the whole, it behaves as one may expect – protecting the battery from excessive voltage and overdischarge, with an integrated dusk timer function and USB outputs...what do you expect for $10-20? Something that works is already a big surprise to me.
 +
 +==== USB converters ====
 +[[https://amzn.to/3msdCUU|{{ https://m.media-amazon.com/images/I/71EmsM+loWL._AC_SY200_.jpg?50}}]] 
 +These aren't controllers in the normal sense, but there are [[https://amzn.to/3msdCUU|modules]] that connect to your panel's MC4 connectors and output USB power.  
 +
 +If you only need 5v USB power up to 2.5A per port this may be a workable solution. 
  
 ==== DDCCC ==== ==== DDCCC ====
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 If more power is needed (and there is physical space) additional PV can be added to match the charging output of an MPPT charger, often at a lower cost.  [There are no prizes for fanciest or most expensive charge controller!  Do what is best for you -- frater secessus] If more power is needed (and there is physical space) additional PV can be added to match the charging output of an MPPT charger, often at a lower cost.  [There are no prizes for fanciest or most expensive charge controller!  Do what is best for you -- frater secessus]
  
-PWM's limitations are reduced when [[electrical:12v:alt_and_solar|other forms of charging are present to help]], and when battery voltage is relatively high: +There are also edge cases where //PWM can actually make more power than MPPT//.  An example of this might be low-Vmp poly [[electrical:solar:panels|panels]] during Absorption stage in very hot weather, due to MPPT DC-DC conversion losses and [[electrical:solar:output#panel_temperature|temperature derating]].
- +
-There are also edge cases((low altitude, high temperature, Absorption)) where PWM can actually make more power than MPPT.  An example of this might be low-Vmp poly [[electrical:solar:panels|panels]] during Absorption stage in very hot weather, due to MPPT DC-DC conversion losses and [[electrical:solar:output#panel_temperature|temperature derating]].+
  
 **MPPT is effectively required** when: **MPPT is effectively required** when:
-  * using panels with nominal voltages higher than 12v ((more presciselywhen panel nominal voltage exceeds house bank nominal voltage))+  * 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
   * daytime loads are hampered by [[electrical:solar:pwm_tweaking|PWM Vbatt hobbling]]   * daytime loads are hampered by [[electrical:solar:pwm_tweaking|PWM Vbatt hobbling]]
   * [[#overpaneling|overpaneling]]   * [[#overpaneling|overpaneling]]
   * making [[electrical:converter#diy_converters|DIY converters]]   * making [[electrical:converter#diy_converters|DIY converters]]
-We say "effectively required" because one //can// use 24v panels with PWM and 12v banks -- it just doesn't work very well.  The 24v panels will be run at 12v voltages, yielding about half the power you would get with MPPT. + 
  
 Further reading:   Further reading:  
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   * the existing PWM system is not providing enough output   * the existing PWM system is not providing enough output
-  * using monocrystalline panels, as the higher Vmp and lower Imp further reduces PWM output.+  * nominal 12v panels have a relatively high Vmp (>=18v) for [[https://www.reddit.com/r/vandwellers/comments/bmlosu/is_vandwelling_a_frugal_lifestyle/emz5lsf/?context=1|reasons discussed here]].
   * battery banks are cycled deeply on a regular basis so more time is spent at low Vbatt where PWM struggles.   * battery banks are cycled deeply on a regular basis so more time is spent at low Vbatt where PWM struggles.
 +  * with deeply-discharged banks of low internal resistance (AGM and especially lithium).  Their voltage will take more time to rise from deeply-cycled levels.((https://marinehowto.com/mppt-vs-pwm-solar-controllers/)) 
   * charging is by solar //only//;  no [[electrical:generator|generator]], [[electrical:shore_power|shore power]], or alternator charging to help.   * charging is by solar //only//;  no [[electrical:generator|generator]], [[electrical:shore_power|shore power]], or alternator charging to help.
-  * nominal 12v panels have a relatively high Vmp (>=18v) for [[https://www.reddit.com/r/vandwellers/comments/bmlosu/is_vandwelling_a_frugal_lifestyle/emz5lsf/?context=1|reasons discussed here]]. 
-  * if multiple panels will be used in areas of [[electrical:solar:shading|partial shade]] 
   * if temperatures are very low (rising Vmp means increasing output which PWM could not capture)   * if temperatures are very low (rising Vmp means increasing output which PWM could not capture)
   * the increase in cost is not an undue burden   * the increase in cost is not an undue burden
-  * with deeply-discharged banks of low internal resistance (AGM and especially lithium).  They will remain at lower voltages longer while accepting current, hamstringing PWM.((https://marinehowto.com/mppt-vs-pwm-solar-controllers/))  
  
 **Shunt controllers** are extremely inexpensive, making them useful for even very small systems, test configurations, and backups.  **Shunt controllers** are extremely inexpensive, making them useful for even very small systems, test configurations, and backups. 
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 As with [[electrical:inverter|inverters]], sizing the controller correctly will help system efficiency and save money.  An oversized CC will have unnecessarily high parasitic drains as it powers itself and will cost more.  An undersized CC will not be able to put all the rated solar wattage to use and will leave no room for expansion. As with [[electrical:inverter|inverters]], sizing the controller correctly will help system efficiency and save money.  An oversized CC will have unnecessarily high parasitic drains as it powers itself and will cost more.  An undersized CC will not be able to put all the rated solar wattage to use and will leave no room for expansion.
 For PWM controllers, the formula is something like (panel wattage / 13) * (1.2 oversize for safety) = charge controller amps.((https://www.altestore.com/howto/sizing-pwm-solar-charge-controllers-a91/))  For PWM controllers, the formula is something like (panel wattage / 13) * (1.2 oversize for safety) = charge controller amps.((https://www.altestore.com/howto/sizing-pwm-solar-charge-controllers-a91/)) 
-MPPT controllers have more leeway in sizing since they can control the output of the panels independently of battery voltage.  +MPPT controllers have more leeway in sizing since they can [[electrical:solar:overpaneling|control the output of the panels]] independently of battery voltage.  
 See also [[electrical:solar:sizing|Sizing a Solar Installation]] See also [[electrical:solar:sizing|Sizing a Solar Installation]]
 ===== overpaneling ===== ===== overpaneling =====
 this section [[electrical:solar:overpaneling|has been moved]]. this section [[electrical:solar:overpaneling|has been moved]].
 ===== Using LOAD output ===== ===== Using LOAD output =====
-It is common for charge controllers to have a LOAD output for powering (or switching) loads.  One benefit to doing this is you can define a [[electrical:12v:lvd|Low Voltage Disconnect]] (LVD) setpoint and Low Voltage Reconnect to protect the battery from excessive discharge. + 
-Not all types of loads should be run from these terminals, though.  Morningstar says:+It is common for charge controllers to have a LOAD output for powering (or switching) loads.  A common-and-understandable misperception is that it is there to run your loads.  Kinda.   
 + 
 + 
 +==== historical use ==== 
 + 
 +LOAD terminals were originally used to control nighttime lighting, like pathway or garden lights.  These are relatively small, resistive loads.  Power to the LOAD terminal could be associated with sun (or lack of sun) and/or battery voltage.  
 + 
 +==== present use ==== 
 + 
 +In practice the LOAD terminals typically are either ignored((some well-respected controllers don't have them anymore)) or used as [[electrical:12v:lvd|low voltage disconnects]] power relays (see below).   
 + 
 +One benefit to doing this is you can define a [[electrical:12v:lvd|Low Voltage Disconnect]] (LVD) setpoint and Low Voltage Reconnect to protect the battery from excessive discharge: 
 + 
 +==== why loads aren't powered from LOAD terminals ==== 
 + 
 + 
 +> The load outputs take power from the battery terminals.... the only advantage in using the load terminals is displayed info and the ability to disconnect the load at programmable voltage levels. -- mikefitz((https://diysolarforum.com/threads/epever-solar-charge-controller-false-measurements-on-the-load.23995/post-283823)) 
 + 
 +Some loads are inappropriate for the LOAD output.  Morningstar says: 
 >  Heavily inductive or capacitive loads such as **pumps, motors, compressors, and  >  Heavily inductive or capacitive loads such as **pumps, motors, compressors, and 
 inverters** should not be wired to the controller’s Load terminals. In addition, loads exceeding the Load Current Rating of the controller should not be connected to the controller’s Load terminals.((http://support.morningstarcorp.com/wp-content/uploads/2014/07/ALL.DIG_.Load_Control_Using_A_Relay.01.EN_.pdf)) inverters** should not be wired to the controller’s Load terminals. In addition, loads exceeding the Load Current Rating of the controller should not be connected to the controller’s Load terminals.((http://support.morningstarcorp.com/wp-content/uploads/2014/07/ALL.DIG_.Load_Control_Using_A_Relay.01.EN_.pdf))
 +
 elsewhere they say: elsewhere they say:
 +
 >  Inductive loads can generate large voltage spikes that may damage the controller’s lightning protection devices.((http://www.morningstarcorp.com/wp-content/uploads/2014/02/TS.IOM_.Operators_Manual.04.EN_1.pdf))  >  Inductive loads can generate large voltage spikes that may damage the controller’s lightning protection devices.((http://www.morningstarcorp.com/wp-content/uploads/2014/02/TS.IOM_.Operators_Manual.04.EN_1.pdf)) 
 although an exception is made for the SunSaver MPPT which "Handles inductive loads without problems."((http://support.morningstarcorp.com/wp-content/uploads/2014/07/SunSaverMPPT-FeaturesBenefits.pdf)) although an exception is made for the SunSaver MPPT which "Handles inductive loads without problems."((http://support.morningstarcorp.com/wp-content/uploads/2014/07/SunSaverMPPT-FeaturesBenefits.pdf))
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 Note:  in wind and hydro power applications the output can be sequenced so that LOAD is activated only when batteries are fully charged.  This is called a "dump load" because those power sources need to be able to "dump" excess current to prevent damage to themselves.  Dump loads are not necessary in solar because panels can be open- or short-circuited without damage. Note:  in wind and hydro power applications the output can be sequenced so that LOAD is activated only when batteries are fully charged.  This is called a "dump load" because those power sources need to be able to "dump" excess current to prevent damage to themselves.  Dump loads are not necessary in solar because panels can be open- or short-circuited without damage.
 +
 +
 ===== positive ground controllers ===== ===== positive ground controllers =====
 Some controllers are labeled or described as "positive ground", often by their competitors.  The term is incorrect and misleading: Some controllers are labeled or described as "positive ground", often by their competitors.  The term is incorrect and misleading:
electrical/solar/charge_controller.1624471194.txt.gz · Last modified: 2021/06/23 13:59 by frater_secessus