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electrical:solar:charge_controller [2022/08/09 14:05]
frater_secessus [low side switching] solar4rvs article
electrical:solar:charge_controller [2024/02/16 23:32] (current)
frater_secessus [how to choose] added video
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 [[lifestyle:words_of_wisdom|Words of wisdom]]:  //"Any Solar is better than no solar, but having too much solar is difficult. The best solar systems are those which can keep the batteries the happiest.  Happy batteries are those which are recharged quickly after depletion."//((http://www.cheaprvliving.com/forums/Thread-Should-I?pid=88971#pid88971)) - SternWake [[lifestyle:words_of_wisdom|Words of wisdom]]:  //"Any Solar is better than no solar, but having too much solar is difficult. The best solar systems are those which can keep the batteries the happiest.  Happy batteries are those which are recharged quickly after depletion."//((http://www.cheaprvliving.com/forums/Thread-Should-I?pid=88971#pid88971)) - SternWake
 ====== Solar charge controllers ====== ====== Solar charge controllers ======
 +
 +===== TLDR =====
 +
 +  * solar panels -> solar charge controller (SCC) -> battery bank
 +  * the SCC's main job is preventing //battery overcharge//
 +  * The two main types of SCC are PWM and MPPT
 +    * PWM - Cheaper, less efficient
 +    * MPPT - More expensive, but more efficient
 +  * SCC LOAD outputs are vestigial features but may be useful for triggering certain loads
 +
 +
 +[[opinion:frater_secessus:pareto|about this summary]]
 +
 +
 +==== overview ====
 +
 +
 +
 A solar charge controller (CC) regulates the [[electrical:12v:charging|charging]] of a [[electrical:12v:deep cycle battery|battery bank]] from the [[electrical:solar:panels|solar panels]]. A solar charge controller (CC) regulates the [[electrical:12v:charging|charging]] of a [[electrical:12v:deep cycle battery|battery bank]] from the [[electrical:solar:panels|solar panels]].
 Counterintuitively, the primary job of the charge controller (CC) is to keep the batteries from being //over//charged.  Solar panels run at higher voltages than batteries, often at voltages high enough to damage the batteries.  The CC provides the correct amount of power the battery needs at the correct time;  this is called [[electrical:12v:charging|smart or three stage charging]]. Counterintuitively, the primary job of the charge controller (CC) is to keep the batteries from being //over//charged.  Solar panels run at higher voltages than batteries, often at voltages high enough to damage the batteries.  The CC provides the correct amount of power the battery needs at the correct time;  this is called [[electrical:12v:charging|smart or three stage charging]].
 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.
 +
 +Cautionary example:  [[https://www.youtube.com/watch?v=z5RtZe9AW2E|12W Unregulated Panel vs. 220Ah AGM Bank]]
 ===== specs ===== ===== specs =====
  
 Regardless of type, controllers will have several specifications in common.  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))+  * **rating (or "size")** - this is usually the maximum output in A (amps) 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.    * **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.   * **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.
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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 expensivebut 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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 [[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. [[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.
 +
 +=== panel selection for PWM ===
 +
 +PWM makes the most power when coupled with panels whose operating [[electrical:solar:panels#specifications|Vmp]] is very close to the controller's Absorption ("boost") voltage [[electrical:solar:charge_controller_setpoints|setpoint]].  Since [[electrical:solar:output#panel_temperature|ambient temperatures affect operating Vmp]] the panel's Vmp spec on the label should be about 10% higher than Absorption voltage.  
 +
 +Examples:
 +
 +  * 16.28v Vmp panel spec would be optimal for 14.8v Absorption, as we might use for flooded lead acid.  14.8v x 1.1 = 16.28v.
 +  * 15.62v Vmp panel spec would be optimal for 14.2v Absorption, as we might use for Gel or LiFePO4.  
 +
 +
 +Some [[electrical:solar:panels#thin_film|thin-film]] panels have Vmp in that range but most panels are much higher.  So we find the lowest Vmp practical.  17Vmp panels would perform better on PWM than 18v or 19v.
 ==== 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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 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://web.archive.org/web/20221012213623/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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 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]].
 +
 +== panel selection for MPPT ==
 +
 +MPPT thrives on voltage.  In general, we should select panels that have the highest-practical Vmp while staying safely under the controller's voltage input limit.   MPPT efficiency tends to be greatest when panel voltage is ~twice the charging voltage. The exact ratio varies by controller so read the docs for specifics.  
 +
 +Note that [[electrical:solar:series_vs_parallel|panels can be run in series]] to increase their voltage. 
 +
 +
 +== when PWM beats MPPT ==
 +
 +There are edge cases where an optimal PWM setup can make //more// power than MPPT for a time.  This can happen because MPPT has DC-DC losses that PWM does not, typically ~5%.  Since MPPT harvest from the panel is typically 10-30% greater than PWM the DC-DC losses are hidden.  
 +
 +But when PWM controllers and panels are optimally matched (difference between panel Vmp((actual, not spec)) and Absorption(("boost")) voltage is <5%) then PWM will make a bit more power during Absorption.  
 +
 +
 +
 +
 +
 +
 ==== shunt  ==== ==== shunt  ====
  
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 > ....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. > ....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.
 +
 +=== with Bnn settings ===
 +
 +Units with Bnn settings purport to have Absorption((which they often call Equalization)) profiles for various batteries and configurable Float setpoints. 
 +
 +  * B01 - Sealed lead acid (AGM), typically 14.4v
 +  * B02 - Gel, typically 14.2v
 +  * B03 - flooded lead acid, typically 14.6v
 +  * B04 - 4S LiFePO4 <-- like [[electrical:12v:drop-in_lifepo4|drop-in LFP]]
 +  * B05 - 5S LiFePO4 (uncommon)
 +  * B06 - 3S Li-NMC
 +  * B07 - 4S Li-NMC
 +
 +Absorption duration is unknown.
 +
 +Example manual for controller with [[https://www.botnroll.com/img/cms/FAL09014-Solar-PWM-10A-USB-Manual.pdf|B01-B03]] and [[https://www.solorder.se/image/data/uploads/KLD1210.pdf|B01-B07]].
 +
 +
 +Further viewing:
 +
 +
 +  * [[https://www.youtube.com/watch?v=Fmfnxkh1IFo|basic setup]] by Scott
 +  * [[https://www.youtube.com/watch?v=v-iLu9DS558|setting up the LOAD functions]] by Scott
  
 ==== USB converters ==== ==== USB converters ====
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 [note:  this is a placeholder for a possible new entry.] [note:  this is a placeholder for a possible new entry.]
 There are //DC-DC converting charge controllers// (DDCCC) appearing on the market that claim to be MPPT but do not actually track power points (maximum or otherwise).  They do downconvert some excess voltage into amperage.  See [[https://boondockplan.wordpress.com/2017/12/15/backchannel-dc-dc-converting-charge-controllers/|this blog post]]. There are //DC-DC converting charge controllers// (DDCCC) appearing on the market that claim to be MPPT but do not actually track power points (maximum or otherwise).  They do downconvert some excess voltage into amperage.  See [[https://boondockplan.wordpress.com/2017/12/15/backchannel-dc-dc-converting-charge-controllers/|this blog post]].
 +
 +
 +==== boosting ====
 +
 +Most charge controllers that convert voltage do it by //bucking// (reducing) panel voltage down to the appropriate charging voltages.((normal PWM don't reduce/convert voltage in the normal sense;  they run the panels ~at bank voltage))
 +
 +//Boosting// (voltage-increasing) controllers do exist ([[https://amzn.to/3Rh6QSu|example]]) but they are niche products.  In most cases it makes more sense to increase panel voltage with serial wiring. 
 ==== how to choose ==== ==== how to choose ====
 **PWM is a reasonable default choice** in typical scenarios((12v house power, 12v panels)); they work well enough and are inexpensive. PWM controllers can cost half or a third of their MPPT workmates for any given rated output.((10A, 20A, 40A, etc)) **PWM is a reasonable default choice** in typical scenarios((12v house power, 12v panels)); they work well enough and are inexpensive. PWM controllers can cost half or a third of their MPPT workmates for any given rated output.((10A, 20A, 40A, etc))
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 **MPPT is effectively required** when: **MPPT is effectively required** when:
-  * 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.    +  * 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.  [[https://www.youtube.com/watch?v=V2b7z2eTb5o|Demonstration video from AltE]].
   * 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]]
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 **MPPT may be a better fit** when: **MPPT may be a better fit** when:
  
-  * the existing PWM system is not providing enough output+  * the existing PWM system is not providing enough output but is close (like 10%-20% shortfall)
   * 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]].   * 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.
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 See also [[electrical:solar:shunt_tweaking|shunt tweaking]]. See also [[electrical:solar:shunt_tweaking|shunt tweaking]].
 +
 +==== should I upgrade my PWM to MPPT? ====
 +
 +If the system has changed and now MPPT is required for one of the reason above, then yes.
 +
 +But most people consider this switch to make "more power", forgetting that **solar only makes power when it is demanded**.((for loads or charging))  //If you are presently consuming every watt the system can make// then, yes, replacing PWM with MPPT will likely increase your harvest by ~15%. If you aren't hammering the system then +15% is immaterial; there is no difference in the performance of a 150mph car and a 165mph car in a school zone.
 +
 +So the questions are:
 +
 +  -  do you need more power than you are getting now?
 +  -  would +15% be enough to meet your needs
 +  -  if so, would you pay [whatever the MPPT costs] to get that +15%?
 +
 +There is a saying in solar circles that "adding another panel is a better deal than upgrading from PWM to MPPT."  This may or may not be true in your particular use case.   
  
 ===== multiple charge controllers  ===== ===== multiple charge controllers  =====
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 ==== present use ==== ==== 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).   +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 disconnect]] power relays.  You can define Low Voltage Disconnect (LVD) and Low Voltage Reconnect (LVR) [[electrical:solar:charge_controller_setpoints|setpoints]]  to protect the battery from excessive discharge.
- +
-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 ==== ==== why loads aren't powered from LOAD terminals ====
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 +For an overview of official procedures by manufacturer, see [[https://www.reddit.com/r/vandwellers/comments/12fmyrl/solar_system_is_not_functioning/jfm66y0/|this post]]. 
  
  
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 ===== further reading ===== ===== further reading =====
  
-* [[https://www.solar4rvs.com.au/buying/buyer-guides/choosing-the-right-solar-charge-controller-regulat/|exceptional article on charge controllers]] by Solar4RVs+  * [[https://www.solar4rvs.com.au/buying/buyer-guides/choosing-the-right-solar-charge-controller-regulat/|exceptional article on charge controllers]] by Solar4RVs
electrical/solar/charge_controller.1660068339.txt.gz · Last modified: 2022/08/09 14:05 by frater_secessus