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electrical:solar:charge_controller [2023/09/26 11:25]
frater_secessus [how to choose] 		electrical:solar:charge_controller [2024/06/01 22:01] (current)
frater_secessus [sensors]
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 Cautionary example:  [[https://www.youtube.com/watch?v=z5RtZe9AW2E|12W Unregulated Panel vs. 220Ah AGM Bank]] Cautionary example:  [[https://www.youtube.com/watch?v=z5RtZe9AW2E|12W Unregulated Panel vs. 220Ah AGM Bank]]
 +==== sensors ====
 +
 +To charge correctly the controller needs to know the precise voltage and temperature of the battery bank.  
 +In the best case scenario these measurements are done with an external **temp sensor** and **voltage sense**((not a typo, it's called voltage sense)) that plug into the controller or talk to the controller via bluetooth. 
 +
 +In the absence of external sensors the controller tries to use any internal sensors it might have.  The values will be inaccurate: 
 +
 +  * battery voltage will read [[electrical:12v:voltage_sag|falsely high during charging]], and
 +  * temperature will read falsely high because of the heat the controller generates from its own electronics
 +
 +With **lead-chemistry batteries** both conditions can cause [[electrical:12v:psoc|chronic undercharging]], a key cause of [[electrical:batterycide|premature battery failure]].  Many **LiFePO4 batteries** have their own [[opinion:frater_secessus:agm2lifepo4#wait_lfp_can_be_damaged_by_charging_in_cold_weather|low temperature charging cutoff]] but those that do not must rely on the charger to disconnect when battery temps are ~freezing.
 +
 +
 +
 +
 ===== 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.
 +  * **Minimum input voltage** - a PWM controller will requires panel voltage ≥ battery voltage to charge.  MPPT controllers will usually require a bit more voltage headroom to start/run the MPPT algorithm.((although less common, //boosting// MPPT do exist that can increase incoming voltage in order to charge a higher-voltage battery bank))
  
  
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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:
   * when one needs to squeeze every watt out of the panel   * 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.  [[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]]
electrical/solar/charge_controller.1695741930.txt.gz · Last modified: 2023/09/26 11:25 by frater_secessus

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