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electrical:solar:charge_controller [2024/04/16 20:28]
frater_secessus [specs] 		electrical:solar:charge_controller [2025/02/28 14:09] (current)
frater_secessus [specs]
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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 =====
  
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   * **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))   * **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))
 +  * **Maximum input current** is uncommon in standalone MPPT controllers but common in [[12v:sg_troubleshooting#must_i_use_the_ps_brand_s_proprietary_solar_panels|the controllers built into "power stations"]].  It is also a factor with PWM controllers. 
  
 ===== Types of charge controllers ===== ===== Types of charge controllers =====
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 [[electrical:12v:multipoint_charging|Multiple controllers (with separate arrays) can be used to charge a common bank]].  The controllers should be configured with similar charging setpoints for the greatest efficiency.((http://www.morningstarcorp.com/parallel-charging-using-multiple-controllers-separate-pv-arrays/)) [[electrical:12v:multipoint_charging|Multiple controllers (with separate arrays) can be used to charge a common bank]].  The controllers should be configured with similar charging setpoints for the greatest efficiency.((http://www.morningstarcorp.com/parallel-charging-using-multiple-controllers-separate-pv-arrays/))
 ===== sizing your charge controller ===== ===== sizing your charge controller =====
-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/))  +NOTE:  in no case can the panel voltage limit be exceeded.  
-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]]+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, weigh more, and take up more space.  An undersized CC will either not perform well (MPPT) or be damaged (PWM).   
 + 
 +==== PWM ==== 
 + 
 +PWM controllers are sized based on the **maximum input power** they will ever see.   
 + 
 +One 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/)) A faster, cruder method is (panel wattage / 10) = charge controller amps.  
 + 
 + 
 +==== MPPT ==== 
 + 
 +MPPT controllers are sized based on the **average power** they will see.   
 + 
 + 
 +The approach is different because  
 + 
 +  * MPPT are expensive 
 +  * MPPT can trim incoming power to avoid exceeding their output rating 
 + 
 +So MPPT controllers generally have [[electrical:solar:overpaneling|more panel put on them than their rating would suggest]] ("overpaneling"). 
 + 
 + 
 +There are a few ways of calculating this.  The Victron MPPT calculator is quite good.  It will generally suggest 10-30% overpaneling. 
 + 
 +You can ballpark it manually by dividing *panel wattage / 14.25v((this appears to be the constant used in the Victron calculator))).  Example: 
 + 
 +''400w / 14.25v = 28.0702A'' 
 + 
 +  * 28.0702 / 25A candidate = 3.0702A.  (3.0702A / 25A) = **12.28% overpaneled**.  On the lower end of Victron's overpaneling recommendation. 
 +  * 28.0702 / 20A candidate = 8.0702A.  (8.0702A / 20A) = **40.35% overpaneled**.  This exceeds Victron's overpaneling recommendation. 40% overpaneling might be fine at higher latitudes like Canada or Alaska, but the controller would be maxxed out quite often elsewhere.   
 + 
 +**Conclusion**:  25A is appropriate for  400w of panel.  
 + 
 + 
 +25A? 20A? 
 + 
 + 
 + 
 +  - (28.0702A - 25A) =  
 ===== overpaneling ===== ===== overpaneling =====
 this section [[electrical:solar:overpaneling|has been moved]]. this section [[electrical:solar:overpaneling|has been moved]].
electrical/solar/charge_controller.1713313697.txt.gz · Last modified: 2024/04/16 20:28 by frater_secessus

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