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--- electrical:solar:charge_controller [2023/09/06 12:23]
frater_secessus [MPPT]
+++ electrical:solar:charge_controller [2024/04/16 20:28] (current)
frater_secessus [specs]
@@ Line 29: / Line 29: @@
 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.
   * **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))
@@ Line 182: / Line 182: @@
 [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]].
+==== 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 ====
 **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))
@@ Line 190: / Line 197: @@
 **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.  [[https://www.youtube.com/watch?v=V2b7z2eTb5o|Demonstration video from AltE]].
   * 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]]
@@ Line 223: / Line 230: @@
 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  =====
@@ Line 244: / Line 265: @@
 ==== 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 ====

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