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--- electrical:solar:charge_controller [2023/09/06 12:18]
frater_secessus [PWM]
+++ electrical:solar:charge_controller [2023/09/26 11:25]
frater_secessus [how to choose]
@@ Line 98: / Line 98: @@
 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 ==
@@ Line 216: / Line 223: @@
 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 237: / Line 258: @@
 ==== 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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