Differences

This shows you the differences between two versions of the page.

--- electrical:solar:charge_controller [2023/09/06 12:05]
frater_secessus [MPPT]
+++ electrical:solar:charge_controller [2023/09/10 13:51]
frater_secessus [present use]
@@ Line 56: / Line 56: @@
 [[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 ====
 [[http://amzn.to/2iD3WKf|{{ https://images-na.ssl-images-amazon.com/images/I/51bi9IjcsRL._AC_US160_.jpg}}]]
@@ Line 86: / 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 225: / Line 244: @@
 ==== 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 ====

RV and vandwellers wiki

User Tools

Site Tools

Differences

Page Tools