Differences

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

--- electrical:solar:charge_controller [2023/04/11 15:57]
frater_secessus [Solar charge controllers] pareto
+++ electrical:solar:charge_controller [2024/04/16 20:28] (current)
frater_secessus [specs]
@@ Line 2: / Line 2: @@
 ====== Solar charge controllers ======
-===== Pareto summary =====
+===== TLDR =====
   * solar panels -> solar charge controller (SCC) -> battery bank
   * the SCC's main job is preventing //battery overcharge//
-  * the two main types of SCC are PWM and MPPT
+  * The two main types of SCC are PWM and MPPT
-  * SCC LOAD outputs are vestigal features but may be useful for triggering certain loads
+    * PWM - Cheaper, less efficient
+    * MPPT - More expensive, but more efficient
+  * SCC LOAD outputs are vestigial features but may be useful for triggering certain loads
@@ Line 27: / 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 54: / 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 68: / Line 82: @@
 This ability to decouple panel and bank voltage can result in 10%-30% more power harvested from 12v nominal panels than with a PWM controller, depending on conditions.  //Average// daily production with MPPT is typically ~+15%((https://web.archive.org/web/20221012213623/https://www.redalyc.org/journal/849/84959429001/html/)), which may or may not justify the added cost on its own.
@@ Line 83: / 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 ==
+There are edge cases where an optimal PWM setup can make //more// power than MPPT for a time.  This can happen because MPPT has DC-DC losses that PWM does not, typically ~5%.  Since MPPT harvest from the panel is typically 10-30% greater than PWM the DC-DC losses are hidden.
+But when PWM controllers and panels are optimally matched (difference between panel Vmp((actual, not spec)) and Absorption(("boost")) voltage is <5%) then PWM will make a bit more power during Absorption.
 ==== shunt  ====
@@ Line 115: / Line 149: @@
 > ....a rather inexpensive piece of equipment but it doesn’t do a terrible job of being a basic solar charge controller. On the whole, it behaves as one may expect – protecting the battery from excessive voltage and overdischarge, with an integrated dusk timer function and USB outputs...what do you expect for $10-20? Something that works is already a big surprise to me.
+=== with Bnn settings ===
+Units with Bnn settings purport to have Absorption((which they often call Equalization)) profiles for various batteries and configurable Float setpoints.
+  * B01 - Sealed lead acid (AGM), typically 14.4v
+  * B02 - Gel, typically 14.2v
+  * B03 - flooded lead acid, typically 14.6v
+  * B04 - 4S LiFePO4 <-- like [[electrical:12v:drop-in_lifepo4|drop-in LFP]]
+  * B05 - 5S LiFePO4 (uncommon)
+  * B06 - 3S Li-NMC
+  * B07 - 4S Li-NMC
+Absorption duration is unknown.
+Example manual for controller with [[https://www.botnroll.com/img/cms/FAL09014-Solar-PWM-10A-USB-Manual.pdf|B01-B03]] and [[https://www.solorder.se/image/data/uploads/KLD1210.pdf|B01-B07]].
 Further viewing:
@@ Line 131: / 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 139: / 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 152: / Line 210: @@
 **MPPT may be a better fit** when:
-  * the existing PWM system is not providing enough output
+  * the existing PWM system is not providing enough output but is close (like 10%-20% shortfall)
   * nominal 12v panels have a relatively high Vmp (>=18v) for [[https://www.reddit.com/r/vandwellers/comments/bmlosu/is_vandwelling_a_frugal_lifestyle/emz5lsf/?context=1|reasons discussed here]].
   * battery banks are cycled deeply on a regular basis so more time is spent at low Vbatt where PWM struggles.
@@ Line 172: / 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 193: / 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 ====
@@ Line 230: / Line 300: @@
+For an overview of official procedures by manufacturer, see [[https://www.reddit.com/r/vandwellers/comments/12fmyrl/solar_system_is_not_functioning/jfm66y0/|this post]].

RV and vandwellers wiki

User Tools

Site Tools

Differences

Page Tools