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--- electrical:solar:charge_controller_setpoints [2019/09/10 10:31]
frater_secessus [Solar charge controller setpoints]
+++ electrical:solar:charge_controller_setpoints [2020/01/07 21:43]
frater_secessus [charging setpoints]
@@ Line 5: / Line 5: @@
 ===== charging setpoints =====
-  * **Float voltage (Vfloat)** - the voltage the battery bank is held at during [[electrical:12v:charging#float_stage|Float]].  Common setpoint in most configurable controllers.
+Charging setpoints are configured in accordance with the battery manufacturer's recommendations.  These are often found in manuals and spec sheets.  For example, [[https://www.trojanbattery.com/pdf/Trojan_QSG_AGM.pdf|Trojan's recommendations for charging their AGM batteries]] looks like this:
-  * **Absorption voltage (Vabs)** - the voltage the battery bank is held at during [[electrical:12v:charging#absorption_stage|Absorption]].  Common.
+{{ :electrical:solar:trojan.png?400 |}}
+Note that simpler charge controllers only have preconfigured presets like "FLOODED" or "AGM" and don't let you set exact setpoints.  If this is the case pick the closest preset to the recommendations and understand you will likely not get full performance or lifetime from the battery bank.
+  * **Absorption voltage (Vabs)** - the voltage the battery bank is held at during [[electrical:12v:charging#absorption_stage|Absorption stage]].  In this case the recommendation is 14.4v.
+  * **Float voltage (Vfloat)** - the voltage the battery bank is held at during [[electrical:12v:charging#float_stage|Float]].  In this case the recommendation is 13.5v.
+  * **Maximum charge rate:**  While maximum charge rates normally are immaterial to solar charging, Trojan specfies a maximum of [[electrical:12v:battery_capacity|C]]/5, or 1/5th of the battery's capacity in Ah.
+  * **Minimum charge rate:**  not stated in our example, but typical minimum charging values are ~C/10 for lead chemistries.
+  * **Temperature compensation** - how the voltage setpoints are adjusted for temperature.  While this is sometimes configurable, generally the compensation factor is close enough between manufacturers that it can be left at the default.
+  * **Absorption termination** - the amount of current (or percentage of capacity) Absorption falls to before completion.  This is used to decide when the controller should go to Float.  It's not given in this chart, but elsewhere
+Less common setpoints:
   * **Absorption duration** - the amount of time Vabs will be held until dropping to Vfloat.  Somewhat common.
-  * **Absorption termination** - the amount of current (or percentage of capacity) Absorption must fall to before dropping to Vfloat.  Not common.
   * **Absorption restart** - voltage (or duration) at which Absorption stage after failing to maintain Vfloat

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