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--- lifestyle:faq_solar_generator [2024/05/09 17:49]
frater_secessus [Best case scenario] added troubleshooting
+++ lifestyle:faq_solar_generator [2024/08/05 02:08] (current)
frater_secessus [solar input]
@@ Line 103: / Line 103: @@
 === solar charging limits ===
+also see [[12v:sg_troubleshooting#must_i_use_the_ps_brand_s_proprietary_solar_panels|this article]] on choosing panels for a SG
 Many smaller units have quite restrictive solar input limits.
-  * **voltage** - 22Voc is a common voltage limit, effectively limiting one to [[electrical:solar:panels#panel_voltage|12v nominal]] panels.
+  * **voltage** - 24Voc is a common voltage limit, effectively limiting one to [[electrical:solar:panels#panel_voltage|12v nominal]] panels. **Input voltage limits must not be exceeded**.  Note:  some very large units have high input //minimums//, like 50v.
-  * **current** limit - 3A is a common input current limit on smaller, less-expensive units.
+  * **current** limit - 3A is a common input current limit on smaller, less-expensive units.  8A is a common limit on larger units.
-    * With PWM controllers the max power harvestable will be 3A x [internal battery voltage], which can be as low as 9v.  9v x 3A 27w.
+    * With PWM controllers the max power harvestable will be 3A x [internal battery voltage], which can be as low as 9v.  9v x 3A 27w.  **PWM input current limits must not be exceeded**
-    * MPPT controllers with the same limit might run the panels at 18v, the Vmp:  18v x 3A = 54w((minus DC-DC conversion losses of ~5%))
+    * MPPT controllers with the same limit might run the panels at 18v, the Vmp:  18v x 3A = 54w((minus DC-DC conversion losses of ~5%))  MPPT  incoming current limits can usually be exceeded; the controller will throttle back incoming current to hold the limit. The allowable amount of overpanel is [[electrical:solar:overpaneling#vs_charge_controller|well-documented with most standalone MPPT controllers]] but "power stations" are usually black boxes with no published overpanel spec.  Proceed at your own peril.
+== the Amp bottleneck ==
+Because the Amp limit is usually the limiting factor for MPPT power production.  Selecting a panel with a Voc((//not// Vmp)) closer to the unit's input limit((with some headroom)) can make maximal power given the limitations.  This is because for a given rated output like 100w a higher Vmp (volts) means a lower Imp (amps).
+  * 22.5Voc panel - Vmp ~18v.((Vmp is typically 0.8 of Voc)) 18v x 8A limit = **144w**.
+  * 21Voc panel - Vmp ~16.8v.  16.8v x 8A limit = **134w**.

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