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--- lifestyle:faq_solar_generator [2023/05/17 09:38]
frater_secessus [pass-through charging]
+++ lifestyle:faq_solar_generator [2024/02/05 18:50] (current)
princess_fluffypants
@@ Line 1: / Line 1: @@
+====== Solar generators ======
 Words of wisdom:  "These aren't aimed at people that know what they are doing." -- [[https://www.reddit.com/r/vandwellers/comments/dr387z/500w_aimtom_rockpals_500_solar_generator_review/f6jc7lz/|LastTreeStar]]
+===== TL;DR =====
+**These things are //EXTREMELY// expensive for the capacity, however they do offer a lot of convenience.** For those with plenty of money who value ease and speed over capacity and run-time, an argument can be made for these if your power needs are small-to-medium and you are only taking short trips in your vehicle.
-====== Solar generators ======
 [[https://amzn.to/2MZhjzi|{{ https://images-na.ssl-images-amazon.com/images/I/51ug3IIF-zL._AC_US218_.jpg}}]]
-"Solar Generators" ([[https://amzn.to/2E7EG71|power stations]], power packs) are self-contained devices that contain:
+"Solar Generators" ([[https://amzn.to/2E7EG71|power stations]], power packs) are not actually generators. They are basically just a self-contained electrical system in a box, containing:
-  * A battery pack, often lithium or AGM
+  * A [[electrical:12v:batteries|battery]], usually lithium
   * USB outlet[s] and 12v outlet[s]
   * An [[electrical:inverter|inverter]]
@@ Line 14: / Line 18: @@
 These devices are packaged for convenience and are usually much more expensive than the components bought separately.  Sometimes manufacturers use non-standard panel connectors to keep customers in an expensive "walled garden", referring to normal, non-proprietary panels as [[https://inergytek.com/pages/support|"off_brand"]].((COUGH [[https://amzn.to/2SpgjbR|inergy]] COUGH))
-Less expensive "solar generators" may cut corners by using more basic batteries (AGM vs Lithium), cheaper inverters (Modified sine wave instead of pure sine wave), or less efficient solar charge controllers (PWM instead of MPPT).
+Less expensive "solar generators" may cut corners by using more basic batteries (AGM vs Lithium), cheaper inverters (Modified sine wave instead of pure sine wave), or less efficient solar charge controllers (PWM instead of MPPT).  These lower-end models tend to have very restricting charging limits not found on DIY systems.
 The overall proposition can be summed up by the title of a Bob Wells video, [[https://www.youtube.com/watch?v=gFOZ6aetIPc|Should you Buy a Jackery Power Station? Super Easy but Super Expensive]].
@@ Line 42: / Line 46: @@
 Specs for these devices are often given in nonstandard or even misleading ways.  The following discussion will use the Yeti shown above, although their product description is better than most.
+==== TLDR ====
+We are most interested in
+  * how much capacity the bank has (typically in Watt-hours, Wh)
+  * charging limits
+    * by car adapter (typically ≤120w because of limitations of the ciggy port)
+    * by wall adapter (volts and amps, sometimes the stock wall charger makes lower power than is otherwise possible)
+    * by solar ([[electrical:solar:panels#specifications|Voc]] and input current, which will dictate which panels and how many are suitable)
+  * DC output (typically 10A at 12v)
+  * AC output (given as Watts, the biggest AC loads you can run)
 ==== capacity ====
-Ah are often expressed as mAh.  Which is more impressive, 33Ah or 33,000mAh?  They are the same capacity expressed in different ways.
+Capacity is most often listed in Wh (watt-hours), which makes comparison quite easy.  Some (especially lead cells) retain Ah ratings.  For lead batts, 12v x the Ah rating = Wh.  Sometimes Ah are expressed as mAh, or 1/000th of an Amp.  Which is more impressive, 33Ah or 33,000mAh?  They are the same capacity expressed in different ways.
+Nefarious marketers sometimes multiply each cell's Ah rating times the number of cells, resulting in a 3x inflation of Ah rating.
-The 33Ah **capacity** lead-acid battery in the example above is stated as 400Wh.  This is technically correct but mixes units in a way that consumers may not understand.  Consumers may also not realize that lead-acid chemistries are usually only drawn down to 50% [[electrical:depth_of_discharge|depth of discharge]], giving an actual usable capacity of 16.5Ah.  In addition, lead-acid battery [[electrical:12v:battery_capacity|capacities]] are measured over 20hrs.  With our example this means a **10w** continuous DC load in this case, or 9w from the built-in inverter.  Loads greater than those will decrease usable capacity due to the [[https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&uact=8&ved=2ahUKEwjNo6ayjbXgAhXJwVQKHZ7xAmAQFjAAegQIChAB&url=https%3A%2F%2Fen.wikipedia.org%2Fwiki%2FPeukert%2527s_law&usg=AOvVaw0guPoMgsy0smO6ISiV1t32|peukert effect]].
-Nefarious marketers sometimes multiply each cell's Ah rating times the number of cells, resulting in a 3x inflation of Ah rating.  \\
+=== usable capacity ===
-On the upside, they have almost no peukert effect and therefore can support heavier loads (at the expense of running time).  Also, higher end units run 4S or higher voltages then downconvert them for a ~13v output much closer to what nominal 12v devices expect.
+Most people know that only about 50% of lead batt capacity should be used in order to ensure a long life.  Lithium also has a recommended safety margin, 20%.  This means 80% of the rated capacity can be used and still hit the manufacturer's cycle life claims.  400Wh x 0.8 = 320Wh usable.
+With 320Wh usable we could run the a theoretical 400w inverter at max load for 48minutes.  (320Wh / 400W x 60 minutes)
-You could run run [[electrical:12v:loads|a load]] at the **inverter's 300W normal rating** for ~36 minutes.((including 10% efficiency loss on inversion, but not including peukert effect))  Some manufacturers will list the inverter's peak output (600w in this case) in the title as if it were the amount of power the unit could deliver over time.  New folk sometimes read this as "I can run 600w of appliances off the unit forever!", forgetting this is a //peak// load and that the unit has a finite capacity.
 ==== cell chemistry ====
@@ Line 79: / Line 95: @@
 Inverters are typically rated on their //continuous// output but unscrupulous marketers may list the //peak// load, which is a temporary overload.
-==== solar charging limits ====
+==== solar input ====
+If the [[electrical:solar:charge_controller|controller type]] isn't claimed to be MPPT it is likely PWM.
+=== solar charging limits ===
 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.
-  * **current** limit - 3A is a common input current limit on smaller, less-expensive 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.  MPPT controllers with the same limit might run the panels at 18v:  18v x 3A = 54w.((minus DC-DC conversion losses of ~5%))
+  * **current** limit - 3A is a common input current limit on smaller, less-expensive 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.
+    * 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%))

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