Differences

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

--- electrical:12v:alt_and_solar [2022/12/07 12:15]
frater_secessus [putting it all together]
+++ electrical:12v:alt_and_solar [2024/03/31 17:05] (current)
frater_secessus [how alternator charging helps]
@@ Line 1: / Line 1: @@
-Note:  although this page was written with alternator-augmented solar charging in mind, the general principles also apply to solar+[[electrical:shore_power|shore power charging]] and solar+[[electrical:generator|generator]] charging.
+Note:  although this page was written with alternator-augmented solar charging in mind, the general principles also apply to solar+[[electrical:shore_power|shore power charging]] and solar+[[electrical:generator|generator]] charging. Also see [[electrical:12v:power_mix|Deciding on a Power Mix]].
+> Solar and DC-DC alternator charging are going to be the best practices for maintaining charge in one's battery bank. It only requires a little math, a little discipline to stick with the math, and the right expectations about solar intake.  -- CMDR_Schrodinger((https://www.reddit.com/r/vandwellers/comments/15z8eh6/energy_management_during_trips/jxfv03f/))
-[[lifestyle:words_of_wisdom|Words of wisdom]]: "Bulk charging requires //current//. Absorption requires //relatively high voltage// and //time at that voltage//." - secessus
 ====== Augmented solar charging ======
@@ Line 15: / Line 17: @@
 Solar works anytime there is available sunlight, not just when the vehicle is running.
-Alt charging alone is unlikely to get lead-acid chemistries fully charged since Absorption can take hours and alternators often cannot hold [[electrical:solar:charge_controller_setpoints|the required voltage]]. Incomplete charge ([[electrical:12v:psoc|Partial State of Charge]], or PSOC) over time will result in [[electrical:batterycide|battery murder]].
+Solar can meet both the **voltage** and **time** requirements necessary for [[electrical:12v:charging|complete charging]];  this is critical with lead-acid chemistries which will otherwise suffer damage from [[electrical:12v:psoc|partial states of charge]].
 How to avoid (or attenuate) battery murder with this scenario:
   * get access to shore power every couple of days to get the bank fully charged.  This will retard the murderification process; or
   * use a different (and $$$) battery alternative like LiFePO4 (no problems with PSOC) or carbon foam (needs full charge every couple of weeks?); or
-  * add in a small amount of solar.
+  * add in a small amount of solar <-- what this article is about
@@ Line 27: / Line 29: @@
 From ~80% to 100% (Absorption stage) charging requires little current but a long time holding at a relatively high voltage.  So in our alt+solar scenario the alternator does the heavy lifting in the beginning then a small solar install does the light (but lengthy) work at the end.((The solar will also contribute during Bulk when the sun is shining.))
-Having a bit of solar may mean you can us a simpler/cheaper isolator rather than a more $$ [[electrical:12v:b2b|DC-DC charger]].
+Having a bit of solar may mean you can use a simpler/cheaper combiner rather than a more $$ [[electrical:12v:b2b|DC-DC charger]].
 ===== how alternator charging helps =====
+Alternator charging is extremely powerful and cheap compared to typical solar installs.  It works best when solar works worst:  when the batteries are deeply discharged in the morning.  The sun is weak then but the bank needs a large supply of current (early [[electrical:12v:charging#bulk_stage|Bulk charging]]).
-Solar power is relatively weak and expensive((for the amount of power produced)) compared to alternator charging.  Solar is most challenged in the morning when the bank is deeply discharged.  The sun is weak then but the bank needs a large supply of current (early [[electrical:12v:charging#bulk_stage|Bulk charging]]).
+[[electrical:solar:charge_controller#pwm|PWM]] controllers are especially hamstrung in this scenario;  since they run the panels at battery voltage (Vbatt) they produce the least power exactly when the most power is required.  By the time alternator voltage (Valt) is reached PWM controllers are able to produce meaningful power.
-[[electrical:solar:charge_controller#pwm|PWM]] controllers are especially hamstrung in this scenario;  since they run the panels at battery voltage (Vbatt) they produce the least power exactly when the most power is required.  By the time Valt is reached PWM controllers are able to produce meaningful power.
+Alt charging shovels current into the bank until Valt is reached, at which point it begins to taper off.  Solar can take it from there.  A good metaphor might be a two-stage rocket:  the alternator does the heavy lift getting the rocket off the ground then the solar charging takes care of the high altitude, high speed duties.
-Alt charging shovels current into the bank up to the point that alternator voltage (Valt) is reached.  Solar can take it from there.  A good metaphor might be a two-stage rocket:  the alternator does the heavy lift getting the rocket off the ground then the solar charging takes care of the high altitude, high speed duties.
 > Use a generator or alternator to get to 85% SOC or so early in the AM, then let Solar spend all day polishing off the last 15% because that takes time more than amps. - a64pilot((https://www.cruisersforum.com/forums/f14/time-it-takes-to-fully-charge-batteries-238875-9.html#post3223983))
+The alternator can help meet [[electrical:12v:charging#charging_current|lead bank minimum charging current requirements]].
 ===== optimal alternator contribution =====
-Broadly speaking, alternator/generator charging is most effective **in the morning**.  There are several factors in play here.
+Broadly speaking, //alternator charging is most effective in the morning// and //solar charging is most effective at local solar noon//.  This pattern is most evident when using isolators/relays and/or lead chemistry batteries, and less evident when using [[electrical:12v:b2b|DC-DC chargers]] and/or lithium chemistries.
+There are several factors in play here.
 ==== charging stage ====
-During [[electrical:12v:charging#bulk_stage|Bulk charging stage]] the bank will accept maximum current.((by definition))  **Bulk typically coincides with early morning**.
+During [[electrical:12v:charging#bulk_stage|Bulk charging stage]] the bank will accept maximum current.((by definition))  For most 'dwellers alternator charging current will outstrip solar charging current, making alternator charging most helpful during bulk.  //Bulk typically coincides with early morning.//
 ==== voltage delta ====
@@ Line 71: / Line 76: @@
 Since the output of solar charge controllers is relatively high (typically the same setpoints as the DC-DC charger), **the ability of an isolator to contribute current is reduced as solar harvest comes into play**.
+==== PWM solar charge controllers ====
+Getting bank voltage up earlier will also keep PWM solar charge controllers from getting [[electrical:solar:pwm_tweaking#pwm_s_achilles_heel|hamstrung due to low Vbatt]].  MPPT controllers are not affected by Vbatt.
 ==== putting it all together ====
@@ Line 84: / Line 93: @@
   - the Li voltage curve is very flat in the middle, so the voltage delta will be stable through the "middle 80%"
-  - for average users, Li will not have an Absorption stage in the lead-chemistry sense.((advanced users may find [[electrical:12v:electrical:12v:drop-in_lifepo4#mythlithium_doesn_t_need_absorption|exceptions]] to this general statement))
+  - for average users, Li will not have an Absorption stage in the lead-chemistry sense.((advanced users may find [[electrical:12v:drop-in_lifepo4#mythlithium_doesn_t_need_absorption|exceptions]] to this general statement))
   - Lithium is often charged with DC-DC, which charges at the ~same voltage as solar

RV and vandwellers wiki

User Tools

Site Tools

Differences

Page Tools