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--- electrical:autonomy [2024/07/16 12:43]
frater_secessus [economic factors]
+++ electrical:autonomy [2025/06/16 13:28] (current)
frater_secessus [thinking in whole days]
@@ Line 6: / Line 6: @@
 ===== TL;DR =====
-  * Days of autonomy (or reserve) is the number of days of power one stores for periods of reduced or non-existent charging.
+  * Days of autonomy (or reserve) is the number of days of power one stores for days when charging is unavailable.  It is planning for the Worst Case Scenario.
   * A system whose [[electrical:12v:battery_capacity|capacity]] == [[electrical:12v:dailypowerrequirements|daily power requirements]] has one day of autonomy;  24 hours after a full charge there will be no usable capacity left.
-  * Depending on [[electrical:12v:power_mix|charging sources]] we might think in whole or fractional days
+  * Depending on [[electrical:12v:power_mix|charging sources]] it might be more useful to think fractional days rather than whole ones
 [[opinion:frater_secessus:pareto|about these summaries]]
-  * the decision on how much capacity to purchase is economic as well as technical
+  * the decision on how much capacity to purchase is economic as well as technical.
+  * it is possible to reduce the days of autonomy required by reducing consumption on days with less or no charging
@@ Line 20: / Line 21: @@
   * [[electrical:shore_power|shore power]] charging with [[electrical:converter|a converter]] or other charger
+  * charging  by [[electrical:12v:mandatory_solar|alternator alone]] but not driving some days
   * no field charging at all (charging at home only, no charging over weekend outings)
@@ Line 110: / Line 112: @@
 If your LFP has a 0.5C constant discharge rating then doubling the Ah capacity doubles the load current you can apply to the bank.
+===== minimizing the required days of autonomy =====
+  * reduce optional power consumption during periods of low solar harvest.  For example, one's //average// consumption might be >2kWh/day but one might only //need// 1kWh/day when power is tight.
+  * think in fractional days of autonomy (see above)
+  * If your schedule is flexible you might adjust your plans for days where it is forecast to be rainy/overcast/whatever:
+    * plan your relocation drives for those days so you can take advantage of [[electrical:12v:alternator|charging by alternator]]
+    * if you schedule a day in a paid campsite from time to time to dump tanks and take on water, do so on projected days of poor solar harvest.  This way you can also [[electrical:converter|charge from the power pedestal]].
+  * assuming you have space, max out the roof with as much used [[electrical:solar:panels#panel_voltage|higher-voltage panel]] as will fit.  600w of used can cost the same as 200w of new, and power harvest would be tripled in poor conditions.
+  * a small portable array on its own controller can punch far above its weight:  sit it out in the sun angled correctly when you are hiding in shade or in winter when sun is low in the sky
+  * it's a bit extreme, but a [[electrical:12v:alternator_details#external_regulation|second alternator setup with external regulation]] might be cheaper than a a huge bank of premium LiFePO4.  Setups like this can yield maximal alternator charging without risking overheating.

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