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--- opinion:frater_secessus:run_this_load [2024/04/20 22:30]
frater_secessus created
+++ opinion:frater_secessus:run_this_load [2025/02/10 13:15] (current)
frater_secessus [recharging afterward]
@@ Line 1: / Line 1: @@
+[also see [[food:refrigeration:power|How do I run a 12v compressor refrigerator?]]]
 ====== What will it take to run this load? ======
@@ Line 6: / Line 8: @@
 There are several factors:
+  - AC vs DC, voltage.   typically 12v**dc** or 120v**ac**
   - current (power), in Amps (A)
   - Watt-hours (Wh) ((or Amp-Hours)) (energy)
-  - recharging afterward
+  - any [[electrical:12v:power_mix|charging sources]] that are active at the time
+  - **recharging afterward**
+And a couple formulas we will use to convert units back and forth:
   - Watts = Volts x Amps.
   - Amps = Watts / Volts.
@@ Line 14: / Line 21: @@
 [[opinion:frater_secessus:pareto|about these summaries]]
+===== AC/DC =====
+Using the US as an example:
+  * wall outlets are 120v AC (alternating current).  In a van this kind of load will have to be run off [[electrical:shore_power|shore power]] or [[electrical:inverter|an inverter]].
+  * most vehicles run on 12v DC (direct current).  Very small 12vdc loads (≤120w or 10A) can be run off the 12v outlet.  Larger loads will be run off [[electrical:12v:intro|an aux power setup]].
@@ Line 43: / Line 59: @@
-==== watt-hours ====
+===== watt-hours =====
+Energy use ([[electrical:12v:dailypowerrequirements|daily power requirement]]) is often represented in Watt-hours, although Amp-hours will also work.
 This is time (hours) x watts.  Our 518W (39.3A at 12v) load run for 20 minutes would be ~173Wh (518 x 20 minutes / 60 minutes in an hour) or 13.1Ah.
+Battery chemistries have recommended depths of discharge.
+  * Lead batts are usually run down to 50%, so we would need at least 28.8Ah of lead to run our 173Wh load for one day (173Wh / 0.5 / 12.0v nominal).
+  * LiFePO4 batts are usually run down to 20%, so we would need at least 16.9Ah of LFP to run our 173Wh load for one day (173Wh / 0.8 / 12.8v nominal).
+Then multiply by the "days of autonomy" (ie, without recharging).  If you want two days then multiply the above by 2, for example. If you know you will be able to recharge fully each day then days of autonomy is 1.
+Note that running loads while sufficient charging is active is basically a freebie and does not count against the battery capacity.((it //will// slow down recharging if done during Bulk or and //may// slow down recharging in Absorption stages))
 ===== recharging afterward =====
+This is the part that people often forget (or prefer not to think about) in the planning stage.  Yes, your power station with a 1500w inverter can run that 1500w load for an hour, but **if you can't recharge it then it can do this trick only once**.   It's like paying rent:  being able to afford the first month's rent out of savings is one thing, but one needs income to keep paying the monthly rent to keep living there.
 If you are recharging LiFePO4 the 173Wh used is basically what you'd need to recharge that battery to its former state of charge.

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