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electrical:12v:dailypowerrequirements [2022/10/14 14:15]
frater_secessus [How much power do I need to run stuff?] 		electrical:12v:dailypowerrequirements [2024/02/08 11:22] (current)
frater_secessus [now what?] power mix
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 ====== How much power do I need to run stuff? ====== ====== How much power do I need to run stuff? ======
  
-It may seem from the outside, but all we really need are+It may seem overwhelming at first, but all we really need are
  
   - a list of things you intend to run in the van.  Be //specific// and //thorough//.  <- the hardest part.    - a list of things you intend to run in the van.  Be //specific// and //thorough//.  <- the hardest part. 
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   * Most are in watts, which we will use directly for our math.     * Most are in watts, which we will use directly for our math.  
   * Sometimes they don't show watts but only Amps and Volts (example: **120vac, 2A**).  **Amps x volts = watts**, so our example would consume **240w**.  Easy peasy.   * Sometimes they don't show watts but only Amps and Volts (example: **120vac, 2A**).  **Amps x volts = watts**, so our example would consume **240w**.  Easy peasy.
 +  * the rated power is often the //max// power the device can consume.  They may use less over time (a laptop with a 90w adapter may pull 90w only when running at 100%); to know for sure use [[electrical:inverter#kill-a-watt|a kill-a-watt]] to measure actual energy use over a full day or more. 
  
 ===== how long will you run each load? ===== ===== how long will you run each load? =====
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 Aside:  if you haven't made or used a spreadsheet before, here is [[https://www.youtube.com/watch?v=7Q2C9MB-YH4|a beginner's intro]] on youtube. Many computers come with a spreadsheet program (like Excel) and there are free ones like [[https://www.libreoffice.org/discover/calc/|LibreOffice Calc]] and free online ones like [[https://docs.google.com/spreadsheets/u/0/|Google Sheets]], etc. Google Sheets was used for the screenshots in this article. Aside:  if you haven't made or used a spreadsheet before, here is [[https://www.youtube.com/watch?v=7Q2C9MB-YH4|a beginner's intro]] on youtube. Many computers come with a spreadsheet program (like Excel) and there are free ones like [[https://www.libreoffice.org/discover/calc/|LibreOffice Calc]] and free online ones like [[https://docs.google.com/spreadsheets/u/0/|Google Sheets]], etc. Google Sheets was used for the screenshots in this article.
 +
 +
 ===== building a more accurate estimate ===== ===== building a more accurate estimate =====
  
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   * this is a giant PITA for only two loads.  But when you get to ten or twenty (or more) loads the spreadsheet starts to shine.  It also allows you to easily see the increase/decrease from using, say, a 45w or 90w fridge instead of a 60w one.    * this is a giant PITA for only two loads.  But when you get to ten or twenty (or more) loads the spreadsheet starts to shine.  It also allows you to easily see the increase/decrease from using, say, a 45w or 90w fridge instead of a 60w one. 
  
 +===== also consider your highest-current loads =====
 +
 +Sometimes a load doesn't use much energy (Wh) because runtimes are short, but still consumes a lot of power (W).  An example might be an electric coffeemaker.  
 +
 +It might run for only 5 minutes a day (1200w / 60 minutes in an hour * 5 minutes) = **100Wh**.  But during that run it is pulling ~118A (1200w / 0.85 inverter losses / 12v).  **So the entire system (batteries, wiring, inverter) has to be sized to that 118A load** thar runs only 5 minutes a day.  Do you love that Keurig enough to buy extra batteries, fatter wire, and a bigger inverter to run it?
 +
 +
 +
 +===== now what? =====
  
 +Now that we assessed our daily power and max current requirements we can think about
 + 
 +  * assessing our [[12v:bank-sizing|power storage needs]]
 +  * and [[electrical:12v:power_mix|power generation options]] ([[electrical:solar:sizing|solar]], [[electrical:12v:alternator|alternator]], [[electrical:generator|generator]], [[electrical:shore_power|shore power]], etc)
electrical/12v/dailypowerrequirements.1665771303.txt.gz ยท Last modified: 2022/10/14 14:15 by frater_secessus

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