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electrical:solar:sizing [2020/01/19 19:44] frater_secessus [your reserve needs] |
electrical:solar:sizing [2023/06/16 12:29] frater_secessus [solar panel array] |
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- worst case scenario [[electrical: | - worst case scenario [[electrical: | ||
- | - worst case scenario sunlight, usually December in your geographical area due to shortest daylight hours, but also affected by tree canopies, mountains, "urban canyons", | + | - worst case scenario sunlight, usually December in your geographical area due to shortest daylight hours, but also affected by tree canopies, mountains, "urban canyons", |
- days of reserve (ie with no solar charging) you want | - days of reserve (ie with no solar charging) you want | ||
- whether or not you have access to other forms of charging: [[electrical: | - whether or not you have access to other forms of charging: [[electrical: | ||
- the kind of [[electrical: | - the kind of [[electrical: | ||
- | - These factors will tell you size of the system | + | - the kind of camping you do. Full-timers will need more robust systems. |
+ | |||
+ | These factors will dictate | ||
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Before you dig in, consider that it is far **easier and cheaper to [[electrical: | Before you dig in, consider that it is far **easier and cheaper to [[electrical: | ||
- | Power requirements are usually expressed in Amp-hours needed every day (Ah/ | + | Power requirements are usually expressed in Amp-hours needed every day (Ah/day), although thinking in Watt-hours (Wh) might be simpler less complicated. |
+ | |||
+ | There are two different kinds of loads ' | ||
==== how much power does stuff use? ==== | ==== how much power does stuff use? ==== | ||
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==== calculators ==== | ==== calculators ==== | ||
+ | * Unbound Solar [[https:// | ||
+ | * AltE [[https:// | ||
* [[https:// | * [[https:// | ||
* [[http:// | * [[http:// | ||
* [[http:// | * [[http:// | ||
+ | |||
+ | Also see [[https:// | ||
===== your reserve needs ===== | ===== your reserve needs ===== | ||
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A rule of thumb is flooded lead acid batteries in offgrid scenarios should be charged between C/10 and C/8. For a 200AH bank this would be 20A-25A. | A rule of thumb is flooded lead acid batteries in offgrid scenarios should be charged between C/10 and C/8. For a 200AH bank this would be 20A-25A. | ||
+ | === reserve === | ||
- | ==== voltage | + | |
+ | |||
+ | |||
+ | |||
+ | |||
+ | | **total**| | ||
+ | | | | | ||
+ | | Minimum battery bank((except lithium))| | ||
+ | |||
+ | |||
+ | and that's just to get through a 24hr period **with good sun**. | ||
+ | |||
+ | | | **Rated Ah**| **cost (flooded)**| | ||
+ | | **Minimum battery bank((except lithium)) | ||
+ | 0 days of reserve**| | ||
+ | | | | | | | | ||
+ | | **1 day of reserve**| | ||
+ | | **2 days of reserve**| | ||
+ | | **3 days of reserve**| | ||
+ | |||
+ | |||
+ | |||
+ | ==== charging efficiency ==== | ||
+ | |||
+ | Lead batteries take something like ~13% more amps to charge from 50% DoD than were consumed. | ||
+ | |||
+ | |||
+ | Lithium batteries have very high charging efficiency, so 50A consumed will take ~50A to recharge. | ||
+ | |||
+ | ==== Voltage | ||
Most camper solar installs run at [[electrical: | Most camper solar installs run at [[electrical: | ||
+ | |||
+ | Some installations utilize 24v electrical systems. This is common in boats, and occasionally some very large commercial RVs. The common theme of an advantage to 24v is that you're using half the amperage to transfer the same amount of power, which can result in cheaper components | ||
You may want to consider running a 24v system if: | You may want to consider running a 24v system if: | ||
- | * your panels are rated at 600w or higher - Ohm's law tells us that 600w / 12v = 50A but 600w / 24v = 25A. | + | * You have a //lot// of solar, like 600w or more. |
- | * the run from panels to charge | + | * Ohm's law tells us that 600w / 12v = 50A but 600w / 24v = 25A. |
- | * you will be using inverters heavily | + | * You will be using inverters heavily |
+ | * Inversion | ||
+ | * You have large, power-hungry appliances that can run natively off of 24v | ||
+ | * Some [[food: | ||
+ | * You have a lot of long, large cable runs | ||
+ | * 24v doesn' | ||
+ | * A 24v system can use a much smaller/ | ||
- | There are downsides to 24v, however. | + | There are downsides to 24v, however. |
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===== solar panel array ===== | ===== solar panel array ===== | ||
- | Pick a solar panel array output on battery bank capacity. | + | Pick a solar panel array output on daily power requirements and |
> " | > " | ||
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* deep cycling with [[electrical: | * deep cycling with [[electrical: | ||
* **2:1** - deep cycling and charging from solar only | * **2:1** - deep cycling and charging from solar only | ||
- | * **3:1** - deep cycling and charging from solar only in areas with low insolation like the Pacific Northwest (PNW) | + | * **3:1** - deep cycling and charging from solar only in [[opinion: |
A **crude rule of thumb for panel output per day** is a horizontally mounted panel on a sunny day will generate Ah (amp hours) roughly equal to Rated Wattage / 3.((http:// | A **crude rule of thumb for panel output per day** is a horizontally mounted panel on a sunny day will generate Ah (amp hours) roughly equal to Rated Wattage / 3.((http:// | ||
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There are two general rules: | There are two general rules: | ||
- voltage from panels must not exceed controller voltage, ever. | - voltage from panels must not exceed controller voltage, ever. | ||
- | - controller rating should be the panels' | + | - controller rating should be the panels' |
===== augmenting solar ===== | ===== augmenting solar ===== |