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electrical:solar:sizing [2021/06/21 14:08] frater_secessus [your daily power needs] |
electrical:solar:sizing [2022/01/15 03:10] princess_fluffypants [voltage] |
- whether or not you have access to other forms of charging: [[electrical:shore_power|shore power]], [[electrical:12v:alternator|alternator]], [[electrical:generator|generator]] | - whether or not you have access to other forms of charging: [[electrical:shore_power|shore power]], [[electrical:12v:alternator|alternator]], [[electrical:generator|generator]] |
- the kind of [[electrical:12v:deep_cycle_battery|battery chemistry]] - some((lithium, for example)) charge more efficiently than others | - the kind of [[electrical:12v:deep_cycle_battery|battery chemistry]] - some((lithium, for example)) charge more efficiently than others |
- These factors will tell you size of the system needed. If the system you need will not physically fit on/in your vehicle, you will have to take [[electrical:solar:sizing#maxxed_system|a different approach]]. | - the kind of camping you do. Full-timers will need more robust systems. Weekenders can [[https://mouse.mousetrap.net/blog/2020/07/04/agm-for-weekenders/|"get by" then recharge batteries fully at home]]. |
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| These factors will dictate the system capactity you will need. If the system you need will not physically fit on/in your vehicle, you will have to take [[electrical:solar:sizing#maxxed_system|a different approach]]. |
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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. Charging at lesser rates may result in not getting fully charged each day. Charging at greater rates may result in increased outgassing and the need for a lengthier Absorption stage. | 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. Charging at lesser rates may result in not getting fully charged each day. Charging at greater rates may result in increased outgassing and the need for a lengthier Absorption stage. |
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| === reserve === |
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| | **total**| 91| |
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| | Minimum battery bank((except lithium))| 182| |
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| and that's just to get through a 24hr period **with good sun**. If you want to get through a day (or more) of terrible solar yield (rain, snow, fog) it requires even more battery capacity (//reserve//), money, and cargo capacity. These numbers are both very rough but will illustrate the pattern: |
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| | | **Rated Ah**| **cost (flooded)**| **cost (AGM)**| **weight in lbs**| |
| | **Minimum battery bank((except lithium)) |
| 0 days of reserve**| 182| $182.00| $364.00| 91| |
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| | **1 day of reserve**| 364| $364.00| $728.00| 182| |
| | **2 days of reserve**| 546| $546.00| $1,092.00| 273| |
| | **3 days of reserve**| 728| $728.00| $1,456.00| 364| |
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==== charging efficiency ==== | ==== charging efficiency ==== |
Lithium batteries have very high charging efficiency, so 50A consumed will take ~50A to recharge. | Lithium batteries have very high charging efficiency, so 50A consumed will take ~50A to recharge. |
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==== voltage ==== | ==== Voltage ==== |
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Most camper solar installs run at [[electrical:12v:electrical_notation|nominal]] [[electrical:12v:intro|12v]]. Because of this most accessories are 12v. | Most camper solar installs run at [[electrical:12v:electrical_notation|nominal]] [[electrical:12v:intro|12v]]. Because of this most accessories are 12v. |
===== solar panel array ===== | ===== solar panel array ===== |
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Pick a solar panel array output on battery bank capacity. A common **rule of thumb for matching panels to battery bank** is that there should be 1-2 panel watts per amp-hour of nominal bank capacity. | Pick a solar panel array output on battery bank capacity. A common **rule of thumb for matching panels to battery bank** is that there should be **at least** 1 panel watt per amp-hour of nominal bank capacity. |
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> "...the person draining their batteries to the 50% range regularly would do much better with a 2 watts to 1Ah ratio, or even 3 to 1." -- SternWake((http://www.cheaprvliving.com/forums/Thread-How-much-solar-do-I-need?pid=278438#pid278438)) | > "...the person draining their batteries to the 50% range regularly would do much better with a 2 watts to 1Ah ratio, or even 3 to 1." -- SternWake((http://www.cheaprvliving.com/forums/Thread-How-much-solar-do-I-need?pid=278438#pid278438)) |
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' output plus a safety margin, unless you are [[electrical:solar:overpaneling|overpaneling]] on purpose. | - controller rating should be the panels' output plus a safety margin, unless you are [[electrical:solar:overpaneling|overpaneling]] an [[electrical:solar:charge_controller#mppt|MPPT controller]] on purpose. |
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===== augmenting solar ===== | ===== augmenting solar ===== |