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opinion:solar:sizing [2022/05/24 15:10]
frater_secessus [battery bank]
opinion:solar:sizing [2022/05/24 15:13]
frater_secessus [overall economics]
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 [[lifestyle:words_of_wisdom|Words of Wisdom]]:  "You have to build for winter, and figure out what to do with the extra electricity in summer." -- timselectric((https://diysolarforum.com/threads/less-than-perfect-off-grid-system.35869/post-450655)) [[lifestyle:words_of_wisdom|Words of Wisdom]]:  "You have to build for winter, and figure out what to do with the extra electricity in summer." -- timselectric((https://diysolarforum.com/threads/less-than-perfect-off-grid-system.35869/post-450655))
  
-====== solar sizing - the Big Picture ======+====== power system sizing - the Big Picture ======
  
 There are many [[electrical:solar:sizing#calculators|calculators where you can plug in the numbers]].  This page is a 35,000ft view of how choices affect what you will need.  There are many [[electrical:solar:sizing#calculators|calculators where you can plug in the numbers]].  This page is a 35,000ft view of how choices affect what you will need. 
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 In general, bigger systems (higher wattage panels, bigger controllers, bigger battery banks) cost less per-watt-harvested. In general, bigger systems (higher wattage panels, bigger controllers, bigger battery banks) cost less per-watt-harvested.
  
-Broadly speaking, lithium chemistries are most cost-effective when the camping experience is expected to last for many years and the batteries stored inside.((Note that it is false economy to pay for 10 years of battery cycling (as with lithium) if one is going to wreck it in 2 years)).  For shorter projects (traveling around the country for  ≤3 years) in an RV with exterior battery trays the standard T-105 style FLA bank((like 2x 6v Trojan T-105 batts in series for 12v)) may be more cost-effective.  For very short installations ( ≤1 year) marginal batteries found at walmart may be fine. I encourage people to do the //$/kWh math for the situation// rather than relying on the latest trends or loudest voices. Horses for courses.+
 ==== days of reserve ==== ==== days of reserve ====
  
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 Your **reserve requirements** will profoundly affect the size, complexity, and cost of the system.   Your **reserve requirements** will profoundly affect the size, complexity, and cost of the system.  
 Sizing for an overnight camping trip is easy;  sizing for a three day trip a challenge;  sizing for a long trip or full-time vandwelling is serious business.  See the bottom of this article for example configurations.  Sizing for an overnight camping trip is easy;  sizing for a three day trip a challenge;  sizing for a long trip or full-time vandwelling is serious business.  See the bottom of this article for example configurations. 
 +
 +===== battery bank =====
 +
 +Once you know your daily power and reserve requirements you can spec out a battery  bank.  The capacity and chemistry of the bank will drive much of the charging section below. 
 +
 +
 +Having an **undersized bank** means //running out of power// at night.  Sitting in the dark at night with no fan.  
 +
 +Having an **oversized lead bank** for your charging ability results in [[electrical:batterycide|battery murder]] and replacement.  Having an **oversized lithium bank** is $$$ and can strain the alternator if [[electrical:12v:b2b|a current-limiting isolator]] isn't used.
 +
 +IMO, with lead chemistries((flooded, agm, gel)) it is better to have an undersized bank you can charge //fully and consistently// rather than a bigger bank you cannot charge. 
 +
 +You will **need somewhat more Ah capacity**
 +
 +      * if you have undersized solar
 +      * you have lead-chemistry battery bank
 +
 +You will need **somewhat less Ah capacity**
 +
 +    * if you run loads in the daytime instead of at night
 +    * if you have [[electrical:solar:overpaneling|oversized solar]]
 +    * you have lithium-chemistry battery bank((can be ~0.62% the size of the lead bank, due to deeper [[electrical:depth_of_discharge|DoD]].))
  
  
opinion/solar/sizing.txt · Last modified: 2023/12/26 11:57 by frater_secessus