XPost: alt.home.repair, sci.electronics.repair   
   From: bowman@montana.com   
      
   On Sun, 17 Nov 2024 08:42:22 -0700, Charlie wrote:   
      
   > I'm trying to size the solar panel, where you're helping a lot, as I   
   > just realized only when I did the math above that I may need something   
   > like a 50 Watt panel for the smaller pump to run it real time.   
   >   
   > But don't I need a smaller panel if it's running off the battery?   
      
   There is no magic. The battery is a storage device. If you take 250 watt-   
   hours out, you need to put 250 watt-hours in, or more like 300 for   
   inefficiencies. You have to figure out how many hours of dependable sun   
   light you have, allowing for overcast days.   
      
   Think of a battery like a checking account. It doesn't matter when you   
   deposit money or when the checks clear as long as there is as much or more   
   going in than out. Erring on the high side is better. Say you have three   
   or four overcast days where you're not putting much in. That will   
   discharge the battery.   
      
   Car batteries are designed mostly for cranking amps and do not like being   
   deeply discharged and recharged. RV or 'deep-cycle' batteries are designed   
   for that use.   
      
   https://en.wikipedia.org/wiki/Deep-cycle_battery   
      
   RV batteries are a compromise:   
      
   https://www.interstatebatteries.com/recreation-vehicles/rv-batteries/deep-   
   cycle   
      
   The gold standard for solar systems are golf cart or forklift batteries.   
   They are heavy, expensive, and what you find locally may be 6V so you need   
   two.   
      
   I'm leaving out lithium ion batteries, given your shoestring budget.   
      
   --- SoupGate-DOS v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)