Samsonite801
Solar Wizard
- Joined
- Oct 15, 2020
- Messages
- 2,994
I figure 12 hours of night use and a couple in the morning is a long time to wait before a south and west array start producing. My refrigerator doesn't work at night so it has to recover first thing in the morning. I'm about as close as you can get to using power directly from the panels. While not a typical day, refrigerator has recovered, hot water is up to 60C by 10am when I start the dishwasher (heating element runs from array DC) and have done three loads of laundry (direct from array power with hot water from PV) by noon with battery fully charged. It has to be a good day for laundry and started in the morning because we line dry. East facing array (1/3 of total panels) in my location produces more power than the rest of the system.
It is always site dependent and based on lifestyle. We don't have commitments like work which prevent us from doing things when the sun is shining. Dishwasher has a start delay feature making it easy to run when we are away, and the hot water gets up to temperature. Remarkably low battery requirements when you get away from the I want it now mentality. On a nice day I get nearly full rated power from the east array for several hours. South facing panels is just a dated way of thinking from when panels were expensive and batteries were cheap.
If you're like the instrumentation/analytics type of person, get yourself a battery monitor (shunt) for better visibility into the system).. In my example I use the Victron BMV-712 battery monitor, it allows to see amps, volts, watts, in-out of the gateway (the battery), and accurate SoC.
Just think of the battery as a big storage bucket, solar trying to dump into it as much as it can (when battery is low), and loads are trying to drain the bucket.
With a battery monitor, you start to get a natural feel for how the power is flowing into, out of, or skimming across the bucket (once it gets full). When the battery is full, and not many loads running, the charger (solar MPPT) ramps down and relaxes from full output state (wasted Sun).
For example, I find that if my goal is to try and keep my power at exactly 100% (once I get there), and a cloud rolls over a little bit (starts to affect production), say I decide to turn off my AC in the RV to conserve my 100%, I am now only wasting more Sun.
If my AC draws 2000w, and I leave it on instead, the cloud cover may reduce my output a bit, and maybe I'm only running a -400w deficit, it still makes sense to just leave the AC on and let it eat that 400w deficit into the battery, because I'm still getting 1600w from the Sun (not waste it, have more AC)...
Then maybe if it gets down to 95% battery (maybe is early evening and trying to keep more battery for the nighttime), I can turn off the AC then, and it will be trying to get full solar as it can from the panels to try and fill the bucket (charge the battery at full power again).
This is all more apparent on undersized system where you are trying to get all the solar you can, obviously if you have way more power than you may ever use, then one doesn't tend to worry about it or be as mindful about the power consumption, or the times of day you do various power-hungry tasks.
It's basically same like budgeting money in my eyes. The solar is like your income, the battery is like your bank account (up to the FDIC limit), the loads are like your expenditures..
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