by flboy » Wed Jun 24, 2020 2:05 pm
Hi.. I think I understand what you are saying now... and you are correct if the panels cannot supply all the needs of the Air Conditioner while running and the battery is discharging. It is true that the battery when it is charging... it may not use all the power you might have available to charge depending on it state of charge, temperature, etc..
I am not going to go through all the math because it can be misleading without all the variables applied when actual data is taken. At best, it good for making purchase decisions and trade offs for designing your system.
Note also. that I have 225 aH available for use. You can only take lead acid batteries down to 50% so 450aH are not available to use (I know I said 425aH earlier. It is actually 450aH) so I would say I used 50% of the battery power... not the 450aH you assumed.. but in any case, yes, there are all sorts of inefficiencies. For one, three of the panels had partial shade for 2 of the 3 hours taking me down to 500W that was also under partly cloudy conditions. In those circumstances I was only onboarding 29A from the panels.. which is a real life scenario.
My point is that if you want to run an AC reliably and for extended periods night and day, make sure you have a generator or else you will need more solar panels and batteries than you will want to carry.
For my intended purpose of running for a few hours during the day at stops or for the pet while I am out, and starting with a full charge, this works and is a great compromise of cost, capacity and functionality.
If this was a permanent structure and I had the money, I'd add alot more panels and storage, but even at that with the cheap cost of electricity, it likely would never pay back because things will break about the time you recover costs if ever.
You have to be realistic on what you can do. My answer to your question is the same. The rate your battery can take a charge does not factor into the equation while AC is running. When it stops running, that does affect battery recovery time.. but it is on a curve depending in how far you are discharged. So, if your panels can handle the full need of the compressor, the battery charge rate again does not matter. It starts to play into the equation when panels cannot keep up alone and the battery is supplementing. In that case if I have 800W or 67A trying to charge the bank which is at 80%or 90%, I may only be using 50A or.much less of the 67 available under ideal conditions. I have seen my system pump in over 55A when I was discharged well and the sun conditions were good. I have never seen full capacity (marketing numbers).
Back again to, a lot of variables.. so carry a generator too for the best of both worlds. I hope this helps and does not confuse.. best wishes.
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