If you’re like me the whole solar thing can be very mind boggling. I am NOT an expert. Let me hopefully help you understand what the solar setup and the charge controller does and why by adding an analogy:
Let’s imagine you have a 5 gallon water container with a spigot on it and you use that water for giving your pet water or other small things. When it gets low you fill it back up with a water hose that has a spray gun on the end and is connected to a limited supply water system that turns off at night and supplies water on a sliding scale during the day with noon being the peak time. You go over, turn on the water spigot and then you press on the spray gun to fill the water jug. It’s almost empty so you open ‘er up and let water surge into it and as it gets full you let off until the water level is where you want it. Then you turn off the water spigot until the next time. Weather will affect if your water supply system has water available or not.
So, in this analogy the water container is your battery (batteries), the spray gun and your hand controlling it is the controller, and the main water spigot at the source is the sun. The small water spigot on the water container is whatever you have connected to the battery(ies) that you need to use them for (as well as your inverter if you need to use 110 power). Please keep in mind that the larger your inverter is, the more power it takes to just run it alone so keep that in perspective to your needs.
When you use your batteries, they (of course) run down and you have a charge controller hooked up to them and to the charge controller the solar panel(s) are also hooked up. When the sun comes up in the morning and the solar panels kick in, the controller looks to see what shape your batteries are in (how depleted they are) and then it opens the “nozzle” all the way so it can fill them back up (charge them). The only problem is that the sun is not all the way up so it can only use what it has available. As the sun rises and the panels have more access to more solar energy the more of that energy can be passed on to the controller and the batteries. The controller will flood the batteries with as much power as it can and just like our analogy above, it’s pushing it in so fast that the battery meter will read much higher than it actually is (just like filling a bucket as fast as you can, you really don’t know how much you have until you slow down the flow and look). Mine will normally read 14.4 during the flooding process and then as it gets fully charged and the controller slows the flow of power to them they will read 13.4 (which is my benchmark – or full water container indicator).
My charge controller will then pass through power little by little as I use it but if I use more than it’s passing through then when it hits 12.8 or lower it will start pushing more power to get it back up to 13.4.
I don’t normally use more than my panels can keep up with except when the sun goes down and there’s no more power to get. So, the biggest key to solar power is battery management.
What if, in the above analogy, you were trying to water a garden? That 5 gallon container would never work. That’s what you have to figure out, are you watering a garden or a dog? How big is your dog? How big is your garden? You have to have some sort of an idea what you will be using your batteries for and how often before you can decide what size system you need. Only YOU can figure that out.
Are you watering a horse trough all at one time? (aka: a microwave) or are you on a drip system (aka: a 12v refrigerator)? Is the 5 gallon water container going to be enough to give you the water you need during the time when there is no water available? Batteries are not water containers which are endlessly refillable – if you continually deplete your batteries and then use them before they have had a chance to recharge, your batteries will not last a year – no matter what type you have. Get the right number of batteries you need for what you need them for (do you need a 5 gallon container, a 2 gallon or a 100 gallon?)
I hope this helps in some small way.