First time DIY solar project

[ClassicCrazy]

If starting over , getting a kit from Northern Arizona Wind Sun may be a good option for you.
They use good components and everything would be matched for the size system it is.
https://www.solar-electric.com/residential/solar-panel-system-kits.html

Usually in designing a solar system the process would be,
Figure out your loads and energy usage
Determine how much battery storage you would want to carry you through on cloudy days
Determine your site conditions and how far your solar panels would be from controller/battery location
Get appropriate amount of solar panels to be able to charge batteries
Figure out voltage drop and wire sizing needed to bring power from solar panels to batteries.
Also in the above equation would be picking out appropriate size inverter to run loads and if it will be an inverter charger capable of charging batteries from generator.

These days for anything but the most basic system most people  put panels in series to get higher DC voltage to decrease wire size and voltage drop into the house .
Then you use an mppt controller to lower that input voltage to battery voltage.
The inverter type needs to be based on the battery voltage used such as 12,24, 48v etc.

But also these days there are  options for DIY such as the Midnite DIY combination controller/inverters all in one units. Plug the panels into that with some fuses or breakers on input as required,, and then use something like the available lithium 48v server rack batteries on the market .  So you put PV in, connect to battery, run AC output power out. 

That is overview  in a nutshell.

If you don't get something like the kits from NA wind sun where they will probably provide support, you are probably better off trying to find an experienced installer if you don't have the time to learn  and do the safe proper installation ( that won't catch on fire ). You absolutely have to understand basics of wiring and proper fusing / breakers for any home built system.

You may also want to look up Signature Solar to see if they have prebuilt or designed kits since they sell both batteries and controllers. Some of their controllers are very similar to Midnite DIY so you will get the idea and can decide which company you will want to go with and get support from.

Larry

[Robin]

I am not aware of a simple comprehensive guide to how to design a system? You are in a good place to learn here though. There are plenty of experienced people that will give you sound advice.
I never go to youtube for advice on solar systems. 99% of the systems there are poorly done and not per NEC code. I do go there for information on how not to do things.
The fact that you do not have any MidNite equipment is no big deal. You will get good advice here.
So, did you end up with four 12V batteries or 6V? 6V would have been the correct choice. Trojan steered you wrong. If you have 4 12V batteries they will do for a while. They will not last long and even if you had 6V batteries that bank is very small.
IDo not connect Harbor freight batteries in the same system as the Trojans. That will just insure that all your batteries wear out sooner than they should.
I love Harbor freight, but they have no good products for your solar system. Battery cables will be too small. Can't remember what else you bought there, but it is not up to the caliber of your inverter and charge controller. Schneider makes good equipment.
Do you have over current protection on your system? I don't recall hearing about any of that?
Battery breakers are important. If the inverter or charge controller fail you could burn your house down. You must have adequate battery cables and breakers.
Good luck and feel free to use this forum to learn.