Is my basic understanding of the theory correct in this image?

[Lord Doa]

I realized I didn't have a full understanding of the theory behind solar so I'm trying to get that locked down. My idea being the more I understand how the system works the better I'll be able to troubleshoot and optimize it.

First off, are my following assumptions correct?
Solar panels - Generate power (DC) from the sun
Generator - Generate power (AC) from fuel source
Solar MPPT - "Traffic cop" for incoming DC power from solar panels
AC Charge Controller - "Traffic cop" for incoming AC power from generator
Inverter - Converts DC power to AC
12v Converter - Convert 48v down to 12v
Batteries - Store power for use later

And then is this rudimentary design correct? I just noticed I left out the connections to AC & DC appliances, but let's imagine they're there. This design assumes building from components not an AIO solution.

One thing I can't get my head wrapped around is how the incoming power knows to go to the batteries or the devices. Is it a path of least resistance thing so if no appliances require energy it gets dumped to the battery?

Another thing I didn't know is whether I should put a fuse between the Positive Bus and Converter and Inverter. My mind is telling me that I will need to if the devices don't have overvoltage protection, right?

ne

 

[Mattb4]

Both your solar panels and fossil fueled generator generate power when loaded. It is a important thing to keep in mind that the panels will sit in the sun and do nothing and the generator will burn fuel keeping spinning but no power is delivered anywhere if a circuit to a load is not made.

The SCC job is to charge a battery. It does this by energizing a DC bus at a particular voltage to which your battery and inverter is connected to. Your battery acts as a load when it is less than fully charged. Since this load drops the common DC bus voltage the SCC acts to bring it back up and this increases charge current. Your inverter can also demand power from the DC bus. When it does it has prority based on near zero resitance.

But once the battery voltage rises to the SCC voltage setting for CC it switches to CV and holds the voltage constant by reducing the current down to just enough to do so. Once the SCC decides your battery is fully charged it shuts down demanding power from the solar panels. You inverter however if it still needs power it begins to draw from the battery and the DC common voltage drops as the battery capacity drops. Eventullay teh SCC begins the cycle over again.

AC to DC chargers are similar to a SCC in operation. Common name is battery charger.

Converters take AC power and make DC power.

Inverters take DC power and make AC power.

DC to DC voltage changers take a lower or higher DC voltage and output a lower or higher DC voltage.

 

[mikefitz]

The fuses shown prevent excess current flow. The 'master' fuse at the battery protects the cable run and the positive buss bar. The fuse in the run to the solar controller and the fuse in the cable run to the AC controller prorect against excess over current fron the bzttery if faults occur in the cable or the controllers. These fuses need to be positioned as near as possible to the buss bar, or to use a distribution buss bar/ fuse holder.
The incoming power will flow to either the inverter load alone if the battery is fully charged, or shared between battery charging and inverter if the battery is low.
If the incoming power is lower than inverter demand, the battery will make up the shortfall.

If there is no inverter demand, battery charging will take place untill the battery is full. At this point battery volts are the same as charger volts.

Current will only flow from a high voltage point to a lower voltage point. If the voltage at two points is the same there is no current flow .

 

[E. Cho]

.....
One thing I can't get my head wrapped around is how the incoming power knows to go to the batteries or the devices. Is it a path of least resistance thing so if no appliances require energy it gets dumped to the battery? ....

As far as I know, Yes, that diagram looks better as is your description / understanding.

From my readings on these forums: The incoming power is only incoming IF there is a load requiring it. Otherwise it just sits there in the solar panels doing nothing. It's been compared to the AC power in your house, it's there doing nothing until a light or appliance needs it, which then draws only the power that is required vs all the potential power in the wiring.

So the appliance or load, PULLS in the power it needs, through the battery, which supplies the power until the load / power draw is removed or shut off and then the battery pulls in the power it requires to recharge. The power also only flows one way, which is to the load / appliance that requires it and always from the battery first, even if there is enough solar and the battery is full, although I understand there are some solar charge controllers or settings that can provide power directly if the battery is full. But generally, the power is always pulled from or through the battery first.