12V System

@Sam Asante These are Karl's designs but I will do my best to comment based on my years of engineering and aircraft experience.

The Volt/Amp meter appears to be there for a status display and to provide an easy check of system status so that is fine. I think any of the commercial displays out there that work in the correct voltage and amperage range will be suitable. That could be an automotive indicator or one of the battery minders I mentioned, that is up to you to decide. I can see by the diagram it does show the use of the shunt properly, you just have to be sure that the ground wire for all of the devices connected to the power supply passes through it so the current can be monitored. A hall effect sensor for the current makes it simple, the wire just has to pass through it and no actual connection is needed.

The fuses are there to protect the devices against a short that would cause a wiring meltdown so they are a good common sense feature. There are various fuse holders available which use the fuses that are common to the automotive world. You could get inline fuse holders to incorporate into the wiring harness but you could also buy a fuse block that accommodates multiple fuses in one location in a nice and organized form, that is really the better choice. The fuse block approach would keep all of the fuses together in an easy to access location, some even have LEDs that will come on if a fuse is blown so you will know right away if there is a problem. Just look for Automotive 12V Fuse Blocks (or Marine) and you will see that there are plenty of options available in size, features and price.

The only other item I will comment on is that Karl has chosen to place the fuses in the ground line while I have typically seen them in the power line. I believe either way is acceptable and I am sure there are reasons why both are used. That just seems worth mentioning as the fuseblacks usually list features and show diagrams of typical applications for being used with the power lines but there is nothing that says you cannot use them the other way, a fuse does not care and neither will the fuse block. The only exception would be if you select a fuse block with the LED feature. That might mix up their leads between + and - and cause them to not work. Electrical Engineering is not my speciality but I do believe that is correct.

I hope that all of that gets you moving in the right direction and nothing I have said is inaccurate.

@Sam Asante Just to help out, I looked at what Amazon has in the way of fuse blocks and found this one which might be the simplest to use. It has the + and - busses connected at each end then a + and - connection for each load on the system. Nice and simple and its 6 fuse capacity will match well to the diagram (they also make different sizes). Most others would have you place an IN and OUT wire for each fuse with the - (or + as shown in Karls diagram) being connected separately so more wiring for the same result.

https://smile.amazon.com/Electop-Negative-Waterproof-Protection-Automotive/dp/B0838TZ2Z2/ref=pd_bxgy_1/141-2854456-8797102?pd_rd_w=1qP85&pf_rd_p=c64372fa-c41c-422e-990d-9e034f73989b&pf_rd_r=2HEB4CKHZ23MFW83MQVM&pd_rd_r=1b926716-4293-488a-b0a9-a3000467f07e&pd_rd_wg=Nqz5h&pd_rd_i=B0838TZ2Z2&psc=1

@Sarah Ashmore thanks a million!!!! really appreciate you taking the time to explain! I have no aviation background what so ever. the members are very helpful! will order these parts and continue the build!