Please help me. Advanced setup with Model S battery, All in one MPP, and 50 amp shore inlet circuitry

[Robbie]

So I'm currently in the middle of an off grid vintage travel trailer renovation and have been actively trying to learn electrical basics in my "down time." I've read William's book, have been reading forums, and absorbing what I can infer from videos and diagrams of similar setups to what I'm trying to achieve.


I'm starting to install my electrical components for my solar system and would really appreciate any advice or feedback so I'm not just entirely winging it. I have a Model S battery, all in one MPP PIP2424LV-MSD inverter, 400w of solar to start with (expanding to at least 800w), and a 50 amp inlet for shore power.

The 50 amp has two 120v leads so only one can go to the MPP. The other I was planning on running to an AC breaker box for outlets meant only for when shore is available. I came across this diagram for an article where a 30 amp breaker in a small sub panel was used for the 120v lead that feeds into the inverter.
Would it be correct to use 6 awg from the inlet to the 30amp sub panel breaker, and then 8 awg to MPP AC in? Or can I use 6 awg on an mpp?
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On the AC out I am planning to run back to the main AC breaker box, as depicted in the attached diagram with two leads feeding different circuits from the same box.
The diagram shows a 50 amp main breaker coming from the inverter, so should I use 6AWG on the AC OUT to the main breaker box?
Honestly this part is really confusing to me so if anyone has any advice on a simple way for me to approach figuring this out please share!
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I don't want to make this post too involved so my last things I am curious about sizing correctly are for my 12V system.
I am planning on getting a 24V>12V 100amp step down converter to feed my 100amp capacity 12v fuse block. Is that the right size or should it be higher or does it not even need to be that much? I doubt I'll use all 100amps of 12v, but I'd like the option to add on nonetheless.
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I also got a victron 220amp battery protect, as well as the BMS, and other peripherals Will suggests for a Model S setup, but I'm not sure what size bolt on fuse I should use on the battery powering a 120v breaker panel and 12v fuse block. Should I stick with the recommended 175amp bolt on fuse? This MPP is 2400w so should I increase this to 200amps because of this or more because of the large step down converter?

Thanks for any help you can offer!
Yes, I realize I'm in slightly over my head experience wise. But this subject is finally making more sense to me, so hopefully I'm almost there and not just further away than I can even imagine on this... ?


I'm definitely a practice makes perfect learner so I am totally exercising caution with respect to this install.

 

[Ampster]

Maybe a diagram would clarify. I stopped when I read you were going to run one leg of your shore power to your inverter. Or maybe you could take one major component at a time so that once you get that right you don't have to go back and correct your initial post so everyone doesn't jump on you. One place would the AC side of things or the DC side. You decide.

 

[Robbie]

True. Good points. I'll remake this post approaching one thing at a time.

 

[Forbisher]

If you are winging it a Tesla battery without a BMS is not a good idea. If you overcharge the Tesla battery bad things can happen.

 

[Robbie]

Okay, well I wasn't counting on a 60 minute limit to edit posts.
I'm sorry I didn't edit it in time.
This is the diagram I was referring to regarding the 30amp sub panel breaker.

I'm really trying to start with; How do I connect a 50 amp inlets wires safely to an MPP inverter?
If 8 awg is the normal size wire for the MPP AC in and out, and 6 awg for the 50 amp wires, then wouldn't a subpanel make sense?

 

[Ampster]

I did not understand that your inverter had an AC in port. That must mean it can pass Leg One through the inverter to the Leg One side of the panel. Each side of the 50 Amp plug can carry 50 Amps but the smaller breaker on that leg will protect the inverter which may only be able to carry 30 Amps through its circuits. Notice that the main panel uses 50 Amp breakers so to be safe I would use the larger wire on both legs of the shore power. If that is not your panel configuration maybe you might want to size that breaker for 30 Amps to further protect the Inverter from larger circuit draws on that leg.

Presumably since it is also an inverter it will charge your battery. Before you hook up the battery, in response to the comment from @MBR
you should double check that you have the correct voltage set for the charger part of the inverter. To be safe you should set it at something less than 4.0 volts per cell. There may be several places to do that including Absorb, Float and even possibly Equalize. Equalize should be off. Absorb time should be zero time until you are ready for more precise settings. Bulk current should be as low as possible until we get into the details of the battery, charging and the settings on a BMS.

 

[Robbie]

Thank you!
My inverter has a 40amp capacity for AC in and 25amp AC out. So I think a 30 amp breaker would be fine for the sub panel between the inlet and inverter.
It can only do 25amp AC out, so I'm not sure about what size breaker to use on the main breaker box that distributes the load to my AC outlets I intend to use for solar.
Would a 30 or 50amp breaker still work in the main panel or should I size that leg's breaker to match the 25amp output? (The other 120v leg that goes to the main breaker will still be on a 50amp breaker, though I suppose 30 amp for one leg would be sufficient as well?)