Wiring diagram - Find my mistakes!

I cannot post links or pictues, quite hard to explain a wiring diagram in words...

Read the forum on picture posting.

Open this link and scroll down to easy photo posting to see how to show your pictures.

What is the reason for the DC-DC charger? Doesn't the alternator keep the chassis battery charged? Plus with the 2 batteries in parallel the voltage from solar should keep them both charged. But normally there will be an automatic connect of the 2 banks only when the engine is running, otherwise disconnected so that the chassis battery is always charged so that you can start and go.

Your solar has both 10 and 6 ga wires, should be the same. Wire size is based on the amps and series voltage. My panels for example are 9A and 36 Vmp with 62' of 10 ga wire and about 2% voltage loss. No need for the fuses on the MPPT input as the panels will not be damaged with a short. See the Imp panel spec. Use you panel specs, wire length and online wire calculator to determine voltage loss. 3% or less would be good. To be clear your panel wiring is not carrying 40A, but a lot less due to the higher voltage, MPPT converts the higher panel voltage power to lower voltage with more amps on the output. Posting panel specs will help.

The most critical wiring is from the MPPT output to the house battery and from the house battery to the inverter. Wires should be as short as possible and sized to handle the higher amp loads to minimize wiring voltage loss.

You show the red AC wire grounded which is OK if it's the neutral. In the US neither would be grounded and there would be a separate ground wire.

Hope this helps.

Is China shore voltage 220 Volts or 120 Volts?

I believe China is 220V 50Hz.

Thanks for your contribution guys and please forgive my inexperience regarding image posting, will do that next time.

Is China shore voltage 220 Volts or 120 Volts?

It's 220v.

@CA Traveler: Thanks a lot, your answer is super helpful!

What is the reason for the DC-DC charger?

The chassis/starter battery is lead acid, the house battery is Lithium, so I read the safe only way to charge the second from the first is to use a DC-DC charger instead of relays so that it can keep a steady 14.6v charge.

Your solar has both 10 and 6 ga wires, should be the same.

You've hit a painful spot! I am building this van in the countryside with limited tools and shops, everthing must be ordered online and it takes days to arrive, so I asked the solan panel company to wire the panels for me to save time. I asked for 10 AWG cables but later I thought I had made a mistake because I only calculated half the wire lenght so, despite myself, I thought I had to rewire the "long sides" with 6 AWG cables. But from your reply I understand my first calculation (10 AWG) was probably correct, right?

Here are the panel specs of each panel (translated from Chinese, no instruction manuals, only a minimal label on the back):
Peak power: 300W
Open circuit voltage: 22.5V
Short circuit current: 16. 6A
Working voltage: 18V
Working current: 15.5A

Total length of the cables is 3+3=6m (20ft). As they are in a series, the max current going through them is 16.6A?

Wires should be as short as possible

From the MPPT to the battery there will be 40.8A and max 1ft distance, so I chose 6 AWG. From the inverter (1000w) to the battery I expect 100-120A max so 2 AWG should be enough but I wanted to cover for unexpected peaks up to 2000w if the CB fails so I chose 2/0 AWG. Useless?

the red AC wire grounded

My bad, I meant to connect the ground to the black cable in the diagram.

Thanks again!

when you get done, only turn one item on at a time.

10 ga wire on the panels results in a 1% voltage drop to the MPPT, very acceptable. Max current is 16.6A and 15.5A requires full sun which won't happen often.

House battery should not exceed 200A, so you could reduce CB size.