Why a analog INA169 ? Is that because the distance is too far for the I2C bus or is there no 60V I2C version ?
You can step down to 5V and power a Arduino via its 5V pin. There is a risk that current can flow into the USB port of a computer.
A problem could be the GND.
With high currents through ground wires, a good common ground is hard to make. If you do something wrong than many amps might try to go through the Arduino board.
When the ground current can take two routes, the ground current can decide to use a smaller wire and ignore a strong thick wire. For example when the small wire is inductive coupled with the positive power wire. For higher frequencies it is often worse. Current spikes are higher frequencies. You have indeed high frequencies in your 12V DC system.
I would add a few good old fuses, so a shortcut near the Arduino will not damage the rest.
How do you display the numbers ? A LCD display is not durable in a camper (sun, heat, vibrations).
INA226 is 36volt/16-bit bidirectional.
Breakout boards available.
INA219 is it's predecessor. 26volt/12-bit bidirectional.
INA3221 is three INA219 in one chip.
INA169 is high voltage, but uni. And needs the (10-bit) Arduino A/D.
You need two of them back2back for bidirectional.
Leo..
Why not just use 2 shunts one coming from battery to your load monitor everything and then one from your solar panel so you can monitor the charge going in
I’ve built one and made some changes and used an 16bit adc all credit goes to the author
Edit ignore the 2 shunt I’ve just looked at your picture more as I was looking on phone but the link still would give you some ideas, it uses The Peukert equation where you take more than 1 ampere out of the battery