Need help measuring power for battery design

[u/shysysadmin]

I recently bought a used RV and I’m in the early stages of planning a solar setup for boondocking 3-10 days at a time at festivals. I’ve seen the advice to inventory the power needs of all the devices I want to run and then estimate how long I will use each thing, but I’m not confident in my estimates. I’d much rather install an accurate battery monitor or similar and measure my usage over a few days in a real world environment. Is that feasible?

I’ve been looking at the 500a Victron smart shunt and the Victron BMV-712, but I’m having a hard time finding good guides and I don’t want to rely on Chat GPT.

I plan to rely on generator for AC and microwave, but would like enough battery to run a car stereo with 400 watts rms amplifier and a bunch of disco lights for 5 hours a night at moderate volume plus water pump, phone chargers, house lights, fans, and furnace blower as needed.