Building a Portable Power Source for Camping/Festivals

Himselfe

I'm looking at the possibility of building my own portable power source for camping.

We do a lot of camping (trailer tent) and attend quite a few festivals from March through to October every year. We like our comforts so we tend to go to sites where we can hook up to the electric and have a few sockets in the tent, which can limit where we can go. At festivals its basically just a few power banks charged before we go to keep the phones topped up.

I had thought about just buying an off the shelf version like this:

https://solarpowersupply.ie/portable-power-stations/ecoflow-delta-2-power-station-eu-version?gad_source=1&gclid=CjwKCAiA7t6sBhAiEiwAsaieYtMjacu5hpx-HcIUrdFjNBCuicT76iNxJTsA_4lmYGZFB2EqMsKxRRoCjbYQAvD_BwE

but having had a conversation on another thread about DIY home battery setup it got me thinking about doing it myself. I'd like to build something compact and portable like this that can be charged both from solar and mains, has a couple of plug sockets for charging a laptop, lights, possibly a little heater etc., and has some USB outputs for mobile device charging. There are plenty of online videos about building something permanent and non portable for a campervan or simple setups that have just a basic power output for charging a phone etc. so I'd have to put together some sort of hybrid based off the videos.

https://www.instructables.com/DIY-Solar-Power-Pack/

https://www.youtube.com/watch?v=en-0OwEYAHQ&t=504s

Does anyone have any experience of building something similar or thoughts/tips on how best to achieve this? I'm thinking it could be less expensive to build one myself and potentially more reliable/flexible in terms of the battery capacity and outputs I could add in (not to mention more fun!). It seems most of the tutorials online use acid

Posting here in renewable energies as I thought its more appropriate than a camping thread.