[Ian Comerford]

I guess the first thing is to test your charging system to understand whether the alternator is working. I think I recall running the engine at around 3k revs and checking to see if the battery is getting at least 13.6v.
I had some battery issues this year and bought one of these to attach to the battery Andre lately monitor it via an app. It has been really useful
https://www.amazon.co.uk/Battery-Monitor-Campervans-Compatible-bluetooth/dp/B08VHMJYXY/ref=sr_1_5?keywords=12v+battery+monitor&qid=1649862011&sr=8-5