Hi Chagrin,
Thanks a lot for your very clear explanation and taking the time to write down the whole process. I'm going to have to bookmark your answer for future projects!
I guess I'm going to need a bigger battery for this project as 4h of autonomy won't be enough. I was hoping to find a way to get 5 days of autonomy, that was a bit naive of me. I'm not even sure that will be possible.
I've learned something today and I will be going to bed less stupid 
Cheers!