From my modest experience i have to say, that my Huawei P30 Lite lasts normally two days. Except i wake up to early, can´t sleep and read the international news. But then i stick it into the charger. In the past 5 years i never experienced a problem due to a lack of battery capacity. Only once i had a problem with the KAZAM Tornado 348 (2.000 mAh as much as i remember). I was on the Island of Losinj. I woke up, checked mails an news in my bed and went to the restaurant. There i surfed the news and went back home. But this was the day of the World Championships in Spearfishing, how i surprisingly noticed. The camera shot the KAZAM to its battery death, but i was still able to shoot about 50 pictures before.
More important IMHO would be, if the battery of the Carbon will be replacable without needing a so called expert. I did this with my Sonys and that was no rocket science.
I suggest thinking about this point, because the Carbon will be far to rare that normal Handy-Shops in Germany will have spare parts for it. So we would need to help ourselves or send the Carbon in, which will take a minimum of a week to get it back. Since i am living on the beautiful Island of Losinj, it´d took me even longer.
Those are my real problems, not the battery.