I set my phone aside in a faraday box for 4 days. No apps have unrestricted battery permission. The battery usage statistic chart shows 84% of it was used on Mobile Network. I don't even have a SIM card.
I guess let this be a reminder to put it into airplane mode if you are using a faraday cage lol
That being said, why is the phone searching for mobile networks at all if it doesn't even have SIM card?