“No cell coverage” draining battery fast on iPhone SE even after battery replacement

cozycruiser wrote:

I discovered that "no cell coverage" is responsible for some of the drain. I don't have much cell signal at my rural house, so I'm assuming that the phone is wasting energy by unsuccessfully searching for a signal.

Correct observation. All cell phones use the minimum power necessary to maintain a connection, but that minimum depends on signal strength. A 1 bar signal uses 10 times as much energy as a 4 bar signal, so if you are on a 1 bar call it will eat battery very quickly.

If you are not on a call the phone will periodically handshake with the network; again, if it is low signal strength this will use much more power, but, as it is a short exchange, the handshake won’t use that much power.

The worst possible condition is if the phone goes in and out of communication with the network. Every time the phone loses connection it sends “where are you” signals every few seconds; this uses a lot of energy; if there is no answer in several minutes it stops trying, and then tries again every few minutes.

If you have a reliable weak signal it should not hurt to leave the cellular radio on, but if it goes in and out it is better to turn on Airplane Mode, then turn on Wi-Fi and Bluetooth (as already mentioned). And also enable Wi-Fi calling if it is available from your carrier, so you are not dependent on the cellular network.

My experience is that very low cell coverage can also drain your battery. Put the phone in Airplane mode and turn WiFi and BT back on. Those choices should be retained.

However, if you're using SMS messaging, you either need to keep cellular on or have WiFi calling enabled.

Make a call with Wi-Fi Calling - Apple Support

If you have any signal at home then it will not be searching. Leave it on.

it should not be more than about 5% typically, but remember that is 5% of the battery used that day, not necessarily 5% of the full battery capacity.