Having a poor signal drains a lot more battery because the phone alters transmit power based on signal strength. Being in an area where you have NO signal should not drain it much.

Another thing that drains the battery is using the phone outdoors in daylight, if it has auto-brightness enabled. The screen is usually the…

Note, you can get Lithium based batteries in AA etc but these are not rechargeable, and are a different technology to Li-Ion rechargeable batteries, which have never been available in traditional sizes like AA.

You can get Lithium based AA batteries but these are not rechargeable, so a different technology to rechargeable Li-Ion.

No NiMH don’t have memory effect. Some, but not all NiCad did, but never NiMH or Li-Ion.