Hello!
1. If the cell phone battery is removable, buy a few extra batteries as a backup or purchase a "mobile power supply".
2. If the mobile phone battery cannot be removed, it is recommended to purchase a "mobile power supply" (also called: power bank, battery bank) as a backup, with a capacity of several thousand milliamps. to tens of thousands, or even 1-2 10,000 mA, consider purchasing a large capacity one in the wild. Mobile power supplies are generally equipped with LED lights and can also be used with flashlights, which are very practical especially in the great outdoors. Equipped with a variety of charging connectors, all mobile phones on the market can be charged. If you stay outdoors for a long time, you can carry a few extra large-capacity mobile power supplies.
II hope it can help you and I hope you adopt it!