Portable GPS Trackers will allow you to track people, cars and assets. These units can work for several weeks on a single charge.
These units offer the most flexibility. It is possible to carry them in a pocket, purse, backpack. You can also place inside vehicles. Another option is under cars or trucks with a magnetic case that is sold separately.
On the tracking app or website, you can view the battery level or even get an alert when the battery is low. This way you will know for certain when it is time to charge the unit again.