The navigation with a constant GPS connection uses a lot of energy, there is no way to change this. There are some tricks to make your battery last as long as possible if you are on a long Tour:
The display uses a lot of energy, so use it as little as possible. The voice navigation will make sure you don't need to check the map. On your Android device, you can additionally use the function “Wake up screen” that you find tapping the loudspeaker symbol in the running navigation
On your Android device you can turn off Wifi, so your mobile phone won't keep searching for it, deactivate mobile data, use only GSM or switch to flight mode entirely, so that only your GPS remains activated. This is not recommended and in part not possible for iOS devices - Apple also uses Wifi to determine your location.
Turn off synchronizing for unused services, so they won't keep updating
Using your phone and listening to music eats up energy as well, as does using other apps simultaneously
A Powerbank can be used to recharge your battery several times, and thus make sure you have enough battery until you reach the next plug.