Battery efficient GPS/Sat Nav app I'm looking for a battery efficient satellite navigation app for use on my bike. The problem is that GPS apps are a huge drain on the battery. My iPhone 6S lasts just under 3 hours when running Google Maps.

Years ago, I remember some app that had the feature of dimming the screen in between navigation instructions. I've checked Apple Maps, Google Maps and Waze and these do not appear to have the feature I describe. 

Does anyone know of a good GPS/Sat Nav app that is gentle on the battery?
The solution I took in the end involves turning off the screen when riding on my bike. The audio navigation instructions still come through on my Bluetooth earpiece, and the instructions are accurate even if my phone is in my pocket. 

Now I get to ride without anything cluttering up my handlebars, and my phone lasts long enough for the journeys I make.