It is the nav app keeping the display lit up like a Times Square billboard that is sucking the majority of your battery life down, by the way. Your suggestion stands, however.
You can lock the display and the voice directions still subsist. The battery drain is from the constant polling of GPS information in my experience though.
> The battery drain is from the constant polling of GPS information in my experience though.
Why would that use a lot of power though? It's just receiving a signal. I have the impression that it's when sending out a signal that a lot of power is used. And in that sense electromagnetic radiation at GSM, Wifi or visible spectrum-frequencies are all the same.
I'd say it's both keeping the screen on and constantly downloading new map information from the cellular network.
