Well, google maps does basically all of this for free so...
Anyhow, the few times I wanted to make a custom route and have turn by turn prompts I just used google maps. Sure it has some deficiencies and glitches but it worked well enough and free, already installed, and I don't have to sign up for something or configure a profile, etc.

As far as battery life I haven't run into any concerns on trips of just a few hours using google along with endo (for tracking stats) with my screen cranked up full (but off most of the time) with cell and gps turned on. Additionally I have a whole extra battery, and then for multiday trips without possibility of charging I am shopping around now for one of the 18650 battery packs with usb plug.