gps - Battery drains even when plugged in while using Nav app on long road trips

I have a Nexus S running Android 4.0.3 and Google Maps 6.8.1.

When I use the Google Maps navigation app, the battery slowly drains, even when plugged into my car charger. After 5-6 hours, the phone will shut down due to loss of power.

I have already tried:

• Using only 2G mode


• Configured all of my (configurable) apps not to check for updates, fetch mail, etc, except when I tell it to.


• Reduced CPU speed, changed CPU governor, etc

I've had limited success reducing the CPU speed too much, as it makes the nav app unresponsive when I set it too low.

I have not tried dimming the screen much, as I can already barely see it when driving with sun glasses on.

Is this normal behavior, or is my phone faulty (or misconfigured)?

What else can I do?

• Perhaps there's a better way to charge my phone (different charger/USB cable?)


• Perhaps there's some way to automatically disable the screen except when within a certain distance of a turn? I.e. if the screen auto-blanked after 5 minutes, then would re-activate whenever there were spoken instructions, that would be fine with me.


• Perhaps there's another nav app that's more friendly on the battery?

EDIT Even in my car, I use an A/C charger with a DC/AC inverter, rather than one of the round cigarette-lighter style chargers.