More information on my Quest Battery Life Analysis
as of 26 Oct 2004

I have been experimenting with my Quest unit to determine the situation with respect to my short battery life observations.  I have assumed all along that the battery life indicator was a reasonable indicator of battery time remaining.  At least in my unit,  this has not turned out to be so.
1) I charged the battery up to full.
2) At the end of 2 hours and about 25 minutes (just sitting there, no backlight on), I got the "low battery" warning. The battery charge indicator on the trip computer page showed about 20% left.
3) I kept running the unit (no backlight) and at the end of about 3.5 hours, the battery indicator showed "empty" but the unit was still working fine.
4) I ran it a total of 10 hours more on battery (no backlight) and the unit worked fine although from hours 3.5 through 13, the unit showed no battery remaining.

Then I ran another series of tests on the airplane back from Zurich today.
1) I charged the battery up to full.
2) I plugged in the Mighty Mouse II external amplified antenna to the external antenna port. All operation was with backlight OFF.)
3) I started the unit (and antenna) running at 5:30AM (Atlanta time) and at about 8AM Atlanta time, (2.5 hours) it was showing "battery empty".
4) It ran on (again no backlight) until 11AM when it finally ran out of battery power.


My conclusion is: My unit is broken in that the "battery low" and "battery life remaining" indications in my particular unit are way out of calibration! The display indicates "no battery" when in fact it has a LOT of battery left. One other person has reported this to me and two others say their unit's battery indicator works fine. Must be a resistor selection error in some units in the DAC that measures battery voltage. I now believe that Garmin's expectation of 20 hours (internal antenna and no backlight) and 6 hours (automatic backlight and normal driving on route and internal antenna only) is reasonable.