An Investigation of GPS Battery Usage
Prepared 2017-01-14 by Bill Claff

Introduction

Geo-tagging of photographs is useful to some photographers.
I have used external GPS units to geo-tag my photos for many years.
I typically turn my GPS on when I leave my house and leave it on until I return.
Although I have never experienced any battery drain issues, battery drain is a common concern for GPS users.
To confirm my experience I conducted a controlled test.

The Test

I used a Nikon D7200 with a nearly fully charged battery and a Dawn Technologies Eco ProSumer M GPS unit.
I turned the GPS on and noted the battery charge level at intervals.
The camera was off between battery charge level checks.

Results

I let the battery run down to 3% before concluding the test. This is about as low as you can go.

Here is a graph of the results:

The error bars indicated the 0.5% accuracy of the battery level. The linear fits to the data seem quite good.

Conclusion

The GPS unit uses about 20.5 mAh and with a 1900 mAh battery takes over 84 hours (3 days) to run down.

It's clear that leaving the GPS unit on continuously has no material impact on battery life.