Portable Emergency AA Battery Charger Extender suitable for the Garmin EDGE 500

This comes highly recommended by other randonneurs.

I wonder if it works with the Edge 810?


Andrew Mead says:

 I start with the Gomadic plugged in so the Edge draws external power first and doesn’t put the AAs into a high current draw-down needed to recharge the Edge.

The Edge will alert me when it switches to the internal battery so I know when I’m down to my last 15 hours of power.  I suppose I could swap in new AAs at that point and continue indefinitely.