Originally Posted by
Bald Paul
Garmin does offer an extended battery that will mount below a Garmin GPS unit on an out-front mount that works very well.
Nice but very expensive ($130).
Originally Posted by
Bald Paul
Anker makes auxiliary power supplies. I use one that is about the same diameter as my seat post, and attaches to it with 1/4 turn mounts. A USB cable can charge my Varia unit if the internal battery gets low.
These (at about $10) are likely going to be a better choice for more people.