The battery life of my Edge 820 Explore has become so poor that I have to take a portable charger on every ride. Even a 50 mile ride will cause the battery to run out. I acknowledge that I use heart and cadence sensors, a varia radar, bluetooth and navigation, but these are functions that the unit is designed for, so the battery ought to be able to cope with them. Is anyone else having this issue? It is certainly much worse now than it used to be.