Is it better to start out running the Garmin off it's internal battery, then plug in the external battery pack when Garmin internal battery gets low -OR- have it on the external battery pack from the start? Does it even matter? If you should switch when the internal battery gets low, how low?
I just plugged my external battery in from the start and launched the 520 ride. it worked fine. at the end of 132 miles the garmin still showed 100% battery. definitely takes the worry out of using the 520 for long rides
I use an external battery for brevets: a long'ish Anker 5,400mAh. It lasts for days, at least when the backlight is turned down to 10%. (The 520 seems to default to 100% with external power no matter the previous setting.) I wrap the battery in a zipbag and tape it to my stem with electrical tape. I leave the battery connected at all times to avoid having to fiddle with things. It's OK in light rain but downpours always have me worried.
