Going Long With Your Garmin Using An External Battery

For what they are, Garmin bike computers have excellent battery life (generally ~10hrs). This capacity is enough to easily navigate and record 100-150 mile rides. If you try to go much further (especially if recording *and* navigating a route) you may find your recording (and your proof) cut short.

Garmin devices will accept a charge while operating normally so the answer is to get an external USB battery pack and plug it in.

Almost any USB charger will do but how you affix it to your bike will depend on the type you get, and the model of your Garmin. For example: Garmin 705’s have the USB port on the BOTTOM of the device which may be difficult to access if you have a wide stem. You’ll also want to check the HEIGHT of your computer if you have a ‘500 or ‘800 to make sure that the SIDE facing USB ports clear your stem cap so the USB plug will not be obstructed.

From what I’ve read, charging your computer at rest stops will not give you much of a boost. If possible, it is best to continuously feed the Garmin power until your external battery dies, then unplug and continue on with the internal. Here are a few pictures showing a Duracell Instant USB Charger attached to a Garmin Edge 800.

External battery pack affixed using the 'ol Garmin ziptie trick. Note the height of the steerer top cap to make sure that the cable has a straight line to the plug.
Duracell battery pack is very slim and the included USB cable is the perfect length. For weight weenies: This battery pack adds 91 grams to the 98 grams of the Garmin 800.

2 Thoughts to “Going Long With Your Garmin Using An External Battery”

  1. Hey Lachy,

    The Edge 800 remains in fully-functionaly GPS mode while the Duracell battery is plugged in. I purchased this more for insurance than to go as long as you are planning–The Longest Day was 200 miles and it took my group 11hrs 37min which was right at the end of the Garmin’s 8-12 hour reported battery life. I ended up running the external battery for about 3 hours to make sure the recording didn’t get cut off and ended up having plenty of charge left in both batteries.

    The Garmin’s built-in battery is 1100 mAh and the Duracell is 1150 mAh so on paper your Garmin 800 should last about 16-24 hours with one external battery pack. Different weather and riding conditions contribute to that wide estimated range so you might actually want to have two external batteries on hand for your ride.

    I’d be interested to hear how it goes. The .fit format that the 800 and beyond use are theoretically fine for large recordings but I haven’t actually seen results from rides as long as you’re describing. Your device should have plenty of storage but there is a question of whether or not the device will get laggy as it continues to write to a larger and larger file. FWIW mine was able to navigate a route and record simultaneously for 208 miles with no problems.

  2. Lachy

    Hi there. Good write up. I am about to embark on a 20hour ride, and wondering in your experience, how many additional hours of battery life does the Duracell pack give you?

    I’ve also read that some USB charger packs will shut the GPS off and leave it in its normal ‘charging’ state. Is this the case with the edge800/Duracell pack?

    Thanks in advance

Leave a Comment