At the ABQ MM BFL we had a couple people who weren't able to complete the route due to batteries dying on their GPS making it difficult to navigate.  

There's a couple ways to address this, depending on the GPS, but in my case for events where I know I'm going to be testing the limits of my GPS battery life I attach a cheap supplemental USB battery (like this one from Amazon, a whole $8  http://a.co/2eqjIJj ) to the handlebar with some rubber bands and connect to my GPS with a short right angle mini-usb cable (like these, another $8 for TWO,  http://a.co/c6zMoni ).  With my old Garmin 705 and my 810 I can plug this in and it will extend the GPS life while the gps is running.  

As I understand it the Garmin 500 will not charge while on/running, so you need to test your GPS unit to make sure it can charge while powered on and running.  So, for an entire $16 you've extended your GPS battery life to probably 24 hours or more.

Next, I've recently started playing with an app available on IOS and Android called Gaia GPS.  For highly acceptable functionality a year subscription will set you back all of $20.  With this you can make any GPS enabled apple/android device a very good navigation tool.  You just need to plan ahead and make sure you've downloaded the base maps and tracks for offline use as you very likely won't have cell phone data when you need it.  I'll be populating Gaia with the NMES course as we go, I've already got the SYDC routes posted.  From here you can either save tracks to your own Gaia account, or download the GPX for use in any GPS device:

This can be a good option for an inexpensive back-up for your primary navigation GPS.  

In other news there's been some recent additions in the world of GPS bike computers from Wahoo and Lezyne that are quite a bit less expensive than Garmin.  I just don't have experience with them in the real world for back country nav so you'll have to do your own research on those.  Or if you have personal experience, give me a shout, I'd like to know about it.

Cheers,

Nate

--