Like many other Garmin Edge 500 users, I was more than a bit annoyed to find that I couldn’t charge the unit while in use, or even charge it from an external battery when stopped without the ride resetting.

My cheap and cheerful solution, assuming you have an external battery already, is a USB On-The-Go cable, which works out a hell of a lot cheaper than any official solution.

I used a USB Mini Male to USB Female adaptor, with a USB Male-to-Male plugged into the female and my battery. Total cost, £3.57 (from Amazon, free shipping).

I’ve not tried rigging up the cable onto the mount yet, but I reckon a 90 degree USB Mini plug would fit underneath the mount – whatever you do the important part is the OTG cable which stops the unit going into ‘PC Mode’ when a battery is connected.

I can’t say for sure, but something like this would probably do similar.

http://www.portablepowersupplies.co.uk/portapow-fast-charge-usb-adaptor/

There are a number of places that do things like this, or in a cable form. Basically it just shorts out the data line so the device thinks it’s only connected to mains, and not a PC. Allows devices to draw more power also as on a PC they are often limited to 500mA.