Which AC Wall Adapter / Charger & USB Cable Should be Used for Garmin GPS Devices?
For the safety of your device(s) and yours, always use the ones from Garmin, such as "AC Adapter Cable Kit" (Part Number: 010-11478-02 [for US]).
You can also get it from Amazon for a little cheaper.
As for the cable...
The device does not know if you have a 1A, 2A or 5A power source behind it. The device will only go into full power if paired with a special plug. This signaling is accomplished using the 5th pin in the USB-B connector.
Unfortunately, the 5th pin on a common cable does not leave the connector so you can't really configure it. Garmin adapter has it configured within the molded plug.
See http://www.poi-factory.com/node/46164 for further discussion.