Here's the D-Link support reply:
"Date of Reply: 7/24/2014 7:42:08 AM
Products: DIR-510L
The device cannot be charged from a computer. It can only be charged from its power adapter.
Should you require further assistance with your D-Link products, please reply to this message, or call toll free at 877-453-5465.
Thank you for networking with D-Link"