....you get what you pay for. I would get rid of the cheap cable and buy a genuine one to avoid damaging your iPhone.
Beware! I just bought a cheap, knock-off Lighning-USB cable on eBay for my iPhone 5. It behaves like a dimwitted cousin of the original Apple. The Lighning connection is not as readily reversible. It's erratic at best and easily confused. A bit "hit and miss". Although, once connection is established, it seems OK.