So the other day i left my charger at my friends place and since then i have bought a cheap 10$ charging cord from walmart. I used it to charge my phone (iphone 5s) and every time i plug it in it says something about it not being certified and it may not work reliably. Sometimes it charges it sometimes it doesn't. Anyways I used it to charge my phone for 20 minutes before I went to work. When I got to work it was at 60%. About an hour into my shift i went to check my phone and it was extremely hot and wouldnt turn on. I panicked. I plugged it in using a certified iphone cable from my work and it immediately turned on and showed 6% battery life. Anyways, is there anyway that it damaged my iphones battery? Should i stop using this cord. As well i'm charging it right now and it seems to be charging extremely quickly. Its not plugged into the wall just into my macbook.