Won't charge long enough

Hi,

I have a 2DS and plugged it up to charge last night. I saw the light on, so I assumed it worked. I noticed later that it stopped charging. I plugged it up again, the light comes on for about 30 seconds, then the light turns off. The light turns back on if I unplug and plug the charger back in. I haven't dropped the 2DS and the cord is in good condition. Can someone help please?