c710-2856 charging

We first recommend your friend to remove and reinsert the battery in his Chromebook and then try charging it. To do this, you can follow the steps below:
1. Unplug the power adapter from your Chromebook.
2. Remove the battery from the bottom of the Chromebook. Push the slider on the bottom to the right to release the battery.
3. Re-insert the battery.
4. Plug the power adapter back into the Chromebook and a power outlet. See whether the battery is charging by checking the charge indicator light next to the power port.

(Important: I found the following Google support page mentioning a resolution for "Battery won't charge" issue on Cr-48. I am not sure if this link will benefit you but you can consider following steps 5 and 6 in the same.
https://support.google.com/chromebook/answer/183064?hl=en )
If the issue still persists, your friend can try charging the device by plugging in the power adapter to a power supply point different from the one he usually uses. This is just to check if there is any issue with the power supply.

If this does not resolve the issue, he may need to check if there is any issue with the power adapter. To do this, you can ask him to try using another power adapter (if possible) and see if that resolves the issue.

If the issue still persists, you may need to contact Acer support through the following link:
http://us.acer.com/ac/en/US/content/service-contact

Hope this will resolve your issue.