Archos 80 G9 Charging

[staggering]

I had my sons tablet repaired with the usual loose usb connection and its still in place and not loose. However a month later I now have charging problem.
The green power light lights up and it said 'charging' but it doesn't. It used to charge and then when fully charged, the green light used to flash as its supposed to.
The battery has reached the stage now where it is so flat, it wont keep the tablet powered on so therefore it wont charge.

Is I the battery not accepting a charge or something else?

If it is, is there a good YouTube or video that shows one being taken apart etc as this tablet is out of warranty so I don't mind having a go

Any help really appreciated
Andrew