Laptop won't charge & I keep getting four constant beeps

My friend has a Dell Inspiron 15 N5010 laptop/notebook which has recently not been working so well and has a number of issues.

1. When the laptop is tued on it beeps four times in a row over and over - this continues even when once loaded into Windows (although the beeping volume drops)
2. When the charger is plugged in - it will never charge the battery e.g it stays at 0% regardless.
3. The time for some reason always changed to a random date/time in the past and I have to change this manually each time the laptop is rebooted.

I am presuming that this needs a replacement main battery & a CMOS battery (sometimes call coin cell battery)

Would this be sufficient to fix these problems? Does anyone know what the four beeps are for?