OK, the battery is floating and has no reference to AGND!!!
Also the other problem may be that you need to bypass the buffer for AIN4 - the negative input or to bias this pin up to AGND + 100mV. Please have a look into the data sheet spec for the analog inputs.
Also I'm wondering why you not using directly the UART interface via the USB-Debug-adapter!?
Have you disconnected the appropriate jumpers on the adapter? Doesn't look like!
You can blow the adapter as well as the ADuC!