How to measure Lithium battery voltage with the nRF51 ADC
I suspect that the answer to your questions are more or less in my comments to Lucas questions later in this thread. If you are using 8-bit sampling then the resolution of the ADC is 256. The voltage on the ADC input when the Lithium battery if fully charged: 4.2 * (2.2M/(2.2M+10M))=0.76V which should output 0.76/1.2*255=161 which is in harmony with your findings.
I suspect that the answer to your questions are more or less in my comments to Lucas questions later in this thread. If you are using 8-bit sampling then the resolution of the ADC is 256. The voltage on the ADC input when the Lithium battery if fully charged: 4.2 * (2.2M/(2.2M+10M))=0.76V which should output 0.76/1.2*255=161 which is in harmony with your findings.