The K is bigger in size, the location where the external power source is. I am not sure what the voltage is on the K series, i called Cuddeback support and they didnt have the voltage info for me. I dont install D batteries in my G cams. I made my own battery box last November with a solar panel. That was the last day i ever worried about battery life. I have said this before The G series Cuddeback is a great camera once you fix the battery life issue. I understand the cuddelink being active take power i found my own fix for it.