I recently purchased the all weather cable for my nest Cam Battery. I plugged it I and it powered on but but it appears the camera is still running off the battery as 24hrs later I had a notification saying battery very low and it powered off. I switched the power off at the plug then switched it back on again and the camera came back on. The camera seems to be charging via the all earth cable but I thought it would run continually via the cable. Any ideas on how to set the cable as the only power source.
I'm not sure what you mean by an "all earth cable".
We have had a Google Nest Camera (Battery) plugged in with the optional power cable for 15 months and it stays charged and "Live" at all times in winter and summer. Your optional power cable should plugged in securely, with the cable feeding towards the FRONT of the camera. If you select your camera in the Google Home app and go to Settings | Battery, it should say "Plugged in" with an infinity symbol.
This is how it SHOUD work:
"For wired installation setups with a Nest Cam (battery), the wires power the camera directly. At temperatures below freezing, the battery won’t charge, but as long as the wired power source is available, the camera can operate in temperatures down to -4°F (-20°C)."