As i recall my car read 12. 5 or 6 volts after being parked overnight with no parking guard.
Now as i run parking guard on 70mai Omni and / or Vantrue N5 my gauge read 11.8 volts the next day, as none of the two have the higher cut off values i would prefer.
Or that is it for sure do when the N5 system have been on parking guard, TBH i have not checked what volts are after overnight omni parking guard, but the camera are still on the next day cuz it pan around when i enter the car.
Having the N5 on overnight with motion detect, both cameras was " dead " the next day.
Using 12.2 volts for cut off, and timer ( 3 hours ) i have never really seen any dip in the voltage as the 3 hours are nothing.
I would not like to be in a place where i feel parking guard for as long as my battery will allow is needed, then i think i would prefer to move to a better place or park in a better place.
IF ! i was in such a place, i would add a charge / battery splitter like campers have, and then a AGM battery dedicated to dashcam use.
Or maybe a dedicated dashcam power pack with 1 - 2 additional packs to extend the time it can work.
But both of those scenarios are probably more than i would like to spend my meager pension on.
then you could have full recording for x hour
That would not work as running regular continuous recording are not advised as it generate the maximum heat inside the camera itself, that is why there are things like Low bitrate or time lapse for parking guard, A : to generate as little heat as possible and B: to have as little as possible parking guard files.
So running regular recording for X hours on a sunny day, well that will just increase the chance that your system shut down due to high heat, probably even before a very delayed parking guard set in.
AND ! only a few systems are able to automatic boot up once it have cooled down,,,, like very very few systems can do that. the norm is heat shut down = permanent shut down until you start your car again.
Okay i know in Denmark and the UK those blue skies and 25 - 30 deg C summer days are not frequent, hell this year we Danes havent even had just 1 day with 30 deg C.
This past July here the wettest one on record, even if we have not had any catastrophic ammounts of rain, then we still had 2 X the norm for the month.