Well, first of all, you need to calculate the powerdraw from the complete hardwirekit with camera(s),
Next, you need to figure out what size (Ah / Wh) your battery is.
Take into account the car's own powerusage. It's typically around 5-25mA in "standby".
When you'll know the runningtime of the setup.
If you got a small battery with low amount of Ah'rs you won't be getting long runningtime / recordingtime in parkingmode with car off.
For me, i get almost 18hrs of recordingtime before cutoff is reached @12.0V.
If winter is hard, the recordingtime is lower due to cold temperatures affecting the battery.
A 80Ah battery on my Audi A4 isn't standard. It's usually only around 45Ah when sold off the productionline.
So, do the math, get the numbers of the gear and you'll know how much power you'll need to do the requested time of recording when the car is turned off.