When you're VFR, you can shut down components (or in many cases, your entire electrical system) to save on battery until you get to your destination. If you're in VMC, it's a little different story. And if you're in the clouds, you're probably not going to want to shut down a whole bunch of power-consuming components and fly partial panel to your landing destination. If you're in IMC, you need to get out of the clouds quickly, because you don't want to be relying on your battery as your only source of power. It all depends on your battery's condition, and how much your equipment is drawing from it. Maybe it's 15 minutes, and maybe it's an hour and 15 minutes. 9999999 of each craftable resource, and. Access to repeatable quests such as bozark horde, quarantine zones.
Levels-Survivor25 (max)-Agility24 (max)-Power24 (max) - All quests complete including bozark horde, some small quests from season pass may not be completed. Should be along the lines of 12.X volts with the car off, and 14+ with the car cranked. There should be a definite increase in voltage. Check the voltage with the car off across the battery terminals, then crank the car. But since there are so many factors involved, it's hard to tell exactly how much time you'll have. 100 Completed on Hard mode, requires 1.6.0+ I believe. If the battery light is on, more than likely theres a voltage drop. If you have a 20 amp-hour rated battery, it means you can (most likely) draw 20 amps with your equipment, and the battery will last for an hour.
So if you're flying on battery power alone, how long will your battery last? It depends on a lot of factors, including your battery's age, the temperature, and how many amps you're pulling from it.