I would be careful about that. Some of the newer cars with electronic ignition circuitry will not start that way if the battery voltage drops low enough. Has to do with the vehicle computers and their minimum voltage requirement.
I would not be concerned about that part at all. battery voltage can drop to 10 volts and less when cranking at times and ignition and computer has no problems with that. A few years ago my daughter lost her alternator in here car coming back from college for weekend in her Saturn. It was late, dark and very cold too. I meet her and jumpered her off and charger it up 20 minute and then drove it for a while and did it again until we got it home 40 miles later. I had a Data chip in OBD2 port that records engine data and battery voltage and it showed than one time voltage dropped to 9 volts and engine still ran fine.