At least if the car is parked in the drive, or out on the street, and has central locking, there is a good chance it won't lock if a door has not been closed fully, so you do get a second opportunity to get it sorted and stop a potential flat battery situation. Motor vehicles these days can also have interior lights fitted in boots and front occupant foot-wells. Sometimes they don't have any on/off switches for when boots and doors are left open in daylight hours creating an unnecessary battery discharge.
So it's a good idea to switch off the ones that you don't use on a regular basis, especially the ones that operate automatically when doors, glove-boxes and boots are opened.
And what about the ignition key itself? If keys are left in the auxiliary position after the engine has been switched off, battery power will continue to feed to accessories left on, such as entertainment systems.
In addition, on the modern fleet, other behind the scenes on-board electronic communication systems can also remain partially active and continue to feed off the battery until the ignition is either turned off completely or in some cases the ignition key is physically removed from the ignition lock.
Left for too long, the end result will be a dead flat battery.
To avoid this situation, it's best to get into the habit of removing the keys from the ignition completely after engine shut down to ensure there are no unwanted and potential long battery drain periods.
But the ignition key is on the way out and being replaced by a proximity sensor which can remain in pockets, wallets and handbags and still provide a signal to start the vehicle with the simple push of an in-dash button.
But even this system can flatten a vehicle's battery if not shut down properly.
If a vehicle has an automatic transmission, then it must be placed into the "park" position before pushing the ignition on/off button to turn the engine off. Like the key system, failure to carry out the correct and full shut-down procedure can mean battery voltage will continue to be fed to numerous on-board electronic systems and over time flatten the battery.
The recommendation from one of the industry gurus I spoke to recently on this subject is to remove the proximity sensor from the vehicle completely and keep it well away from the vehicle to avoid a long-term slow battery drain. He has seen a flat battery result from the proximity sensor being left hanging on a hook in the garage right next to the car.
Because not every vehicle manufacturer has the exact same communication or ignition system, it's vital you get to know how your particular vehicle works in regards to potential battery drainage.
Don't rely on what others say as their shut-down procedure may work fine for them but not for your particular make/model of vehicle. Plus it may not be until you leave your vehicle unused for a couple of days that the flat battery problem surfaces.
And as some vehicles age, you can bet the house on the fact a lot of batteries will be automatically replaced for all the wrong reasons.
