You've charged your EV's drive-train battery to 80% (since charging to 100% is frowned upon if you're not going to use it right away on a long drive).
But then, life happens. Suddenly, you don't get to drive your EV for an extended period. How do you stop your 12v battery from going flat? The answer:
Preconditioning / Pre-conditioner Timers
Preconditioning is the process of your EV 'warming' it's self up, by using the drive-train battery. It's effectively like "warming up the engine" on a conventional internal-combustion engine (ICE) car. The only difference for EVs? It's designed to get the EV ready for use -- especially warming (or cooling) the batteries, and running the climate control (air conditioning).
It also readies the battery systems, and this includes running the system that charges your 12volt battery, from the drive-train battery.
Yes, pre-conditioning charges your 12volt battery
You can either manually run battery pre-conditioning (usually from the vehicle's smartphone app, or touch-screen). Or you can set a preconditioning timer, to run on a regular interval.
Whether you set a timer every-day at knock-off time, or just on the days you don't use your EV, that's entirely up to you. But pre-conditioning timers are the little-known secret-sauce to keep your EV's 12volt battery in good health. It literally charges your 12v battery.
So set a pre-conditioning timer in your EV today!
Pictured: The Volvo App, showing the preconditioning manual 'start' button. Also visible: the Volvo App "Timers" tab, which allows you to schedule a vehicle such as the EX40, or XC40 electric, for pre-conditioning, to keep the 12v battery fully charged when not in use.