About the Battery Model 3 has one of the most sophisticated battery systems in the world. The most important way to preserve the Battery is to LEAVE YOUR VEHICLE PLUGGED IN when you are not using it. This is particularly important if you are not planning to drive Model 3 for several weeks. When plugged in, Model 3 wakes up when needed to automatically maintain a charge level that maximizes the lifetime of the Battery.
There are many other similar. Varying qualities and prices.
If you keep the car plugged in with it’s not normal charger as others mentioned that good. Some people use trickle chargers on the 12v battery. But it’s largely a carryover from ICE cars.
There’s been back and forth discussion of trickle charging the 12V battery separate due to stresses of storage for months. Some say just use the app to force awake the car plugged into the charger while gone. Others state you need to put pop the hood and connect a trickle charger to the 12V. You might want to search the forum or start a separate thread. Or just check Google.