Lithium batteries are happiest between 20 and 80% state of charge. You should not store them outside of that range. Charging a little often also doesn't hurt your battery like many seem to believe.
Charging while cold is bad, but storing in cold is good.
Also, NiMh and NiCd batteries are different tha Lithium based ones. Check what type of battery you have. Phones and EVs are almost always lithium though.
To be clear, a car that uses either gasoline or diesel will have a lead acid battery and not a lithium battery. Electric cars have lithium. Just to clear up any confusion.
Quite a lot of electric cars will still have a lead acid battery for the low charge things like wipers, electric windows and electric mirrors. It's simpler to do that than to have a complicated system to step down the voltage to something they can accept from a lithium ion battery.
So essentially electric cars have two independent electrical systems that have nothing to do with each other. Interestingly this means that you can use an electric car to jump start an ICE car, even though a lot of people claim you cannot.
That said some electric cars do go the route of a step down transformer so check your car.
85% but yeah. You can also set them to slow charge. So my phone, when set to Night routine, will change these settings to 85% slow charge while I sleep. I've yet to need to top-up that charge but if I did, I just leave it plugged in while I get ready for the day (with night mode off)