The car can't possibly know if the owner is planning a 500 mile trip the next day. The only "safe" approach is to assume they are and top up all batteries every time it is plugged in.
If the owner plugs it in every day, how does this impact the usable life of this new battery?
* With lithium ion you don't want to sit at 100% all of the time, but it is fine to always keep it topped off to ~80% or so. Topping it off daily is good.
* If you are someone who doesn't want to worry about not going to 100% all of the time the new iron based batteries (featured in base model 3 right now for instance) don't care, you can let those sit at 100%, and they are safer too. The downside is less total range range and/or more weight.
GM in their Volt and Bolt holds back a percentage of the battery capacity so that at 100% of charge the battery pack is only charging to 85-90% and when it discharges to 0% the pack is actually not at zero. They do this to limit stress on the cells and to ensure longer service life for the battery pack.
The car can't possibly know if the owner is planning a 500 mile trip the next day. The only "safe" approach is to assume they are and top up all batteries every time it is plugged in.
If the owner plugs it in every day, how does this impact the usable life of this new battery?