There's no hard rule, but most manufacturers and experienced owners converge on a similar range: keep daily driving between roughly 20% and 80%, and treat 0% as an emergency threshold, not a target.
Why 20-80% is the common guideline
Charging speed slows significantly above 80%, and repeatedly draining a lithium-ion battery close to empty adds more long-term stress than staying in a comfortable middle range — so the 20-80% habit balances convenience and battery longevity.
When it's fine to go lower
On a road trip, charging to closer to 90-100% before a long unavoidable stretch, or running down toward 10% right before a planned fast-charging stop, is a normal and reasonable exception to the daily habit.
What actually matters most
Consistently running a battery to 0% and immediately back to 100% repeatedly is the pattern worth avoiding — occasional full charges or low charges for a specific trip aren't a problem.
Is it bad to leave an EV plugged in at 100% overnight regularly?
Many EVs let you cap charging at a lower percentage (like 80-90%) for daily use specifically to avoid sitting at 100% for extended periods — check your car's settings if this is a regular habit.