Here are a few reasons why this advice is given:

1. Battery Management: Lithium-ion batteries, which are used in most electric vehicles, have a longer lifespan if they are not constantly charged to the maximum or fully discharged. By limiting the battery charge to about 80%, the battery is less stressed, which benefits the overall lifespan.
   
   

2. Thermal Management: Charging to the maximum or discharging to the minimum can generate more heat in the battery. Heat can accelerate battery degradation and negatively affect performance. Limiting charging to 80% helps minimize heat buildup and promotes better thermal management of the battery.
   
   

3. Efficiency: Batteries generally perform most efficiently in the middle range of their charge. Charging up to 80% keeps the battery in an optimal efficiency range, which can result in better energy consumption and potentially a greater range.

It is important to note that charging to 80% is particularly relevant for daily use. If you are planning a long trip or need a greater range, you can, of course, charge the battery to a higher percentage. Modern electric vehicles often also have features that allow you to set the charge level, so you can choose how far you want to charge the battery.

It is always advisable to follow the specific recommendations of your electric vehicle's manufacturer regarding charging and maintaining the battery.