Cadex Electronics CEO Isidor Buchmann tells the site that ideally users would charge their laptops to 80% and then drain them to 40%, prolonging their battery life by up to 4x.
The reason is that each cell in a lithium-polymer battery is charged to a voltage level. The higher the charge percentage, the higher the voltage level. The more voltage a cell has to store, the more stress it’s put under. That stress leads to fewer discharge cycles. For example, Battery University states that a battery charged to 100 percent will have only 300-500 discharge cycles, while a battery charged to 70 percent will get 1,200-2,000 discharge cycles.
This is simple in theory but much harder in practice. The report suggests timing how long it takes your device to charge from 40% to 80% and then setting a timer when you first plug your laptop in to charge.
If you can remember to follow Buchmann's advice, a four times increase in battery life is a significant improvement.