I’ve seen over the years a common product suggestion of adding a display, so you can see the % battery capacity remaining.I’ll explain why you won’t want it.The Lithium cells within a Powerbank are based on chemistry. The electrical energy is converted into chemical energy. In a typical Lithium cell this process of electrical to chemical back to electrical works reasonably well up to 300 cycles (varies by Lithium Ion, Poly, etc).As each cell has slightly different manufacturing outcomes, each cell has a unique cell capacity and ageing process.images%20(3)Hence any “% full” is a guess, either under or over estimating.The capacity is also affected by heat, so not only a function of how often you use them but where you use them.download%20(1)Finally how you use them also affects how much energy can be released. The DC-DC converter within an Anker Powerbank takes the progressively reducing voltage of the cell and steps it up to your desired Voltage.