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.
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.
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.
For any given desired output Wattage, if you want more performance the cell is unable to provide it for less capacity. So “want more, get less”.
So when a display indicates say a Powerbank is half full, that is a wild guess, as it depends on what device you connect and so the Wattage drain (higher Watts = less Watt-hours), the temperature you’re operating at (higher temps = lower capacity) and how old is the cell.
With clever electronics you can measure periodically cell ageing and look at how much energy was released at the last discharge, but only if you do a full discharge is that updated to be accurate, so for partial charge / discharge you cannot accurately measure the progressively lowering capacity.
So I have been very happy with Anker’s traditional “4 lights” as I know 3 lights is roughly 3/4th full and 2 lights is roughly 1/2 full, etc. I knew if I had a % display it’s going to be significantly off. A gimmick. I also knew if a half-full was going to be used on a larger device I’d get much less of that “half” than on a smaller device.
The more accurate you attempt to state capacity the more wrong you become.
I know to add display adds costs and weight, and I know it’s all contextual. Personally I don’t want a bulkier expensive gimmick display. Do you?
Next - why you don’t want high performance portable charger.
