I once heard my friends said she bought a power bank which disappointed her. She tested it by charging her smartphone and found out that the capacity was not as high as 10,000mAh.
So, is the capacity of a 10,000mAh power bank as high as 10,000mAh?
Today, I would like you to know the consensus in the industry which is unknown to the general public and some knowledge about the power bank.
It is similar to the fact that you can only get a little over 50GB from 64GB memory cards; you can't get 128GB storage memory from 128GB smartphones.
It is a kind of consensus in the industry. Those who do not know it think that they are fooled. You won't complain as long as you know something about it.
The available power banks have two capacities:
1. Battery cell capacity.
2. Rated capacity.
The 10,000mAh and 20,000mAh in the advertisements are about the battery cell capacity.
What can be used is the rated capacity. There is no doubt that the rated capacity is lower than the battery cell capacity. The difference is enormous, far beyond 100mAh or 200mAh.
For example, the actual output capacity (rated capacity) of a Xiaomi 10,000mAh power bank is only 6,500mAh.
The difference is 3500mAh. Don't the manufacturers fool us?
Of course not. Many factors lead to the difference, among which the most important is the conversion rate.
As for most power banks, the voltage of each battery cell is 3.7V. When charging a smartphone, the battery voltage should be increased to 5V, so the conversion rate is only 3.7/5=74%. In addition to other kinds of power consumption, such as the wires and the battery cells, only around 6,000mAh can be used out of 10,000mAh.
If you can find the capacity on the product, you won't think that you're fooled.
However, the main problem is, due to considerable consumption, most manufacturers only advertise the battery cell capacity of 10,000mAh, without mentioning the rated capacity. (It's not the case with Xiaomi power bank. There is the rated capacity on the web page of the product.)
That's the reason why many people don't think the capacity of their power banks is as high as 10,000mAh, and it is the manufacturers to blame.
Of course, we can't rule out that quite a few unbranded power banks are falsely tagged. For instance, a 10000mAh one is tagged 20000mAh. It is recommended that you buy a power bank from famous brands to avoid being fooled.
Finally, I would like to talk about how to know whether you can take a power bank onto a plane or not.
Many airlines stipulate that the rated energy of a power bank should not exceed 100Wh. How to calculate and know whether the rated energy of your power bank exceeds the threshold?
At present, the "rated energy" of a small number of power banks is stated on the products. If it is not marked, use the simplest formula to calculate it:
Rated energy = (cell voltage x cell capacity) / 1000.
For example, by using the formula, we can find that the rated energy of a 3.7V 10000mAh power bank is 37Wh, which is lower than 100Wh.
Thus, it can be taken on the plane.
Isn't the method simple? Well, that's all. I hope that it will be useful to all of you.