Why is the power bank running out of power? It's not the fault of the false standard!

Do many friends feel that the mobile power in their hands will be dead after a few recharges? Why does it always feel that the capacity is so high that it is not enough? In fact, this is really not a problem of mobile power "virtual standard".

Speaking of the topic, nowadays mobile power is usually in the specifications of 5000mAh, 8000mAh or even 10000mAh, which sounds really big. Especially the mobile power bank in the last two years, looks more and more beautiful, and has more capacity than before, but it still looks the same-why can't it be charged a few times and then it runs out?

In fact, any mobile power supply has a conversion rate. The upper limit voltage of lithium batteries is 4.2V (usually 3.7V), and the charging voltage can only be charged from high voltage to low voltage. No matter what kind of lithium battery is used, the mobile power supply needs Cell phones and tablets can be charged only after the voltage is boosted to 5V. The process of boosting the lithium battery from 4.2V (3.7V) to 5V will consume 10%-20% of its capacity.

For example, the nominal capacity of the mobile power bank is 10000mAh, the battery cell voltage is 3.7V (generally lithium battery voltage is 3.7V), and the output voltage of the USB interface is 5V. Assuming no loss, the output capacity = (battery voltage×battery Capacity) × conversion rate÷ output voltage, which is (3.7V×10000mAh)×100%÷5V=7400mAh.

But there is still no loss. Assuming that the mobile power supply in your hand has a conversion rate of 92% (currently very high), then according to the output capacity = (battery voltage × battery capacity) × conversion rate ÷ output voltage, it is equivalent In (3.7V×10000mAh)×92%÷5V=6808mAh, that is to say, the actual output of the 10000mAh mobile power bank is less than 7000mAh at a conversion rate of 92%. Moreover, this has not considered the impact of peripheral circuits, cables, etc. (it will also consume a part of the power, which is less than the loss of conversion efficiency)! Do you understand this?

Therefore, don't think that 10000mAh is 10000mAh, and the ideal situation should be a 30% discount, not to mention those products with a conversion rate of about 8x% (the copycat power supply may be lower).