Careful children may notice that both the portable power supply and the laptop have the same 5000mAh battery, but the latter is much larger than the former.

So the question is: They are all lithium batteries, but why are the same batteries so far apart? It turns out that although they are both, but careful observation, the voltages V and Wh of the two batteries before mAh are different.

What is the difference between 　　mAh and Wh?

Milliampere hour (milliampere hour) is the unit of electricity, and Wh is the unit of energy.

These two concepts are different, the conversion formula is: Wh=mAh×V(voltage)&Pide;1000.

Specifically, milliampere-hours can be understood as the total number of electrons (the number of electrons passing through a current of 1000 milliampere-hours). But to calculate the total energy, we must calculate the energy of each electron.

Suppose we have 1000 milliamperes of electrons, and the voltage of each electron is 2 volts, so we have 4 watt-hours. If each electron is only 1v, we only have 1 watt-hour of energy.

Obviously, how much gasoline I like, such as one liter; Wh refers to how far one liter of gasoline can go. To calculate how far a liter of oil can go, we must first calculate the displacement. In this case, the displacement is V.

Therefore, the capacity of different types of equipment (due to voltage differences) is usually not measurable. Laptop batteries look bigger and more powerful, but they do more work than mobile batteries at the same time, and they don’t necessarily last longer than mobile power sources.

Why do agents use Wh instead of mAh as a limit?

People who frequently fly by plane may know that the Civil Aviation Administration has the following regulations on lithium batteries:

A portable electronic device with a lithium battery capacity not exceeding 100Wh is boarding, and it cannot be hidden in the luggage and mailed. The total battery power of all electronic equipment carried by passengers shall not exceed 100Wh. Lithium batteries exceeding 100Wh but not exceeding 160Wh require airline approval for mailing. Lithium batteries exceeding 160Wh shall not be carried or mailed.

We not only have to ask, why doesn’t the FAA use milliampere-hours as a unit of measurement?

Considering that the battery may explode, the intensity of explosive use is directly related to the size of the energy (Wh is the energy unit), so the energy unit must be specified as the limit. For example, a 1000mAh battery is very small, but if the battery voltage reaches 200V, then it has 200 watt-hours of energy.

Why do mobile phones use milliampere-hours instead of watt-hours to describe 18650 lithium batteries?

Mobile phone lithium battery cells are of great significance, because many people do not understand the concept of watt-hours. Another reason is that 90% of mobile phone lithium batteries are 3.7V polymer batteries. There is no combination of series and parallel between the batteries. Therefore, the power of direct expression Will not cause too many errors.

Another 10% used a 3.8 V polymer. Although there is a voltage difference, there is only a difference between 3.7 and 3.8. Therefore, it is okay to use mAh’s description of battery in mobile phone marketing.

What is the battery capacity of laptops, digital cameras, etc.?

The battery voltage is different, so they are clearly marked with watt-hours: low-end laptops have a power range of about 30-40 watt-hours, mid-range laptops have a power range of about 60 watt-hours, and high-end batteries have a power range of 80. -100 watt-hours. The power range of digital cameras is 6 to 15 watt-hours, and cell phones are usually 10 watt-hours.

In this way, you can use laptops (60 watt hours), mobile phones (10 watt hours) and digital cameras (30 watt hours) to fly close to the limit.