Science popularization: the difference between mAh and Wh in the battery | love playing computer - 上海419贵族宝贝-上海后花园1314-上海品茶网-阿拉爱上海

One of the major factors restricting the development of smart phones is the battery of mobile phones. For many years, it can be said that the battery of mobile phones has been standing still. The performance of mobile phones has improved, but there is still no good solution for the battery's endurance. Because of this, the mobile power market is so hot. But for those who buy mobile power, they don't even know the unit of battery capacity. They even mistakenly believe that the cell phone battery of 6000mAh is better than the laptop battery of 5600mAh.

Once, my friend looked at the camera battery on my desktop and said, "Your camera battery is so much larger than my mobile power supply. How come its capacity is only a little larger. "As shown in the figure above, the mobile power supply on the left is 5200mAh, while the camera battery on the right is only 6600mAh.

In terms of volume, the lithium battery on the right is at least twice as large as the one on the left, but the 6600 is definitely not twice as large as the 5200. Is this battery empty? Absolutely not. Are there bricks in it? No guarantee.

In fact, if these two batteries are mobile phone batteries, their capacity can be compared with mAh. But if they are not the same type of products, it may be wrong to compare them directly. Aren't they all lithium batteries? Aren't they all the same? Why can't we compare? Although they are lithium batteries, careful friends will notice that the voltages of these two batteries are different, that is, because of the voltage, there is no comparability between the mAh numbers.

The Lenovo laptop battery shown in the figure below is only 5600mAh, which is less than three Xiaomi batteries.

Generally speaking, the physical meaning of battery capacity is how much charge the battery can hold or release. We usually use Ah (ampere hour) or mAh (milliampere hour) to express it.

According to the definition formula of current: I ＝ Q ／ t, we can see that Q ＝ It, the unit of current I is mA (milliampere), t represents time, and the unit is hour, so our battery capacity unit is mAh.

That is to say, if the capacity of a battery represents 1000mAh and the current is 100mA when it is working, it can theoretically supply power for 10 hours.

However, we can see from the formula that Q=It does not involve voltage, so this unit can only indicate how many coulombs of charge can be contained in the battery. However, it does not say how much work the battery can do or what the maximum power the battery can provide. Different types of products have different working voltages. Therefore, we often see a number in Wh next to mAh. The work that the battery can do W=UIt=UQ, the unit of voltage U * current I is W (watt), so W in the battery is expressed in Wh, which indicates how much work the battery can do.

Just now, the voltage of the 6600mAh battery is 14.4V, 14.4 * 6600=95.04Wh, and the work that can be done when it is released is 6.6 * 14.4 * 3600=342144 joules.

Generally, the mobile phone voltage is 3.7, so the work that can be done by the above 5200mAh mobile power supply theoretically is 3.7 * 5200=19.24WH, 3.7 * 5.2 * 3600=69264 joules.

Wh is a quantity in direct proportion to voltage, current and time. While mAh is usually used as an indicator of battery charging and discharging, which is proportional to the charging (discharging) current and time of the battery. To make it comparable or convertible with Wh, you must also know the battery voltage. In short, Wh=mAh/1000 * voltage.