Selection of battery capacity and battery charger
Theoretically, the smaller the charging current, the better the battery performance. If the charging time is too long, it must be unfriendly to users. Therefore, the general standard for charging is 0.1-0.2c. Here, C is the rated capacity of the battery. Taking a battery with a capacity of 10000 MAH as an example, the charging current is 2000mA. Theoretically, it can be fully charged within five hours, with capacity MAH = current MAH * time H. But in fact, in order to protect the battery, battery charging is also divided into three stages: constant current charging, constant voltage charging and wire current charging. Therefore, the actual charging time is greater than 5 hours or slightly greater than 6 hours. Calculation method of battery charging time: divide the battery capacity by the charging current and multiply by the coefficient 1.2-1.1. The unit of time is hour
Maybe you don't understand why you use constant current charging, constant voltage charging and wire current charging to charge the battery. Isn't this a waste of time? Let's introduce these three charging stages, and you will understand the mystery
Constant current charging is a charging stage in which the charging current remains unchanged and the charging voltage increases approximately linearly. If the battery is directly charged with a current of 0.1-0.2c, even if there are no other accidents, the battery life will be shortened due to excessive charging and heating. Therefore, at the beginning of constant current charging, the charging current remains unchanged and the charging voltage increases approximately linearly, so as to prolong and protect the service life of the battery
Constant voltage charging has different charging voltages according to different voltage levels. Therefore, you cannot select the charger only based on the current. For example, a battery charger charges a 5V battery, not a 12V or 6V battery.
According to different batteries, the wire current charging is also different. It is generally called floating charge current. Its size is closely related to the battery capacity. For example, the normal charging current < constant current charging current > of a 10000 MAH battery may not be as large as the floating charging current of a high-capacity battery. Excessive constant current charging current is most likely to cause overcharge of the battery, affect the service life of the battery, and even damage the battery. Because the most basic protection of the battery is two: don't overcharge and don't consume too much power. If these two rules are violated, the battery may be damaged immediately and the capacity may be reduced
But generally speaking, lithium batteries, for example, are equipped with charge discharge protection circuits. After understanding this, you may understand why battery charging requires three stages: constant current charging, constant voltage charging and constant current charging
The charging time of digital electronic product battery is generally designed to be 6 hours. The purpose of this is to ensure that users can fully charge the battery when they sleep, especially for digital products such as mobile phones and tablets, which are basically frequently charged. Therefore, users can insert electronic products before going to bed at night and fully charge the battery before waking up in the morning. This is also a more humanized consideration. Therefore, considering the longest service life of the battery and the convenience of users, the designer will minimize the charging current of the battery charger.