Why does the lithium battery protection board need a pre-charge function?

With the continuous development and progress of science and technology, lithium batteries have the advantages of high energy density, small size and light weight. In the mobile phone and notebook computer market, it has basically completely replaced other batteries and has a 100% market share. At present, Lithium batteries are rapidly expanding into power tools, electric bicycles, and other applications, and their broad market prospects are increasingly recognized by the industry. As the core component of the lithium battery, the lithium battery protection board has attracted more and more attention. As the name implies, the lithium battery protection board is the protection of multiple lithium batteries, with the main protection functions of preventing overcharge, overcurrent, overdischarge, and short circuit. Today, the Chinese Chuangfa will learn with everyone why the lithium battery protection board needs a pre-charge function?

The operating voltage of the battery ranges from 2.5V (carbon negative battery: 3V) (power: 0%) to 4.2V (power: 100%). When the voltage is less than 2.5V, the discharge is terminated. At the same time, the internal protection circuit The current consumption is also reduced to the lowest (discharge circuit is closed). Of course, in actual applications, due to different internal materials and better battery protection, the discharge end voltage can be in the range of 2.5V~3.0V. When the voltage exceeds 4.2V, The charging circuit is terminated to protect the safety of the battery; and when the operating voltage of the single battery drops below 3.0V, we can consider the over-discharge state, and the discharge circuit is terminated to protect the battery. When the battery is not in use, the battery should be charged to 20% % Of the battery, and then store it in moisture-proof.

Because the lithium-ion battery has a high energy ratio, it is necessary to strictly avoid the phenomenon of overcharging and overdischarging in the use of the battery. Overdischarging will cause the active material to degrade It is difficult to recover. At this time, if you enter the fast charging mode (high current) directly, it will damage the battery, affect the service life and may cause invisible danger. First charge to 2.5V or 3.0V with a small current (C/10) , And then converted to fast charge is necessary. Although the current lithium-ion battery is equipped with a protective plate in the application, under normal circumstances, the probability of over-discharge will be very small, but without the pre-charge function, in the following situations It may still bring the hidden danger of over-discharge,

1. The protection board fails.

2. The self-discharge rate of long-term storage (5%~10%/month).

Therefore, the low-current precharge function can effectively solve the charging problem of over-discharged batteries.