Why do lithium-ion batteries need to protect the board and lead-acid batteries not to protect the board?

Lithium-ion batteries have high energy density and strong chemical activity inside the battery. When the battery is overcharged, overdischarged and other abnormal use, the battery is very likely to be damaged, and in extreme cases, it can also cause fire and explosion. Therefore, a lithium-ion battery must have a monitoring system to monitor the voltage, current and other parameters of the lithium-ion battery at any time. Once it exceeds the preset threshold, the battery main circuit is directly shut down. By convention, to know and be familiar with the protection board, we first classify the protection board. 1. According to whether the program can be written, it is divided into hardware board and software version; 2. According to whether the charging and discharging are the same output port or two different output ports, it is divided into the same port protection board and the split port protection board. In actual use, the most common classification method is based on the number of lithium-ion battery strings that the protection board is adapted to, the type of battery cell, and the size of continuous discharge. Hardware board and software board The so-called hardware board means that there is no chip that can be programmed on the protection board, but it is connected according to a specific circuit, and the parameters of the protection board are fixed. This type of protection board is generally low in cost, simple in function, and difficult to achieve special logic control requirements. The software board is based on the hardware board with a programmable chip, so in addition to basic functions, this type of protection board can also achieve many special functions, as long as the program is modified and peripherals are added, such as remote detonation of the vehicle Lithium-ion battery in. In order to realize the function of protecting the battery, the protection board of the split port and the same port must be able to actively cut off the main circuit of the battery. Therefore, inside the battery pack, the main circuit of the battery must pass through the protection board. In order to control both charging and discharging, the protection board must have two switches to control the charging and discharging circuits respectively. In the same port protection board, these two switches are connected in series on a line, connected to the outside of the battery pack, and both charging and discharging pass through this line. In the port protection board, the battery is separated into two wires, which are connected to the charging switch and the discharging switch respectively, and then connected to the outside of the battery. The reason why the same port and split port protection boards appear is to reduce costs: the charging current of lithium-ion battery packs in general electric vehicles is smaller than the discharging current. If two switches are connected to one line in series, then the two switches must be in accordance with Big buy. In the case of split ports, the charging current is small, and a smaller switch can be used. The switch mentioned here is actually a MOSFET, which is an important cost of a lithium-ion battery protection board. It is easier to understand the number of strings according to the number of strings and the size of the continuous discharge current. The common 7 strings (three yuan 24v), 13 strings (three yuan 48v), 17 strings (three yuan 60v), and 20 strings (three yuan 72v). The protection board needs to collect the voltage of each string of cells, so the number of strings is different, the protection board is different. The current size determines the size of the switch (the number of MOS) as mentioned above, which has a great impact on the price. Disclaimer: Some pictures and content of articles published on this site are from the Internet. If there is any infringement, please contact to delete.