Views: 4 Author: Site Editor Publish Time: 2024-04-18 Origin: Site
Function and selection method of protection board for lithium iron phosphate battery pack. Nowadays, lithium iron phosphate batteries are commonly used in amplifiers, LED flashlights, and small electromechanical devices. In order to enhance the safety of lithium battery packs, protective boards are necessary equipment. The lithium battery pack protection board is composed of electronic components and PCBs, and is always ready to monitor the voltage of the battery cells and the current of the charging and discharging circuit in a certain temperature and humidity environment. What are the common functions of lithium iron phosphate battery protection boards and how to choose them? These questions should be of great concern to everyone. Today, we will talk about them. For those who want to learn more about the functions of this lithium iron phosphate battery protection board, please read it carefully.
The reason why lithium iron phosphate batteries (rechargeable) need protection is determined by their own characteristics. Due to the material of the lithium battery itself, it cannot be overcharged, overdischarged, overcurrent, short circuited, or subjected to ultra-high temperature charging and discharging. Therefore, lithium iron phosphate battery components always come with a delicate protective plate and a current protector. The protection function of lithium batteries is usually completed by the cooperation of protection circuit boards and current devices such as PTC. The protection board is composed of electronic circuits, which accurately monitor the voltage of the battery cells and the current of the charging and discharging circuit in an environment of -40 ℃ to+85 ℃, and timely control the on/off of the current circuit; PTC prevents severe damage to batteries in high-temperature environments.
Ordinary lifepo4 battery protection boards usually include control ICs, MOS switches, resistors, capacitors, and auxiliary devices FUSE, PTC, NTC, ID, memory, etc. Among them, the control IC controls the MOS switch to conduct under normal conditions, making the battery cell conductive to the external circuit. When the voltage or circuit current of the battery cell exceeds the specified value, it immediately controls the MOS switch to turn off, protecting the safety of the battery cell.
When the voltage of the battery cell is between 2.5V and 4.3V, the first and third pins of DW01 both output a high level (equal to the supply voltage), and the voltage of the second pin is 0V. At this time, the voltage of the first and third pins of DW01 will be applied to the fifth and fourth pins of 8205A, respectively. The two electronic switches inside 8205A are in a conductive state because their G pole is connected to the voltage from DW01, that is, both electronic switches are in an open state. At this point, the negative pole of the battery cell is directly connected to the P-terminal of the protection plate, and the protection plate has a voltage output.
Overcharge voltage protection: To prevent battery failure caused by charging voltage exceeding the upper limit of battery usage voltage, leading to safety accidents
Overdischarge voltage protection: prevent deep discharge of lithium iron phosphate battery packs, avoid shortening battery life or causing safety accidents
Overcurrent protection: limit the current passing through the protection board and battery
Short circuit protection: To avoid safety accidents caused by battery short circuits
Temperature control switch: protects the battery pack and protection board from safety hazards caused by high temperatures
In order to protect the lifespan of the lithium battery pack, it is recommended that the charging voltage of the battery should not exceed 3.6V at any time, that is, the protection voltage of the lithium battery protection board should not exceed 3.6V, the balanced voltage is recommended to be 3.4V-3.5V, and the discharge protection voltage of the battery is generally above 2.5V.
The recommended maximum voltage for the charger is 3.5 strings. The larger the self discharge, the longer it takes to balance. Cells with excessive self discharge are already difficult to balance and need to be removed. So when choosing a lithium battery protection board, try to choose one with 3.6V overvoltage protection and one with a starting balance of around 3.5V.
When choosing a lithium battery pack protection board, the first step is to calculate the continuous discharge current provided by the battery based on the actual power of your own motor. For the assembly of batteries, it is important to pay attention to whether the self discharge of the batteries is balanced when connecting them in series. In short, when selecting a lithium battery pack protection board, the smaller the internal resistance, the better. The lithium battery pack needs to control the highest temperature during use, and it is best to keep the battery at the platform voltage when not in use.
In short, the lower the internal resistance of the protection plate of the lithium iron phosphate battery pack, the better, and the lower it is, the less it will generate heat. The current limiting size of the protective board is determined by the sampling resistance of the copper wire, but the continuous current capacity is determined by the MOS. When selecting, the smaller the internal resistance of the protective board, the better. The lithium battery pack needs to control the highest temperature during use, and it is best to keep the battery at the platform voltage when not in use.
