What are the common adverse reactions of lithium battery protection boards?

Analysis of common failures of lithium battery protection board 1. No flash, low output voltage, no load: This type of failure should first eliminate the bad battery (the battery originally has no voltage or the voltage is low). If the battery is bad, the protection board should be checked. Self-consumption, to see if the self-consumption of the protection board is too large and the cell voltage is low. Assuming that the cell voltage is normal, it is because the entire circuit of the protection board is blocked (components are soldered, false soldered, FUSE is poor, PCB internal circuit is blocked, vias are blocked, MOS, IC is damaged, etc.). The specific analysis process is as follows: (1) Connect the black test lead of a multimeter to the negative electrode of the battery cell, and connect the red test lead to the FUSE, R1 resistor terminals, the Vdd, Dout, and Cout terminals of the IC, and the P+ terminal (assuming the battery cell voltage is 3.8V). Analyze section by section, these check points should all be 3.8V. If not, there is a problem with this section of the circuit. 1. The voltage at both ends of the FUSE has been changed: check whether the FUSE is turned on, if the lead is normal, the internal circuit of the PCB board is not open; if the lead is not correct, there is a problem with the FUSE (bad incoming material, overcurrent damage (MOS or IC control failure), There is a problem with the material (the FUSE is burned out before the MOS or IC is activated), and then short-circuit the FUSE with a wire, and continue to analyze later. 2. The voltage at both ends of the R1 resistor has changed: check the resistance value of R1, if the resistance value is abnormal, maybe It is a virtual welding and the resistance itself is cracked. If the resistance value is not abnormal, there may be a problem with the internal resistance of the IC. 3. The voltage at the IC test terminal is changed: the Vdd terminal is connected to the R1 resistor. The Dout and Cout terminals are abnormal because the IC is virtual. Welding or damage. 4. If there is no change in the previous voltage, check that the voltage between B- and P+ is abnormal, it is because the positive through hole of the protection plate is blocked. (2) Connect the red meter pen of the multimeter to the positive electrode of the battery and activate the MOS tube, The black test lead is connected to MOS tube 2, 3, 6, 7 and P- terminal in turn. 1. If the voltage of MOS tube 2, 3, 6 and 7 has changed, it indicates that the MOS tube is abnormal. 2. If the MOS tube voltage is not The change, the P-terminal voltage is abnormal, it is because the negative through hole of the protection board is blocked. Two, no short circuit protection: 1. VM terminal resistance has a problem: a multimeter can be used to connect the IC2 pin, and the other to the MOS connected to the VM terminal resistance. The pin, confess its resistance value. Look at the resistance and IC, MOS pin for false welding. 2. IC, MOS malfunction: because the over-discharge protection and over-current, short-circuit protection share the same MOS tube, if the short-circuit malfunction is due to If there is a problem with MOS, this board should have no over-discharge protection function. Three, battery short-circuit protection without self-recovery: 1. The IC used in planning does not originally have self-recovery function, such as G2J, G2Z, etc. 2. The short-circuit recovery time of the instrument setting is too short , Or the load is not removed during the short-circuit test. For example, the test lead is not removed from the test end after the short-circuit test pen is short-circuited with the multimeter voltage file (the multimeter is equivalent to a load of several megabytes). 3. Leakage between P+ and P-, If there is impurity rosin between the pads, the impurity yellow glue or the capacitance between P+ and P- is broken down, and the breakdown is between ICVdd and Vss. (The resistance is only a few K to a few hundred K). 4. Assumption None of the above is a problem. Maybe the IC is broken down, you can check the resistance between the pins of the IC. Fourth, the internal resistance is large: 1. Because the internal resistance of MOS is relatively stable, the internal resistance is large, the first suspect should be The internal resistance of FUSE or PTC is relatively simple to change components. 2. Assuming that the resistance of FUSE or PTC is normal, check the via resistance between the P+ and P- pads and the component surface according to the protection board structure. Perhaps the via has a micro-break phenomenon and the resistance is relatively large. 3. Assuming that there is no problem with the above, it is necessary to doubt whether the MOS is abnormal: firstly, confess whether there is a problem with the welding; secondly, the thickness of the board (whether it is simply bent), because of the bending Sometimes it may cause the pin welding to be abnormal; then put the MOS tube under the microscope to observe whether it is broken; after all, use a multimeter to check the resistance of the MOS pin to see if it is broken down. Disclaimer: Some pictures and content of the articles published on this site are from the Internet. If there is any infringement, please contact to delete. Previous: How to solve the bottleneck caused by the battery to the new energy vehicle?