Lithium battery protection board failure judgment

1. No flicker, low output voltage, no load, etc. The first step is to eliminate the bad battery (the battery originally has no voltage or the voltage is low). If the battery is bad, the self-consumption of the protection board should be checked to see if it is protection Excessive self-consumption of the board leads to low battery cell voltage. 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 pole of the battery cell, and connect the red test lead to the FUSE and 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. 2. There is no short-circuit protection 1. The VM terminal resistance has a problem: a multimeter can be used to connect the IC2 pin and the other to the MOS tube connected to the VM terminal resistance. Pin, confess its resistance value. Look at the resistance and IC, MOS pin for false welding. 2, IC, MOS abnormal: because the over-discharge protection and over-current, short-circuit protection share a MOS tube, if the short-circuit failure is due to MOS If there is a problem, the board should have no over-discharge protection function. 3. The above is a fault under normal conditions, or there may be a short circuit caused by poor IC and MOS equipment. For example, the BK-901 that appeared in the previous period, its model is '312D' The delay time in the IC is too long, causing the MOS or other components to be damaged before the IC makes the corresponding action and control. Note: The easiest and most direct way to confirm whether the IC or MOS is malfunctioning is to perform the suspected component Replacement. Three. Short-circuit protection without self-recovery 1. The IC used in planning has no self-recovery function, such as G2J, G2Z, etc. 2. The short-circuit recovery time of the instrument is too short, or the load is not removed during the short-circuit test, such as a multimeter. The voltage file is short-circuited and the test leads are not removed from the test end after the test leads are short-circuited (a multimeter is equivalent to a load of several megabytes). 3. Leakage between P+ and P-, such as impurity rosin or impurities between the pads The yellow glue or the capacitance between P+ and P- is broken down, and the IC is broken down between Vdd and Vss. (The resistance is only a few K to a few hundred K). 4. Assuming that there is no problem with the above, maybe the IC is broken, you can check the IC The resistance between each pin. Fourth, the internal resistance is large 1. Because the MOS internal resistance is relatively stable, the internal resistance is large, and the first suspect should be FUSE or PTC, which is relatively simple to change the internal resistance. 2. Assuming that the resistance value of FUSE or PTC is normal, the resistance value of the via hole between the P+ and P- pads and the component surface may be checked depending on the structure of the protection board. The hole appears micro-break phenomenon, and the resistance value is relatively large. 3. Assuming that there are no problems 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 the bending may cause the pin welding to be abnormal; then the MOS tube Put it under a 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. 5. ID abnormality 1. The ID resistance itself is abnormal due to virtual welding, cracking, or because the resistance material is not off: the two ends of the resistance can be welded from the beginning. If the ID is normal after rewelding, the resistance will be welded. If it is cracked, the resistance will be heavy. Cracked from it after welding. 2. ID via is not conductive: use a multimeter to check both ends of the via. 3. The internal circuit has problems: you can scrape the solder mask to see if the internal circuit is disconnected or short-circuited. Disclaimer: The articles published on this website are all from the Internet. If there is any infringement, please contact to delete it. Disclaimer: Some pictures and content of articles published on this site are from the Internet. If there is any infringement, please contact to delete.