Common bad analysis of lithium battery protection board

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 correct. The self-consumption of the protection board is too large, resulting in 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 detailed decomposition process is as follows: (1) Connect the black test lead of a multimeter to the negative electrode of the battery, and connect the red test lead to the FUSE, R1 resistor ends, the Vdd, Dout, and Cout terminals of the IC, and the P+ terminal (assuming the battery voltage is 3.8V). Decompose it section by section, and 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 if the FUSE is on, if the lead is normal, the internal circuit of the PCB board is not open; if the lead is not, there is a problem with the FUSE (bad incoming material, over-current 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), then short the FUSE with a wire, and continue to decompose. 2. The voltage at both ends of the R1 resistor has changed: check the resistance value of R1, if the resistance value is abnormal, then It may be a virtual solder, 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 of the IC test terminal is changed: the Vdd terminal is connected to the R1 resistor. The Dout and Cout terminals are abnormal because of the IC 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 board is blocked. (2) Connect the red test 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 is changed, it indicates that the MOS tube is abnormal. 2. If the MOS tube voltage is changed If there is no change, the P-terminal voltage is abnormal, it is because the negative via of the protection board is blocked. 2. There is no short-circuit protection 1. The VM terminal resistance has a problem: you can use a multimeter to connect one test pen to IC2 pin, and one test pen to the MOS connected to the VM terminal resistor. 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, the board should not have 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 straightest way to confess whether the IC or MOS is malfunctioning is to question the suspected element. Replace the device. 3. Short-circuit protection has no self-recovery 1. The IC used in the 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 Use the multimeter voltage file to short-circuit the test leads without removing the test leads from the test end (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, ICVdd to Vss is broken down. (The resistance value is only a few K to a few hundred K). 4. Assuming that there is no problem with the above, perhaps the IC is broken down. 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 and large internal resistance occurs, the first suspect should be the relatively simple change of the internal resistance of FUSE or PTC. Components. 2. Assuming that the resistance of FUSE or PTC is normal, test the via resistance between the P+ and P- pads and the component surface according to the structure of the protection board, or The micro-breaking phenomenon may occur in the via hole, 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 (is it simple bending), because the bending may cause the pin welding to be abnormal; Put the MOS tube 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: Some pictures and content of articles published on this site are from the Internet. If there is any infringement, please contact to delete. Previous: Is it better to choose lithium batteries or lead-acid batteries for electric vehicles?