Common bad decomposition of battery protection board

1. No display, low output voltage, and no load: This type of defect should first 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 detected to see if it is correct It is because the self-consumption of the protection board is too large, which leads to the low battery voltage. If 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 steps are 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 detection points should all be 3.8V. If not, there is a problem with this section of the circuit. 1. There is a change in the voltage at both ends of the FUSE: detect whether the FUSE is turned on, if it is turned on, the internal circuit of the PCB board is not turned on; if it is not turned on, there is a problem with the FUSE (poor 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), then short-circuit the FUSE with a wire, and continue to decompose. 2. The voltage at both ends of the R1 resistor changes: detect the resistance value of R1, if the resistance value is abnormal, then It may be a solder joint and the resistance itself is broken. If the resistance value is not abnormal, there may be a problem with the internal resistance of the IC. 3. There is a change in the voltage of the IC detection terminal: the Vdd terminal is connected to the R1 resistor. The Dout and Cout terminals are abnormal, which is due to the IC Welding or damage. 4. If there is no change in the previous voltage and the abnormal voltage between B- and P+ is detected, it is because the positive through hole of the protection plate 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 the MOS tube 2, 3, 6, 7 and P- terminal in turn. 1. If the voltage of the MOS tube 2, 3, 6 and 7 has changed, it means that the MOS tube is abnormal. 2. If the MOS tube voltage If there is no 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 test pen is connected to the VM terminal resistance. MOS pin, confirm its resistance value. Look at whether the resistor and IC, MOS pin are soldered. 2. IC, MOS abnormal: due to the over-discharge protection and over-current, short-circuit protection sharing a MOS tube, if the short-circuit abnormality is Due to MOS problems, this board should have no over-discharge protection function. 3. The above are defects under normal conditions, and short-circuit abnormalities caused by poor IC and MOS configurations may also occur. For example, the BK-901 that appeared in the previous period, its model is' The delay time in the 312D' IC is too long, causing the MOS or other components to be damaged before the IC takes the corresponding action control. Note: The easiest and straightest way to determine whether the IC or MOS is abnormal is to check the suspected element. Replace the device. 3. Short-circuit protection has no self-recovery: 1. The IC used in the design 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 short-circuit detection. If you use the multimeter voltage file to short-circuit the test leads without removing the test leads from the detection 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. If there is no problem with the above, the IC may be broken down. It can detect the resistance between the pins of the IC. Fourth, the internal resistance is large: 1. Since the internal resistance of MOS is relatively stable and large internal resistance occurs, the first thing to suspect should be that the internal resistance of FUSE or PTC is relatively easy to occur. Changing components. 2. If the resistance of FUSE or PTC is normal, test the via resistance between the P+, u200bu200bP- pads and the component surface according to the structure of the protection board. Value, there may be micro-breaks in the vias, and the resistance value is relatively large. 3. If there are no problems with the above, it is necessary to suspect whether the MOS is abnormal: first determine whether there is a problem with the welding; secondly, the thickness of the kanban (is it easy to bend), because the bending may cause abnormal soldering of the pins; then Put the MOS tube under a microscope to observe if it is broken; finally, use a multimeter to detect the resistance of the MOS pin to see if it is broken. V. ID abnormality: 1. The ID resistance itself is abnormal due to virtual welding, fracture or because the resistance material is not good: you can re-weld the two ends of the resistance. If the ID is normal after re-welding, the resistance is virtual welding. If it is broken, the resistance will be in Cracked from it after re-welding. 2. ID via does not conduct: use a multimeter to detect 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: What are the advantages of lithium batteries for electric vehicles compared to lead-acid batteries?