“Lithium batteries are one of the types of batteries commonly used in life, and we are naturally very familiar with lithium batteries. In order to improve everyone’s understanding of lithium batteries, this article will introduce the lithium battery protection board, the main content is to explain the fault judgment of the lithium battery protection board.
Lithium batteries are one of the types of batteries commonly used in life, and we are naturally very familiar with lithium batteries. In order to improve everyone’s understanding of lithium batteries, this article will introduce the lithium battery protection board, the main content is to explain the fault judgment of the lithium battery protection board.
A summary of the abnormal causes of lithium batteries, including lithium battery capacity, lithium battery internal resistance, lithium battery voltage, ultra-thick size, open circuit, etc., the battery capital has briefly summarized and shared with you.
1. Low battery capacity
Causes: a. The amount of attached material is too small; b. The amount of attached material on both sides of the pole piece is quite different; c. The pole piece is broken; d. The electrolyte is less; e. The conductivity of the electrolyte is low; f. Not well prepared; g. The porosity of the diaphragm is small; h. The adhesive is aging → the attachment material falls off; i. The core is too thick (not dried or the electrolyte is not penetrated) j. The material has a small specific capacity.
2. High internal resistance of battery
Causes: a. Welding of negative electrode and tab; b. Welding of positive electrode and tab; c. Welding of positive electrode and cap; d. Welding of negative electrode and shell; e. Large contact resistance between rivet and pressure plate ;f. No conductive agent is added to the positive electrode; g. There is no lithium salt in the electrolyte; h. The battery has been short-circuited; i. The porosity of the separator paper is small.
3. Low battery voltage
a. Side reactions (decomposition of electrolyte; impurities in the positive electrode; water); b. Not well formed (SEI film is not formed safely); c. Customer’s circuit board leakage (referring to the battery cells returned by the customer after processing); d. . The customer did not spot welding as required (cells processed by the customer); e. burrs; f. micro-short circuit; g. negative electrode produces dendrites.
Four, super thick
a. Welding leak; b. Electrolyte decomposition; c. Undrying moisture; d. Poor cap sealing; e. Shell wall too thick; f. Shell too thick; g. Core too thick (too much material attached) ; pole pieces not compacted; diaphragm too thick).
5. Abnormal battery formation
a. Not well formed (SEI film is incomplete and dense); b. Baking temperature is too high → binder aging → stripping; c. The specific capacity of the negative electrode is low; d. . The cap leaks and the weld leaks; f. The electrolyte is decomposed and the conductivity is reduced.
6. Battery explosion
a. The sub-container is faulty (causing overcharge); b. The diaphragm closing effect is poor; c. Internal short circuit.
Seven, battery short circuit
a. Material dust; b. Broken when packing; c. Scraping (diaphragm paper is too small or not properly padded); d. Uneven winding; e. Not well wrapped; f. Diaphragm has holes; g. Burrs
Eight, battery disconnection
a) The tabs and rivets are not welded well, or the effective welding spot area is small; b) The connecting piece is broken (the connecting piece is too short or the spot welding with the pole piece is too low)
Nine, no flashing, low output voltage, can not bear the load
This kind of defect is mainly excluded from the bad cell (the cell originally has no voltage or low voltage). If the cell is bad, the self-consumption of the protection board should be checked 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 bad, the internal circuit of the PCB board is blocked, the via is blocked, MOS, IC damage, etc.).detailed analysis
The process is as follows:
(1) Use the black test lead of the multimeter to connect the negative electrode of the cell, the red test lead to connect the two ends of the FUSE and R1 resistors in turn, the Vdd, Dout, Cout terminals of the IC, and the P+ terminal (assuming the cell voltage is 3.8V), and analyze it segment by segment. These checkpoints should all be 3.8V. If not, there is a problem with this circuit.
1. The voltage at both ends of the FUSE has changed: check whether the FUSE is turned on. If the lead is the internal circuit of the PCB board, there is a problem with the FUSE (bad incoming material, overcurrent damage (MOS or IC control failure), There is a problem with the material (FUSE is burned out before the MOS or IC operates), then short-circuit the FUSE with a wire, and continue to analyze later.
2. The voltage across the R1 resistor has changed: check the R1 resistance value. If the resistance value is abnormal, it may be a virtual welding and the resistor itself is cracked. If there is no abnormality in the resistance value, there may be a problem with the internal resistance of the IC.
3. The voltage of the IC inspection terminal has been changed: the Vdd terminal is connected to the R1 resistor. If the Dout and Cout ends are abnormal, it is because the IC is soldered or damaged.
4. If there is no change in the previous voltage, check that the voltage between B- and P+ is abnormal, because the positive via of the protection board is blocked.
(2) The red test lead of the multimeter is connected to the positive electrode of the battery cell. After activating the MOS tube, the black test lead is connected to the MOS tube pins 2, 3, 6 and 7, and the P- terminal in turn.
1. If the voltage of MOS tube 2, 3, 6, 7 is changed, it means that the MOS tube is abnormal.
2. If the voltage of the MOS tube does not change and the voltage of the P- terminal is abnormal, it is because the negative via of the protection board is blocked.
10. No short circuit protection
1. There is a problem with the VM terminal resistance: a multimeter can be used to connect a test lead to the IC2 pin, and a test lead to the MOS pin connected to the VM end resistance, and confirm the resistance value. Check whether the resistor is soldered with IC and MOS pins.
2. IC and MOS abnormality: Because the over-discharge protection, over-current and short-circuit protection share a MOS tube, if the short-circuit abnormality is due to a problem with the MOS, this board should have no over-discharge protection function.
3. The above are faults under normal circumstances, and short-circuit abnormalities caused by poor IC and MOS equipment may also occur. For example, the BK-901 that appeared earlier, the delay time in the IC whose model is ‘312D’ is too long, causing the MOS or other components to be damaged before the IC performs corresponding action control. Note: The easiest and direct way to confirm whether the IC or MOS is malfunctioning is to replace the suspected components.
11. Short circuit protection without 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 set by the instrument is too short, or the load is not removed during the short-circuit inspection. For example, the test lead is not removed from the inspection end after short-circuiting the short-circuit test lead with the voltage range of the multimeter (the multimeter is equivalent to a load of several megabytes).
3. Leakage between P+ and P-, for example, there is rosin with impurities between the pads, yellow glue with impurities or the capacitance between P+ and P- is broken down, and the breakdown between ICVdd and Vss is broken. (The resistance value is only a few K to several hundred K).
4. Assuming that there is no problem with the above, maybe the IC is broken down. You can check the resistance between the pins of the IC.
12. Large internal resistance
1. Because the internal resistance of MOS is relatively stable and the internal resistance is large, the first suspect should be the components whose internal resistance is relatively simple to change, such as FUSE or PTC.
2. Assuming that the resistance value of FUSE or PTC is normal, check the resistance value of the via hole between the P+, P- pad and the component surface according to the structure of the protection board. Maybe the via hole has a micro-break phenomenon, and the resistance value is relatively large.
3. Assuming that there are no problems with the above, it is necessary to suspect whether the MOS is abnormal: first, confirm whether there is a problem with the welding; secondly, check the thickness of the board (whether it is simply bent), because bending may lead to abnormal welding of the pins; Put it 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.
Thirteen, ID disorder
1. The ID resistor itself is abnormal due to virtual welding, cracking or due to the failure of the resistance material: You can re-weld both ends of the resistor. If the ID is normal after re-welding, it is resistance welding. If it is cracked, the resistance will be cracked after re-soldering. open.
2. The ID via is not conducting: You can use a multimeter to check both ends of the via.
3. There is a problem with the internal circuit: scrape off the solder resist paint to see if the internal circuit is disconnected or short-circuited.