Summary of abnormal causes of lithium battery and fault judgment

A summary of the causes of abnormal 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 everyone.

 

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 electrolyte conductivity is low; f. Not well equipped; g. Porosity of the diaphragm is small; h. Adhesive aging → attached material falls off; i. The core is too thick (not dried or the electrolyte is not penetrated) j. The volume is not fully charged when the volume is divided; k. Positive and negative electrodes The material has a small specific capacity.

 

 

2. High battery internal resistance

Causes: a. Welding of the negative electrode and the tab; b. Welding of the positive electrode and the tab; c. Welding of the positive electrode and the cap; d. Welding of the negative electrode and the shell; e. The contact between the rivet and the pressure plate is large. ; 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, battery voltage is low

 cause:

 

a. Side reactions (decomposition of the electrolyte; impurities in the positive electrode; water); b. Incomplete formation (the SEI film is not formed safely); c. The leakage of the customer's circuit board (refers to the battery sent back by the customer after processing); d .The customer fails to spot welding as required (the battery cell processed by the customer); e. burr; f. micro short circuit; g. dendrite in the negative electrode.

 

4, super thick

a. Weld leakage; b. Electrolyte decomposition; c. Undried moisture; d. Poor cap sealing; e. The shell wall is too thick; f. The shell is too thick; g. The core is too thick (too much material attached) ; The pole piece is not compacted; the diaphragm is too thick).

 

5. Abnormal battery formation

a. Not well formed (the 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 positive electrode has more material and the negative electrode has less material; e . Air leakage in the cap and welding seam; f. The electrolyte is decomposed and the conductivity is reduced.

 

6, the battery explodes

A. The sub-capacitor is faulty (causing overcharge); b. The diaphragm closing effect is poor; c. Internal short circuit.

 

7, battery short circuit

A. Material dust; b. The shell is broken; c. The ruler is scraped (the diaphragm paper is too small or not well-pad); d. The winding is uneven; e. Not wrapped properly; f. The diaphragm has a hole; g. Burr

 

8. The battery is disconnected

a) The pole lug and the rivet are not welded well, or the effective solder joint area is small; b) The connecting piece is broken (the connecting piece is too short or the welding is too low when spot welding with the pole piece)

 

Lithium battery protection board failure judgment

 

common bad analysis of lithium battery protection board

One, no flash, low output voltage, no load

This type of defect should first eliminate the defective battery cell (the battery cell originally has no voltage or the voltage is low). If the battery cell is defective, the self-consumption of the protection board should be checked to see whether the self-consumption of the protection board is too large and the battery 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.). detailed analysis

 

The 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), and analyze it 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), then use a wire to short the FUSE, and continue to analyze later.

 

2. The voltage at both ends of the R1 resistance has changed: check the resistance value of R1. If the resistance value is abnormal, it may be a false 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 has changed: the Vdd terminal is connected to the R1 resistor. The Dout and Cout terminals 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, it is because the positive through hole of the protection plate is blocked.

 

(2). Connect the red test lead of the multimeter to the positive electrode of the battery. After activating 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 pins 2, 3, 6 and 7 of MOS tube is changed, it indicates that the MOS tube is abnormal.

 

2. If the MOS tube voltage is unchanged and the P-terminal voltage is abnormal, it is because the negative via of the protection plate is blocked.

 

Two, short circuit without protection

1. There is a problem with the VM terminal resistance: a multimeter can be used to connect one test pen to IC2 pin, and one test pen to the MOS pin connected to the VM terminal resistor to confirm its resistance value. Check whether the resistance and IC, MOS pins are soldered.

 

2. IC and MOS malfunction: Because the over-discharge protection and over-current and short-circuit protection share a MOS tube, if the short-circuit malfunction is due to a MOS problem, the board should have no over-discharge protection function.

 

3. The above are defects under normal conditions, and there may also be short circuits caused by poor IC and MOS equipment. For example, in the BK-901 that appeared in the previous period, the delay time in the IC with the model number ‘312D’ was too long, which caused the MOS or other components to be damaged before the IC took the corresponding action. Note: The easiest and most direct way to confess whether the IC or MOS is malfunctioning is to replace the suspected components.

 

Three, short circuit protection without self-recovery

1. The IC used in planning does not originally have a 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. For example, the test leads are not removed from the test end after the short-circuit test leads are short-circuited with the multimeter voltage file (the multimeter is equivalent to a load of several megabytes).

 

3. Leakage between P+ and P-, such as impurity rosin between pads, impurity yellow glue or P+, P- capacitance breakdown, ICVdd to Vss breakdown. (The resistance is only a few K to a few hundred K).

 

4. Assuming that the above is all right, maybe the IC is broken down, you can check the resistance between the pins of the IC.

 

Four, large internal resistance

1. Because the internal resistance of MOS is relatively stable and large internal resistance occurs, the first suspicion should be FUSE or PTC components whose internal resistance is relatively simple to change.

 

2. Assuming that the resistance value of FUSE or PTC is normal, check the resistance value of the via hole between the P+ and P- pads and the component surface depending on the structure of the protection board. Perhaps 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 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 is abnormal

1. The ID resistor itself is abnormal due to virtual welding, cracking or because the resistance material is not closed: the two ends of the resistance can be welded from the beginning, if the ID is normal after rewelding, the resistance is virtual welding, if it is cracked, the resistance will be cracked after the rewelding open.

 

2. The 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.