5 kinds of common fault judgment of electric vehicle battery are briefly introduced

Electric vehicle battery manufacturing level is uneven, battery quality, performance difference is also quite large. The quality of the equipment with the battery also affects the performance of the battery to varying degrees. Different use conditions also cause differences in the performance of electric vehicles, which may be understood as battery quality problems in the eyes of users. In the important parts of electric vehicles, the failure rate of battery is high. Some typical failure phenomena are listed below, and the inspection and treatment methods are introduced.

Sulfurization of battery plate

1. Failure phenomenon

Plate sulphation, also known as battery vulcanization, is the most common fault of lead-acid batteries, and many battery failures are also caused by this fault. The important performance of plate sulphurization is: the voltage rises quickly when charging, the gas is precipitated prematurely, and the temperature rises quickly; Discharge voltage drop fast, small capacity.

2, fault inspection and treatment

The reasons for plate sulphurization are as follows:

(1) The storage time is too long, the self-discharge rate is high, and it is not maintained and charged.

(2) It is not charged in time after discharge.

(3) in the state of undercharging for a long time.

(4) Overdischarge.

(5) dry or added electrolyte concentration is too high.

When the battery is sulfurated, it should be repaired according to the severity of its degree. Vulcanization heavier, to the battery for positive and negative pulse charge and discharge, in order to return to normal. Specific means is: to battery first fill in pure water or density of 1.05 g/cm3 dilute sulphuric acid to the rich fluid state, with a positive and negative pulse charger to activate, charging to plenty more than 12 hours a day, for the first time put the electricity off, after full charge again, the cumulative charge time to achieve more than 24 hours, this is a useful method of battery repair shop.

For home users, you can add water and charge it with a positive and negative pulse charger, just like normal charging. For lighter vulcanization, please directly use the positive and negative pulse charger to remove sulfur.

Two, the battery does not charge into the electricity

1. Failure phenomenon

First of all, check whether the connection of the charging circuit is reliable, check whether the connection and the plug contact is intact, carefully check whether the socket and plug have the phenomenon of burning arc, whether the line is damaged or broken. Check whether the charger is damaged and whether the charging parameters meet the requirements. Check whether there is dry inside the battery, that is, whether the battery is seriously short of liquid. The plates should also be checked for sulfuration. Sulphurization of the plate can be determined by measuring the terminal voltage change of the charge and discharge. When charging, the voltage of the battery rises very fast, and some single voltage is very high, much beyond the normal value; When discharging, the voltage drops particularly fast, and the battery does not store electricity or stores little electricity. If the above situation occurs, it can be judged that the battery is sulfurized.

2, fault inspection and treatment

First, the charging loop is firmly connected. If the charger is not normal, it should be replaced. Dry batteries should be added with pure water or 1.050 sulfuric acid, maintenance charging, discharge to restore the battery capacity. If sulfuration is found, positive and negative pulse charging should be used to activate the recovery capacity. The maintenance and charging of the dry battery after adding liquid should control the maximum current of 1.8A and charge for 10-15 hours. The voltage of the three batteries is all above 13.4V/ only. If the voltage difference between the batteries is more than 0.3V, the battery has appeared out of sync sulfuration. For batteries that have sulfurated, replace the whole battery group or activate the battery with positive and negative pulses.

Three, the new battery voltage drops quickly

1. Failure phenomenon

The voltage drops quickly when the new battery is loaded and started.

2, fault inspection and treatment

Check whether the voltage displayed on the meter matches the battery capacity. If the relationship between the voltage and the battery capacity displayed on the meter does not conform to the above table, the manufacturer should be asked to adjust it. Check whether the battery connection line is reliable, there is no short circuit and connection is not reliable. If there is, it is excluded. Check whether the starting and running current of the electric vehicle is too large. If it is too large (the starting current is more than 15A, and the running current is more than 6A), the current limit value of the controller should be adjusted or the motor should be checked and repaired. Check whether the battery capacity is low, if low, the battery should use positive and negative pulse charge and discharge.

Four, battery deformation

1. Failure phenomenon

Battery deformation is not sudden, there is often a process. When the battery is charged to about 80% of the capacity, it enters the high voltage charging area. At this time, the oxygen is precipitated on the positive plate first, and the oxygen reaches the negative electrode through the hole in the partition plate. The oxygen is reactivated on the negative plate: 2PB +O2= 2PBO + heat

When PBO +H2SO4= PBSO4 +H2O+ heat reaction, heat occurs. When the charging capacity reaches 90%, oxygen generation rate increases, and hydrogen begins to appear in the negative electrode. The increase of a large amount of gas makes the internal pressure of the battery exceed the open valve pressure, the safety valve is opened, the gas escapes, and the final performance is water loss. 2H2O=2H2↑ +O2↑ With the increase of the number of cycles of the battery, the moisture gradually decreases, and the battery results in the following situation:

(1) The oxygen channel becomes unblocked, and the oxygen present in the positive electrode can easily pass through the channel to the negative electrode.

(2) The heat capacity decreases. The maximum heat capacity in the battery is water. After the loss of water, the heat capacity of the battery greatly decreases, and the heat generated increases the temperature of the battery quickly.

(3) Because of the shrinkage of the superfine glass fiber separator in the battery after water loss, the adhesion between the superfine glass fiber and the positive and negative plates becomes worse, the internal resistance increases, and the heat is increased in the process of charge and discharge. After the above process, the battery

The internal heat can only be dissipated through the battery groove, such as the heat release is less than the heat, that is, the temperature rise phenomenon. The temperature rises, so that the battery gas evolution overpotential is reduced, gas evolution increases, a large number of oxygen positive electrode through the channel, in the negative surface reaction, emit a large amount of heat, so that the temperature rises rapidly, the formation of a vicious cycle, namely the so-called thermal control, the final temperature reaches more than 80oC, that is, deformation.

2, fault inspection and treatment

When a group of batteries (3) is deformed at the same time, the voltage check should be done first. If the voltage is basically normal, the single voltage should also be measured to judge whether short circuit, no short circuit shows that the deformation is caused by overcharging thermal loss of control. Check the charging parameters of the charger. Voltage is high (higher than 44.7V above) no overcharging protection or the flow of the conversion point current is low (different alloy grid battery conversion current is not the same, generally say with lead calcium tin aluminum alloy grid battery conversion current is small, 0.025-0.03C2A; The lead and antimony make the gold grid battery conversion current is greater than 0.03-0.04C2A, the replacement of the charger is required. Only 1 or 2 batteries in a set of 3 are deformed, with the possibility of the following failure:

(1) is the battery charge is not consistent, charging caused by some battery overcharge caused by deformation. The reason for the charge inconsistency may be the existence of a short circuit single cell, or the user may test the battery discharge or self-discharge;

(2) some batteries appear plate irreversible sulfuration, internal resistance increases, charging heating deformation;

(3) It is the reverse pole of some batteries that causes charging heating deformation. Check the discharge capacity and self-discharge characteristics of the battery without deformation. If there is no abnormality, it is not a battery problem.

The measures to solve the battery deformation are:

▲ To ensure that the premise of no fluid leakage as much as possible, in order to extend or prevent the emergence of thermal runaway;

▲ Prevent internal short circuit or micro short circuit, and with micro short circuit tendency;

▲ In the process of use should prevent the occurrence of over-discharge, do enough electricity storage;

▲ Strictly check the charger, there should be no serious overcharge phenomenon, the ordinary three-section charger on the market, generally do not have automatic power off function, you do not pay attention to the overcharge, it is easy to charge the battery drum. The positive and negative pulse charger because of negative pulse discharge, after full will automatically turn to the floating charging state, even if the charge for a longer period of time will not damage the battery, so the use of positive and negative pulse charger is to prevent the battery deformation, prevent the battery hot best choice.

▲ Charging at high temperature, must ensure good heat dissipation of the battery. Take measures to cool down or reduce the charging time, otherwise, the charging should be stopped. Five, the battery pack is not balanced

1. Failure phenomenon

The equilibrium of series battery group is a worldwide problem. There are always backward batteries in the process of use. Its reason is various, have production reason, also have raw material reason and use reason and so on.

2, fault inspection and treatment

The battery is first charged for general maintenance and then discharged with a 2-hour rate current. In the discharge process, the battery voltage is constantly measured, and the backward battery with insufficient discharge capacity is selected for treatment. First add 1.050 dilute sulfuric acid until just see the presence of flowing electrolyte, and then continue to charge for 12-15 hours. When charging, pay attention to the temperature of the battery should not exceed 500C. After charging, let it stand for 0.5-4 hours and then re-discharge at a rate of 2 hours. In the discharge process, measure the value of the single cell voltage, if the discharge time is not up to the standard or the single cell voltage to 1.6V, the discharge time and the normal single cell battery difference is large (factory three months difference of 5 minutes

, 6 months difference of more than 8 minutes, 9 months difference of more than 10 minutes, 13 months difference of more than 15 minutes), it is necessary to repeat the above charge and discharge procedures until it meets the requirements.

If the repeated charging and discharging cycle, the battery capacity does not rise significantly or is still about 0V low pressure, the battery generally has a short circuit, or the active material seriously off softening, serious irreversible sulfuration, etc., can not be repaired, should be scrapped. To meet the requirements of the battery can continue to use, but should be in constant pressure 15V/ only charging conditions, drain the flow of electrolyte, wipe the battery surface, install a cap valve, with PVC (or chloroform) adhesive panel bonding.

If the positive and negative pulse charger is used to charge and maintain the battery, the voltage difference of each battery can be reduced to a certain extent.