Five Kinds Of Fault Judgments Common In Electric Vehicle Batteries

Five Kinds Of Fault Judgments Common In Electric Vehicle Batteries

Date:Mar 25, 2019

The manufacturing level of batteries for electric vehicles is uneven, and the difference in battery quality and performance is also quite large. The quality of the equipment in conjunction with the battery also affects the performance of the battery to varying degrees. The wide range of conditions of use also causes differences in the performance of electric vehicles, which may be understood by the user as the quality of the battery. Among the main components of electric vehicles, the failure rate of the battery is high. Some typical failure phenomena are listed below, and the inspection and treatment methods are introduced.

First, the battery plate sulfation

1, the phenomenon of failure

   Plate sulphation, also known as battery vulcanization, is the most common failure of lead-acid batteries, and many battery failures are also caused by this failure. The main performance of plate sulfation is as follows: the voltage rises rapidly during charging, the gas is precipitated prematurely, and the temperature rises rapidly; the voltage drops rapidly during discharge and the capacity is small.

2. Troubleshooting and handling of faults

   The reasons for the plate sulphation are summarized as follows:

  (1) The storage time is too long, the self-discharge rate is high, and maintenance and charging are not performed.

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

  (3) It is undercharged for a long time.

  (4) Overdischarge.

  (5) The concentration of electrolyte dissolved or added is too high

When the battery is sulphated, it should be repaired according to its severity. If the vulcanization is heavy, the battery needs to be charged and discharged by positive and negative pulses to return to normal. The specific method is as follows: first add pure water or a density of 1.05g/cm3 dilute sulfuric acid to the rich state, and then charge and activate it with a positive and negative pulse charger, the first charge should be sufficient for more than 12 hours, after filling Electric discharge, recharge, cumulative charging time to reach more than 24 hours, this is a common method of battery repair shop.

Home users can add water and charge with positive and negative pulse chargers, just like normal charging. For those with mild vulcanization, please use the positive and negative pulse charger to remove sulfur directly.

Second, the battery does not charge

1, the phenomenon of failure

  First check whether the connection of the charging circuit is reliable, check whether the connection between the connection and the plug is intact, and carefully check whether the socket and the plug have a "sparking" arcing phenomenon, and the wireless road is broken. Check the charger for damage and the charging parameters meet the requirements. Check if there is any dryness inside the battery, that is, if the battery is short of liquid. The plate should also be checked for sulfation. The sulfation of the plates can be determined by measuring the change in the terminal voltage by charge and discharge. During charging, the voltage of the battery rises particularly fast, and some single-cell voltages are particularly high, which is much higher than the normal value; the voltage drops particularly fast during discharge, and the battery does not store electricity or stores little power. When the above situation occurs, it can be judged that the battery is sulphated.

2. Troubleshooting and handling of faults

First connect the charging circuit firmly, and replace the charger if it is not normal. The dry battery should be supplemented with pure water or 1.050 sulfuric acid for maintenance charging and discharging to restore the battery capacity. If sulfation is found, the positive and negative pulse charge should be used to activate the recovery capacity. The maintenance charge after dry battery charging should be controlled to a maximum current of 1.8A and charging for 10-15 hours. The voltage of all three batteries is preferably 13.4V/only. If the voltage difference between the batteries exceeds 0.3V, the battery has been subjected to unsynchronized sulfation. For batteries that are sulphated, it is necessary to replace the entire battery or activate the battery with positive and negative pulses.

Third, the new battery voltage drops quickly

1, the phenomenon of failure

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

2. Troubleshooting and handling of faults

   Check that the meter shows that the voltage matches the battery capacity. When the voltage displayed by the meter and the battery capacity do not meet the above table, the manufacturer should be required to adjust. Check if the battery cable is reliable, if there is a short circuit and the connection is not reliable. Some are excluded. Check if the electric vehicle starting and running current is too large. If it is too large (the starting current is above 15A, the running current is more than 6A), adjust the controller current limit value or check and repair the motor. Check if the battery capacity is low. If it is low, the battery should be charged and discharged using positive and negative pulses.

Fourth, battery deformation

1, the phenomenon of failure

  Battery deformation is not sudden, there is often a process. The battery enters the high-voltage charging zone when it is charged to about 80% of the capacity. At this time, oxygen is first precipitated on the positive electrode plate, and oxygen passes through the hole in the separator to reach the negative electrode, and the oxygen reactivation reaction is performed on the negative electrode plate: 2Pb+O2= 2PbO+ heat

  PbO+H2SO4=PbSO4+H2O+ Heat generates heat during the reaction. When the charge capacity reaches 90%, the oxygen generation rate increases and the negative electrode begins to generate hydrogen. The increase of a large amount of gas causes the internal pressure of the battery to exceed the valve opening pressure, the safety valve opens, and the gas escapes, eventually showing a loss of water. 2H2O=2H2↑+O2↑ As the number of battery cycles increases, the water gradually decreases. As a result, the battery appears as follows:

(1) The oxygen "channel" becomes unobstructed, and the oxygen generated by the positive electrode easily reaches the negative electrode through the "channel".

(2) The heat capacity is reduced. The largest heat capacity in the battery is water. After the water is lost, the heat capacity of the battery is greatly reduced, and the generated heat causes the temperature of the battery to rise rapidly.

 (3) Due to the shrinkage of the ultra-fine glass fiber separator in the battery after water loss, the adhesion to the positive and negative plates is deteriorated, the internal resistance is increased, and the heat generation during charging and discharging is increased. After the above process, the battery

The heat generated inside can only be dissipated through the battery compartment. If the amount of heat dissipation is less than the amount of heat generated, the temperature rises. When the temperature rises, the battery's gassing overpotential decreases, the gassing amount increases, and a large amount of oxygen in the positive electrode passes through the "channel", reacts on the surface of the negative electrode, and emits a large amount of heat, causing the temperature to rise rapidly, forming a vicious circle, so-called "thermal runaway ", the final temperature reached 80OC or more, that is, deformation occurred.

 2. Troubleshooting and handling of faults

  When a group of batteries (3) are deformed at the same time, first check the voltage. If the voltage is basically normal, the single-cell voltage should also be measured to determine whether it is short-circuited. If there is no short-circuit, the deformation is caused by over-charging resulting in "thermal runaway". The charging parameters of the charger should be checked. High voltage (above 44.7V) no over-charge protection or low turbulence switching point current (different alloy grids require different switching currents, generally grids made of lead-calcium-tin-aluminum alloy The conversion current is small, which is 0.025-0.03C2A; while lead bismuth makes the battery conversion current of the grid made of gold larger than 0.03-0.04C2A, and the charger is required to be replaced. Only one or two of a group of batteries (3) Deformation only, the possibility of the following failures:

(1) The battery is inconsistently charged, causing deformation of some batteries caused by overcharging during charging. The reason for the inconsistency of the charge may be that there is a short circuit cell, or the user may discharge the battery test or self-discharge;

(2) It is the irreversible sulfation of the plates in some batteries, the internal resistance is increased, and the charging is heated and deformed;

(3) When some batteries are connected, the reverse pole causes charging and heating deformation. Check the discharge capacity and self-discharge characteristics of the undeformed battery. If there is no abnormality, it is not a battery problem.

  Measures to solve battery deformation are:

  ▲ Ensure that as much liquid is added as possible without leakage, to prolong or avoid the occurrence of “thermal runaway”;

  ▲ avoid internal short circuit or micro short circuit, and have a tendency to micro short circuit;

  ▲In the process of use, it should prevent the occurrence of over-discharge and make full power storage;

  ▲ Strictly check the charger, there must be no serious overcharge. At present, the ordinary three-stage charger on the market generally does not have the automatic power-off function. If you don't pay attention, it will overcharge, and it is easy to charge the battery. The positive and negative pulse charger will automatically switch to the floating state after being filled with a negative pulse. Even if the battery is overcharged for a long period of time, it will not damage the battery. Therefore, the positive and negative pulse charger is used to prevent the battery from being deformed and prevented. The best choice for battery hot.

  ▲At high temperature, it must be ensured that the battery is well cooled. Cooling measures should be taken or the charging time should be shortened, otherwise charging should be stopped. Fifth, the battery pack appears "unbalanced"

1, the phenomenon of failure

  The balance of series battery packs is a worldwide problem, and there will always be “backward” batteries in use. The reasons are various, production reasons, raw materials and reasons for use.

2. Troubleshooting and handling of faults

First, the battery is subjected to general maintenance charging, and then discharged with a current of 2 hours. During the discharge process, the voltage of the battery is continuously measured, and the "backward" battery with insufficient discharge capacity is selected for treatment. Add 1.050 of dilute sulfuric acid to just see the presence of flowing electrolyte, and continue charging for 12-15 hours. When charging, please pay attention to the temperature of the battery should not exceed 500C. After the end of charging, it was allowed to stand for 0.5-4 hours, and was discharged at a rate of 2 hours. During the discharge process, the value of the single-cell voltage is measured. If the discharge time does not reach the standard or the single-cell voltage reaches 1.6V, the discharge time is significantly different from the normal single-cell battery (the difference between the three months of the factory is 5 minutes).

In the above, the difference of 6 months is more than 8 minutes, the difference of 9 months is more than 10 minutes, and the difference of 13 months is more than 15 minutes. The above charging and discharging procedures need to be repeated until the requirements are met.

  If the battery capacity does not increase significantly after repeated charge and discharge cycles or is still about 0V low voltage, such batteries generally have a short circuit, or the active material is severely detached and softened, severe irreversible sulfation, etc., can not be repaired, should be scrapped. For those who meet the requirements, the battery can continue to be used, but under the constant pressure of 15V/only, the flow of electrolyte should be exhausted, the surface of the battery should be cleaned, the cap valve should be installed, and the PVC (or chloroform) adhesive should be used. The panels are bonded well.

If the positive and negative pulse charger is used for charging and maintenance, the voltage difference of each battery can be reduced to some extent.

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