Custom Lithium Ion Battery Pack

Lead-acid batteries leak and deform, what should we do

Mar 28, 2019   Pageview:90

1.battery leakage


Common leaks:


1) the seal between the upper cover and the bottom groove is not good or due to collision, and the sealant is cracked;


2)the safety valve seeps and leaks;


3)Leakage of acid at the terminals;


4)other parts showed acid leakage.


Inspection and treatment methods:


First check the appearance to find out where the acid leaks. Remove the cover to see if there is any leakage of acid leakage around the safety valve, and then open the safety valve to check the electrolyte inside the battery. After the above work is completed, if no abnormality is found, check for air tightness (into the air, pressurize and pressurize, observe whether the battery has bubbles or not, and there is a bubble indicating that there is acid leakage). Finally, during the charging process, observe whether there is any flow of electrolyte, if any, it is the reason for production. During the charging process, the flowing electrolyte should be exhausted.


2.Deformation


Fault phenomenon


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 in the positive electrode, and oxygen passes through the pores in the separator to reach the negative electrode. Perform oxygen reactivation on the negative plate:


2Pb+O2=2PbO+H2O+Q


PbO+H2SO4=PbSO4+H2O+Q


Heat is generated during the reaction. When the charging capacity reaches 90%, the oxygen generation rate increases, and the negative electrode begins to generate hydrogen gas. The increase of a large amount of gas is that the internal pressure of the battery exceeds the valve opening pressure, the safety valve is opened, the gas escapes, and the final performance is water loss.


2H2O=H2+O2


As the number of battery cycles increases, the water gradually decreases, and as a result, the battery appears as follows:


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


(2) The heat capacity is reduced, and the largest heat capacity in the battery is water. After the water loss, the heat capacity of the battery is greatly reduced, and the heat generated 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 becomes large, and the heat generation during charging and discharging increases. After the above process, the heat generated inside the battery can only be dissipated through the battery compartment. If the heat dissipation is less than the calorific value, the temperature rises, the battery's gassing overpotential decreases, and the gassing amount increases. A large amount of oxygen in the positive electrode passes through the "channel" and reacts on the negative surface, emitting a large amount of heat to cause the temperature to rise rapidly. The formation of a vicious circle leads to "thermal runaway" and deformation.


Fault checking and handling


A group of batteries (3) are deformed at the same time, and the voltage is checked first. If the voltage is basically normal. It should also measure the voltage of the single cell to determine whether it is short-circuited. If there is no short circuit, it means that the deformation is caused by overheating and "thermal runaway". The charging parameters of the charger should be checked. If the voltage is too high (above 44.7V), there is no overcharge protection or the turbulence conversion current is low. It is required to replace the charger.