c is common, but because people do not know much about the use of batteries, there will be some misunderstandings. Especially in recent years, the application of electric vehicles has become more and more extensive, but due to improper use of lead-acid batteries, explosion accidents have occurred, causing great losses to people's lives and property safety. This article will analyze the root cause of battery explosion from the working principle of lead-acid battery, for your reference.

1. Working principle of lead-acid battery

The positive electrode active material of the lead-acid battery is PbO 2 , the negative electrode active material is spongy metal Pb, and the conductive medium is dilute sulfuric acid (electrolyte). During the charging and discharging process of the battery, the following reactions will occur on the positive and negative plates, converting the electrical energy into chemical energy stored in the battery or converting the chemical energy into electrical energy for supply to the load.

The composition of the precipitated gas when the lead-bismuth alloy battery is charged with the change of voltage is shown in Table 1. During the charging process of the battery, a combustible mixed gas is easily formed inside and around the battery. If the vent hole is not smooth, a high voltage is easily formed in the battery.

During the charging and discharging process of the battery, the internal resistance generates heat, which causes the temperature of the electrolyte to rise, and then some of the water becomes water vapor. If the battery vent hole is unblocked, the water vapor will be discharged outside the battery. In the long run, the battery will be dehydrated, otherwise a certain internal pressure will be formed in the battery.

2. Three cases of lead-acid battery explosion

2.1 The internal pressure is too high and causes an explosion

At the end of the lead-acid battery charging, water decomposes into hydrogen and oxygen. At the same time, short circuit, severe sulfurization and a sharp rise in electrolyte temperature will cause a large amount of water to evaporate. If the vent hole is clogged, the internal gas of the battery will be too much to overflow. As a result, the internal pressure and temperature of the battery are too high, which first causes deformation of the battery case. When the internal pressure is concentrated to a certain extent, it will burst from the battery slot cover joint or other weak places, which is a physical process.

2.2 Hydrogen encounters battery explosion caused by open flame

The explosion limit of the H2 and O2 mixed gas is 4% to 96% of the volume of the mixed gas, and the explosion limit of the H2 and air mixture is 4% to 74% of the volume of the mixed gas. When the hydrogen content generated by the battery accumulates to the explosion limit, an explosion occurs when exposed to an open flame, which is a chemical reaction. It is found that the explosion of the battery belongs to the branch explosion reaction. Most of the explosions occur in the case of over-charging. If there is a virtual solder joint in the internal pole and the wall welding of the battery, the explosion probability of the battery is high. A qualified battery will not undergo a self-heating explosion reaction under normal conditions of use.

2.3 first burst after the explosion

Due to the blockage of the battery vent, the battery first bursts, the battery causes the battery to vibrate, and the pole column wiring does not produce a spark, which forms an explosion.

3. Preventive measures

It can be known from the above explosion mechanism of the lead-acid battery that the explosion of the battery should be prevented from the prevention of the formation of the explosive mixed gas and the elimination of the open flame during use. The specific measures are as follows:

a) The battery charging room is well ventilated and has no open flame;

b) use a matching charging device, but charge;

c) The cable connection should be firm and reliable to avoid sparks caused by looseness;

d) the vent of the battery remains unobstructed;

e) Whether the output voltage of the regulator (or integral alternator) is within the specified range, generally the gasoline vehicle does not exceed 14.4V, and the diesel vehicle does not exceed 28.8V.