Although it has become a consensus that lead-acid batteries are gradually being replaced by lithium-ion batteries (especially lithium iron phosphate batteries whose voltage platform can be perfectly matched), lead-acid batteries are still used in many occasions. There are many factors that lead to this, such as price, size, simplicity, etc. Safety is also an important factor: most people think that lead-acid batteries are absolutely safe secondary batteries, and lithium-ion batteries are too unsafe. SES Power admits that lead-acid batteries are safer than lithium-ion batteries, but in terms of the entire system (electronic monitoring, structural design, etc.), lithium-ion batteries are actually very safe, and can even be achieved with the assistance of BMS. Many preventive actions, such as our fully intelligent lead-acid replacement products (12V100Ah, 12V200Ah), high-current (2000A) start-up lithium battery, UPS high-voltage lithium battery system (up to 860V), 3Kw~20Kw off-grid lithium battery storage Energy system, base station communication backup battery system (standard 19 inches) and other products are almost all implemented as updated products of lead-acid batteries. In fact, lead-acid batteries are also at risk of fire and explosion. Let's first look at a report:

　　On the afternoon of August 3, local time, the River's Edge RV park in the United States exploded because of a lead-acid battery system. Relevant personnel rushed to the park and found the container with the top of the system lost after the explosion. Residents near the park reported hearing the sound of the explosion.

　　Although the accident caused damage to the energy storage system and serious deformation, luckily no casualties were caused. Judging from the situation at the scene, the accident damaged the nearby laundromat and surrounding trees, and even the roofs of residents were scattered with broken branches. It is understood that the project was completed in 2016 and has only been used for eight years.

　　Park superintendents say the lead-acid battery system, which was installed about four years ago, is used as a backup energy source to prevent the park's solar system from failing. Generally speaking, the probability of explosion of lead-acid batteries is very low when used properly, but it is not 100% non-explosive for lead-acid batteries.

　　A retired photovoltaic system designer in the United States said: From the photos, the battery module is still installed in the container, so it is guessed that there may be a problem with ventilation at that time. He said the ceiling is a natural weak point, and when there is a danger of explosion, it is normal for the roof to have weak points in order to dissipate the stress upwards, but the bulge on both sides in the photo shows that this is not the case.

　　The results of the investigation report after the incident showed that due to the continuous and irregular charging of the lead-acid battery, the water in the electrolyte was decomposed into hydrogen and oxygen and evaporated. Coupled with the lack of maintenance, the battery plates were overheated and damaged internally. There was no ventilation system, so flammable hydrogen gas accumulated, and eventually sparks from an unknown source ignited the accumulated hydrogen, which eventually led to an explosion.

　　When the lead-acid battery is overcharged, the water in the battery electrolyte will be electrolyzed, and hydrogen and oxygen will be produced after electrolysis, which are flammable and explosive gases. Earlier in 2022, the tugboat's battery bay in Lazaret exploded when the Canadian company's tugboat, the Risco Warrior, docked the barge Western Carrier at the Mellersh Point dock in Bute Inlet, British Columbia. The explosion caused structural damage to the ship and two crew members on board were slightly injured; on September 4, 2021, the first phase of the Moss Landing project in California, USA, due to the activation of the battery's water cooling system, about 7% of the project's battery modules and other The system equipment caused losses, and the accident did not cause casualties or affect the surrounding communities.

　　SES Power engineers believe that whether it is a lithium battery or a lead-acid battery, there is a risk of thermal runaway of the battery. The space-level detection and early warning can no longer meet the current speed of battery thermal runaway, and Andun engineers have developed an aerosol automatic fire extinguishing device specially designed for battery PACK-level protection, so that hidden dangers are extinguished in the budding stage, and lead-acid, Lithium battery safety.

　　Of course, to prevent the recurrence of such accidents, we must know its principle in order to carry out accurate and safe protection actions:

　　The new lead-acid battery has higher terminal voltage and lower internal resistance due to more chemical reaction substances, while the old lead-acid battery has lower terminal voltage and higher internal resistance. Generally, the internal resistance of a new 12V lead-acid battery is 0.015-0.018 ohm, while the internal resistance of an old lead-acid battery is more than 0.085 ohm. The charging voltage at both ends of the new lead-acid battery will be higher than the charging voltage at both ends of the new lead-acid battery, resulting in a situation where the new lead-acid battery is not fully charged, and the old lead-acid battery has a serious overvoltage.

　　In the discharge state, since the capacity of the new lead-acid battery is larger than that of the old lead-acid battery, the old lead-acid battery will be overdischarged, and even the phenomenon of reverse polarity of the old lead-acid battery will eventually form the side effect of bulging. It will deplete the power of the new lead-acid battery, and it will also cause the internal voltage to be unstable, and there is a danger of overusing the old lead-acid battery.

　　What are the causes and phenomena of lead-acid batteries that cause explosions?

　　1: The internal pressure of the lead-acid battery is too high, causing the lead-acid battery shell to explode

　　From the working principle of lead-acid lead-acid battery, it can be known that during the charging process, especially at the end of charging, water is decomposed into hydrogen and oxygen due to overcharging, short circuit, severe vulcanization and the sharp rise of electrolyte temperature during charging, which will eventually lead to a large amount of water evaporation. At this time, if the vent hole of the filler cap is blocked (too much gas can't overflow), the pressure inside the lead-acid battery will rise very high.

　　On the surface, it will cause the lead-acid battery tank to deform first. When the internal pressure reaches a certain pressure, it will burst from the junction of the lead-acid battery tank cover or other weak points. This is a physical process. When the internal pressure of the lead-acid battery is higher than 0.25MPa, the lead-acid battery bursts, and the burst position is located at the joint of the hot air of the tank cover or the corner where the stress is concentrated.

　　2: The lead-acid battery formed by hydrogen encountering an open flame explodes

　　The explosion limit of H2 and O2 mixed gas: H2 accounts for 4%-74% of the mixed gas volume. If 80% of the overcharge is used for water electrolysis, the H2 content inside the lead-acid battery is greater than the explosion range. When the hydrogen content in the lead-acid battery or in the air accumulates to the explosion limit, it will explode when encountering an open flame. , which is a chemical reaction.

　　The study found that the explosion of lead-acid batteries is a branched explosion reaction. Too many such explosions occur in the case of overcharging. If there are virtual solder joints in the internal poles, through-wall welding, etc. of the lead-acid battery, the explosion probability of the lead-acid battery is higher.

　　A qualified lead-acid battery will not have a self-heating explosion reaction under normal use conditions. When the charging voltage of the 12V lead-acid battery is higher than 14.4V, explosion may occur under the condition of the presence of fire at the same time. The study examined vehicles with lead-acid battery explosions and found that most of the voltage regulators were defective, causing the lead-acid battery to be severely overcharged.

　　3: The structure is not strong, resulting in the generation of sparks

　　In fact, the above two conditions are basically caused by the poor internal quality of the lead-acid battery and the unreasonable charging. If there is no external cause of Mars, the hydrogen gas mixture cannot be ignited. Therefore, the exact process of lead-acid battery explosion is: due to the blockage of the lead-acid battery vent, the lead-acid battery bursts first, and the burst causes the lead-acid battery to vibrate.

　　In fact, lead-acid batteries have gradually faded out in many industries. SES Power recommends customers to use lithium-ion batteries as much as possible - because they are more environmentally friendly, efficient and lightweight. However, the safety of lithium-ion batteries is indeed lower than that of lead-acid batteries, so we suggest that customers should focus on the design capabilities, experience accumulation, high-quality batteries, in quality control and other aspects, price is definitely not the only focus, and SES Power has a deep understanding of this.