EIGHT Shocking Reasons Why Lead-Acid Batteries Explode
By the author of the Amazon Bestseller Book 'Batteries Demystified', Podcaster, & Expert in Lead Acid Battery Manufacturing Processes and Machines
In today’s article, I shall outline the eight primary reasons for the explosion of lead-acid batteries.
Lead-acid batteries are very safe, and there is usually no reason for a battery to catch fire or explode due to a fault in their chemistry. There are a few instances of fire due to thermal runaway in sealed, maintenance-free lead-acid batteries. However, the vented type flooded electrolyte lead-acid batteries are relatively much safer, with very few instances of explosion or fire.
The cases of fires in electric vehicles that use lithium-ion batteries have put the spotlight on battery fires and safety-related issues.
A lead-acid battery can explode for any of the following reasons:
The battery can explode if the vent holes of the vent plugs are clogged due to the battery being used in a dusty or dirty environment. Batteries with such clogs in the vent plug holes shall not allow gases to escape, leading to a pressure buildup that can result in an explosion.
The battery can explode if it is subject to an overcharge, i.e., continuously and fully charged. When a battery is fully charged, the active material has been fully converted. It has become sponge lead on the negative and lead dioxide on the positive. In such a condition, no lead sulphate active material can be converted chemically on both the positive and the negative plates. The electrical energy fed by the charger, which is supposed to be converted to chemical energy, is converted to heat energy. The electrolyte gets heated, and the evolving explosive hydrogen gas generated builds up the pressure under the vent plugs, causing the vent plugs to pop up or build up sufficient pressure to explode the battery.
The third reason is if the battery is charged using an incorrect charger. When the battery is connected to a charger designed for a larger capacity battery, the charger starts charging the battery at a current higher than the recommended level. In such cases, battery life is affected, and the active plate material begins to shed, creating an internal short. The internal short causes heat and an explosion. In this case, the internal short is not due to a manufacturing defect but to an incorrect charger selection.
The fourth reason is that the battery can explode if sources of static electricity cause a spark in its vicinity. Also, naked flames, welding sparks, or any other sparks near the batteries, especially when the batteries are on charge, can cause a fire or explosion. As and when batteries are on charge, hydrogen gases are evolved.
Hydrogen gas is very flammable, yielding explosive mixtures with air and oxygen. Since hydrogen gas is flammable, a spark with oxygen from the atmosphere can lead to a fire and an explosion of the battery. Hence, even smoking cigarettes is not recommended in rooms where batteries are on charge.
The fifth reason is the risk of battery explosion if the batteries are charging in a room with improper ventilation. When batteries are on charge, hydrogen and oxygen are both evolved as gases. They do recombine to form water, but not fully. If the hydrogen gas is evolved to such an extent that the concentration of hydrogen gas exceeds 4%, it can cause an explosion of the battery. Hence, batteries must be charged in an atmosphere where the gases can escape.
The manufacturers usually recommend that battery charging areas or rooms have adequate ventilation with at least six air changes per hour. If there is an exhaust fan in the battery room, there must be an air inlet diagonally opposite the exhaust fan's location. This ensures that fresh air continues to enter and is exhausted along with the hydrogen that is generated in that room.
The sixth reason is if a battery of a smaller than recommended size or lower AH capacity is used. At times, due to the non-availability of correct capacity batteries or cost considerations, batteries of lower capacities are fitted to equipment or material handling vehicles. In such cases, the charger, being of a much larger capacity than required by the battery, tends to overcharge the battery, heat it, cause bubbling and gassing, and possibly lead to an explosion of the battery due to pressure buildup within the battery container.
Hence, there are instances where, for example, if you need an N70 battery and it is not available at the dealer, you may end up instructing the dealer to fit an N50 battery, but this is not recommended.
Similarly, in forklifts where a 48V 553AH battery is required, due to cost considerations, sometimes the user says, "Please give me a 48V 450AH or a 48V 400AH battery." The voltage is the same, but the AH capacity is substantially reduced, and you are using a charger meant for a 553AH battery for a 400 or a 450AH battery. This is not recommended, and in such situations, the batteries can explode.
The seventh reason is that the battery can explode if the terminals are shorted externally with any metal object or conducting substance. A loose connection at the terminal ends can cause sparks and also lead to an explosion or fire.
The last reason, the eighth reason, is that the battery can explode if it has an internal short due to a manufacturing defect.
A missing separator or a lead run between the plates, or premature shedding of the active material, can cause this internal shorting if overlooked during assembly. However, such a manufacturing defect is a rare occurrence, as a quality control inspector can easily detect it during the final stage of battery assembly inspection. Suppose the manufacturer does not detect the same fault for any reason. In that case, the fault in the manufactured product typically manifests itself within 10-15 days or, at most, within a month of battery use. Hence, this reason is infrequent and not a very common cause of an explosion of a lead-acid battery.
Based on the details I provided, it is clear that lead-acid battery chemistry is safe and not prone to fires due to thermal runaway, a phenomenon typically associated with lithium-ion battery chemistry. Thus, lead-acid batteries are comparatively much safer than lithium-ion batteries.
Almost all reasons for mishaps in lead-acid batteries are external causes, and thus, abuse, misuse, or neglect of the batteries are the primary reasons for lead-acid battery fires or explosions. Therefore, proper use and maintenance of lead-acid batteries guarantee safe performance without any cause for worry.
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