The theme for this issue of NETA World is electric vehicle (EV) charging stations. EV vehicles are either wholly driven off battery power or, in the case of a hybrid, driven with battery and supplemented with a gas internal combustion engine. Let’s review some of the safety issues associated with batteries.
One major concern when working with or around batteries is a terminal short. A terminal short is caused when the positive and negative terminals are connected to each other via a conductive item. If terminals are shorted against each other for a sufficient period of time, this can cause an overload in the battery and potentially a spontaneous failure due to overheating.
Additionally, the shorting of two terminals on a battery can generate sparks, which can cause flammable gasses to ignite or explode. Even if the battery does not fail due to the connection of the two terminals, the life of the battery is significantly degraded due to the heavy workload placed upon it and the significant heating that has occurred.
The components that make up a battery are another primary concern.
A very common wet-type battery contains a heavy metal (lead) and an acid (sulfuric). If a lead-acid battery is unsealed, it can potentially spill, causing acid burns on the skin. Lead is also hazardous when ingested in large enough quantities. Other batteries contain different chemicals such as lithium, cadmium, bromide, and many other heavy metals that can be health hazards if ingested, injected, or absorbed in large enough quantity.
If a lead-acid battery, a type commonly found in substations, is overcharged, the battery will produce hydrogen. Hydrogen is highly flammable and has been known to easily ignite when exposed to a spark. Overcharging creates high heat, which causes additional off-gassing and can created an incidental spark, causing the hydrogen gas to ignite and the battery to explode.
To prevent overcharging, batteries should be closely monitored during the charging process. A trickle charger can be used to prevent overheating of the battery during the charging process. Using a trickle charger will take longer to achieve a full charge of the battery, but it will make the charging process safer and more manageable. Trickle charging also prolongs the lifecycle of the battery, as opposed to a fast charge, which can shorten the life of the battery.
One precaution that can be taken when working around a large number of lead-acid batteries is to ensure there is adequate ventilation. This will prevent the buildup of hydrogen gas within a storage room. Non-sparking (brass) tools should be used when performing any work on or near batteries that have the potential to off-gas hydrogen.
Wet-type (acid) batteries have also been known to fail when an interior plate becomes loose or breaks. The plate can then contact other plates within the battery, and if they are opposing metals, the plates can cause a buildup of heat within the battery case. In the presence of enough hydrogen and oxygen, this heat can cause an explosive failure of the battery.
Most electric vehicles use lithium-ion or lithium-polymer batteries. These are the same batteries found in most commonly rechargeable items, including cellular phones, tablets, and laptops. They are generally very safe and unlikely to fail, but when they do fail, it is spontaneous and will present a significant fire and explosion hazard. Like lead-acid batteries, damage can be caused by improper use or storage and overcharging. These batteries can be physically damaged during an impact, such as dropping or during a vehicle crash. Exposure to fire or excessively high or low temperatures can also damage a lithium-ion battery.
As with most tools, always inspect the battery and the charger prior to recharging any type of battery. Inspect for correct terminal connections, bulging of the battery case, worn or missing insulation, and proper settings. Use care when connecting terminals to the charger or inserting a plug. Ensure that the terminals are clean, the connectors or alligator clips grip tightly and make good contact, and that there are no obstructions in a charging port.
Electric vehicles may have proprietary connectors, so ensure you are using the correct connector or adapter. As with fueling a combustible engine, don’t leave the battery or vehicle unattended if fast charging, when damage is most likely to occur. Wear the proper personal protective equipment (PPE) while charging the battery, if required.
For any battery, always read and follow manufacturer’s guidance on how to extinguish a battery fire, which could include using ABC dry chemical extinguishers, Class D fire extinguishers (for lithium-metal), dirt, or sand.
Care should also be undertaken when moving any battery. Unsealed wet cell batteries may spill acid if up-ended, and the spilled acid could potentially burn an unsuspecting employee if they are not wearing the appropriate PPE. In addition, a battery can be extremely heavy due to the contents being lead or other heavy metal, and lifting a battery improperly can cause injury. Be careful, and use proper lifting techniques when lifting or moving a battery.
Paul Chamberlain has been the Safety Manager for American Electrical Testing Co. LLC since 2009. He has been in the safety field since 1998, working for various companies and in various industries. Paul received a BS from the Massachusetts Maritime Academy.