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Lead is a toxic metal that can enter the body by inhalation of lead dust or ingestion when touching the mouth with lead-contaminated hands. If leaked onto the ground, the acid and lead particulates contaminate the soil and become airborne when dry. Children and fetuses of pregnant women are most vulnerable to lead exposure because their bodies are developing. Excessive levels of lead can affect a child’s growth, cause brain damage, harm kidneys, impair hearing and induce behavioral problems. In adults, lead can cause memory loss and lower the ability to concentrate, as well as harm the reproductive system. Lead is also known to cause high blood pressure, nerve disorders, and muscle and joint pain. Researchers believe that Ludwig van Beethoven became ill and died from lead poisoning.
Lithium-ion has a high specific energy and even though safe, high usage by millions of consumers is bound to generate failures. In 2006, a one-in-200,000 breakdown triggered a recall of almost six million lithium-ion packs. Heat-related battery failures are taken very seriously, and manufacturers choose a conservative approach. Let’s examine this closer.
Batteries are safe, but precaution applies when touching damaged cells and when handling lead acid systems that have access to lead and sulfuric acid. Several countries label lead acid as hazardous material, and rightly so. Let’s look at the hazards if not properly handled.
The sulfuric acid in a lead acid battery is highly corrosive and is potentially more harmful than acids used in other battery systems. Eye contact can cause permanent blindness; swallowing damages internal organs that can lead to death. First aid treatment calls for flushing the skin for 10 to 15 minutes with large amounts of water to cool the affected tissues and to prevent secondary damage. Immediately remove contaminated clothing and thoroughly wash the underlying skin. Always wear protective equipment when handling the sulfuric acid.
Cadmium, which is used in nickel-cadmium batteries, is considered more harmful than lead if ingested. Workers at NiCd manufacturing plants in Japan have been experiencing heath problems from prolonged exposure to the metal, and governments have banned the disposal of nickel-cadmium batteries in landfills. The soft, whitish metal that occurs naturally in the soil can damage kidneys. Cadmium can be absorbed through the skin by touching a spilled battery. Since most NiCd batteries are sealed, there are no health risks in handling them. The caution applies when working with an open battery.
Nickel-metal-hydride is considered non-toxic and the only concern is the electrolyte. Although toxic to plants, nickel is not harmful to humans. Lithium-ion is similarly benign — the battery contains little toxic material. Nevertheless, caution is required when working with a damaged battery. When handling a spilled battery, do not touch your mouth, nose and eyes, and wash your hands thoroughly.
Keep small batteries out of children’s reach. Children younger than four are most likely to swallow batteries, and the most common types ingested are button cells. The battery often gets stuck in the esophagus (the tube that passes food) and the electrical current burns the surrounding tissue. Doctors often misdiagnose the symptoms, which can show as fever, vomiting, poor appetite and weariness. Batteries that make it through the esophagus often move through the digestive tract with little or no lasting damage. The concern of a parent is not only to choose safe toys, but also to keep small batteries away from young children.
Over-charging a lead acid battery can produce hydrogen-sulfide. The gas is colorless, very poisonous, flammable and has the odor of rotten eggs. Hydrogen sulfate also occurs naturally during the breakdown of organic matter in swamps and sewers; it is also present in volcanic gases, natural gas, and some well waters. Being heavier than air, the gas accumulates at the bottom of poorly ventilated spaces. Although noticeable at first, the sense of smell deadens and potential victims may be unaware of its presence. As a simple guideline, hydrogen sulfide becomes harmful to human life if the odor is noticeable. Turn off the charger, vent the house and stay outside until the odor disappears. To learn about potential hazards when incorrectly charging Li-ion, read Lithium Safety Concerns.
During a thermal runaway, the high heat of the failing cell may propagate to the next cells, causing them to become thermally unstable also. A chain reaction can occur in which each cell disintegrates on its own timetable. A pack can thus be destroyed in a few seconds or over several hours as each cell is being consumed one by one. To increase safety, packs should include dividers to protect the failing cell from spreading to the neighboring one.
Charging batteries in living quarters should be safe. This also applies to lead acid. Ventilate the dwellings regularly as you would a kitchen when cooking. Lead acid produces some hydrogen gas but the amount is minimal when charged correctly. Hydrogen gas is explosive and one would need a concentration of 4% to create an explosion. This level would only be achieved if large lead acid batteries were charged in a sealed room.
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