Are Lithium-ion batteries safe?
Lithium-ion batteries have helped to revolutionise technology development. However, they also have a reputation for volatility and bad press has meant that consumers and manufacturers have questioned their long-term viability. Jean-Louis Evans, managing director at TÜV Product Service offers this overview.
Electronic devices are becoming smaller with many power hungry features, resulting in the battery pack also becoming smaller, but at the same time requiring greater capacity. Such devices are often carried in people's pockets, increasing the potential safety hazard and risk of personal injury. To reduce that risk, education of the consumer plays a significant part by promoting the safe use of batteries and discouraging the purchase of non-genuine or counterfeit batteries and chargers.
While it is true that the increase in capacity of today's batteries, and end-user misuse, is part of the reason for the Li-ion battery's bad publicity, the manufacturing process has also been questioned. Many battery safety incidents involving notebook PCs have been linked to inadequate procedures relating to the avoidance of contaminates in production. As a result of the high number of incidents involving Li-ion batteries, there was an international move to improve testing and quality control through the introduction of standards including UL 1642 "Lithium Batteries", IEEE 1725 "IEEE Standard for Rechargeable Batteries for Cellular Telephones" and "UN Recommendations on the Transport of Dangerous Goods Manual of Tests and Criteria" (ST/SG/AC.10/11).
Another key catalyst was the introduction of the CTIA (Cellular Telecommunications and Internet Association) certification scheme, an industry led initiative in the USA that is based on the IEEE 1725 standard. Whilst US-centric, it has had a positive effect worldwide as manufacturers are unlikely to exclude themselves from the massive potential of the American market. The CTIA programme was devised in partnership with leading cellular network operators and required all products to undergo mandatory third-party testing and auditing, with certification categories covering cells, battery packs and power adapters, as well as complete cellular product systems. The CTIA requirements now also include another standard, IEEE 1625, which relates to notebook computers with GSM functionality that use Li-ion battery packs.
Manufacturers of Li-ion batteries now include internal protection devices, in addition to the protection circuits within the overall battery pack, to guard against excessive heat and pressure. These include a vent plate, which allows the safe release of gas, a positive temperature coefficient (PTC) so that a device safely trips at a
pre-determined current, and a separator, which once it reaches its defined temperature prevents the electrical current from flowing. Some prismatic batteries also have an additional feature, a thermal fuse which limits the current under fault conditions.
A protection circuit is also usually fitted within the battery pack that monitors the cell and prevents over-charge, over-discharge, and over-current. Also present is a temperature sensing device designed to invoke protective action in the event of over-temperature.
Lithium-ion batteries have a number of importance advantages:
But we have to balance that against the particular disadvantages of Lithium ion batteries:
The development of Li-ion technology has played a significant role in the pace of technology evolution and today's user demands that mobile devices and other technologies give them increased functionality with portability. Li-ion has helped manufacturers deliver on that.
While Li-ion batteries still have some disadvantages, their progressive development over the last few years has meant that these are far outweighed by the advantages. An improvement of manufacturing processes through the introduction of more robust standards, as well as increasing consumer understanding of how to respect these batteries, means that the safety of Li-ion has dramatically improved. It is a battery technology that has had a steep learning curve, now resulting in a good battery option that enhances all of our daily lives. Bad publicity and safety scares should be a thing of the past, at least for the non-counterfeit product.
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