Lithium-Ion Chemistry is the Power Behind Today’s Laptop Batteries

Friday, March 10, 2017

If you own a laptop computer, chances are very very good that it is probably powered by a lithium-ion (Li-ion) battery. This battery type has found application in a wide variety of consumer electronics, including PDAs and cell phones. They have gained widespread popularity due to economic and technical reasons, particularly their high charge to weight ratio.

Lithium-ion batteries have replaced the nickel-cadmium (NiCd) batteries that were first used to power laptop computers and the nickel-metal hydride (NiMH) batteries that superseded the NiCd laptop battery technology. They have dominated today’s rechargeable battery market for laptop computers because they are much lighter than the other types of laptop batteries, they retain their charge longer than the other technologies and because they do not suffer from the memory effect phenomenon. A typical lithium-ion battery has two times the energy density of a standard nickel cadmium battery. Additionally, lithium-ion batteries have a single cell voltage of 3.6 volts as compared to 1.2 volts per cell of nickel-cadmium batteries.

However, the disadvantages associated with lithium-ion batteries include: the possibility that a failed battery pack can ignite under adverse conditions, they are more sensitive to high temperature environments than the other battery technologies in their ability to retain their charge, they may fail if they are completely discharged, and the inherit chemistry of the battery leads to degradation with age as opposed to the stronger correlation between battery failures and charge/discharge cycles of the older battery chemistries. Lithium-ion computer batteries also require that protection circuitry be incorporated into the battery pack to monitor the battery charge and to provide safe voltage and current levels, as well as ensuring that the temperature of the battery remains in a safe operating range.

Cylindrical lithium-ion battery cells are generally tubular in shape, much like the shape of standard alkaline batteries. Several cells are enclosed in a plastic housing and the individual cells are connected in a manner to provide the proper output voltage and to maximize storage capacity (rated in milliamp-hours). Prismatic shaped lithium-ion cells are also available, but they are much smaller and are typically used in devices such as cell phones where weight and space is a prime consideration.

There are several things that affect the life of a lithium-ion laptop battery. Battery degradation is hastened by heat, so storing the battery in a cool environment will prolong its life. Manufacturers typically recommend a storage temperature of approximately 60°F for the long-term storage of lithium-ion batteries. These batteries, as stated previously, do not retain a memory from partial discharge cycles, so full discharge cycles are not required. In fact, partial cycling of the battery will help extend its life. Lithium-ion batteries do have a limited lifetime like the older battery technologies, but this is relatively independent of their charging cycles and is chiefly related to their age. A typical battery will last only 2 to 3 years. This is true even if the battery remains unused so it is important not to purchase a replacement laptop battery until it is ready to be put into service.

The author has established a website for replacement laptop batteries that provides tips and buying advice regarding cheap laptop batteries. An in-depth article on laptop battery ratings discusses the voltage and milliamp-hours specifications that are two of the chief considerations in the choice of a replacement laptop battery.

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