webmaster Posted August 20, 2006 Report Share Posted August 20, 2006 Lithium ion batteries ....(sometimes abbreviated Li-Ion) are a type of rechargeable battery commonly used in consumer electronics. They are currently one of the most popular types of battery, with one of the best energy-to-weight ratios, no memory effect and a slow loss of charge when not in use. They can be dangerous if mistreated, however, and unless care is taken they may have a shorter lifespan compared to other battery types. A more advanced lithium-ion battery design is the lithium polymer cell. Advantages Li batteries are lighter than equivalents in other chemistries — often much lighter. This is because lithium ions have an extremely high charge density — the highest of all known naturally occurring ions. Li ions are small and mobile, but more readily stored than hydrogen. Thus a battery based on lithium is smaller than one with hydrogen elements, such as nickel metal hydride, and with fewer volatile gases. The ions need fewer storage intermediaries, so more battery weight is usable as charge, instead of overhead. Li-ion batteries do not suffer from the memory effect. They also have a low self-discharge rate of approximately 5% per month, compared with over 30% per month and 20% per month in nickel metal hydride batteries and nickel cadmium batteries, respectively. According to one manufacturer , Li-Ion cells (and, accordingly, "dumb" Li-Ion batteries) do not have any self-discharge in the usual meaning of this word. What looks like a self-discharge in these batteries is a permanent loss of capacity, described in more detail below. On the other hand, smart Li-Ion batteries do self-discharge, due to the small constant drain of the built-in voltage monitoring circuit. This drain is the most important source of self-discharge in these batteries. Disadvantages A unique drawback of the Li-ion battery is that its life span is dependent upon aging from time of manufacturing (shelf life) regardless of whether it was charged, and not just on the number of charge/discharge cycles. This drawback is not widely publicized. At a 100% charge level, a typical Li-ion laptop battery that is full most of the time at 25 degrees Celsius or 77 degrees Fahrenheit, will irreversibly lose approximately 20% capacity per year. However a battery stored inside a poorly ventilated laptop, may be subject to a prolonged exposure to much higher temperatures than 25 °C, which will significantly shorten its life. The capacity loss begins from the time the battery was manufactured, and occurs even when the battery is unused. Different storage temperatures produce different loss results: 6% loss at 0 °C/32 °F, 20% at 25 °C/77 °F, and 35% at 40 °C/104 °F. When stored at 40% charge level, these figures are reduced to 2%, 4%, 15% at 0, 25 and 40 degrees Celsius respectively. This makes Li-Ion batteries unsuitable for back-up applications compared to lead-acid batteries, and even to Ni-MH batteries @Wikipedia: http://en.wikipedia.org/wiki/Lithium_ion_battery = = Lithium-ion batteries make a grab for power By Vince Biancomano Lithium-ion batteries are poised to do it all. In a two-fold development analogous to DC/DC converters where half-bricks and now quarter-bricks have the capability of some full-bricks, nickel cadmium (NiCd) and nickel metal hydride (NiMH) batteries have become a viable alternative to mains-powered and stand alone DC systems in selected power applications. Now lithium-ions, the battery of choice for powering wireless and portable devices, are making a run at NiCd, NiMH, and the traditional lead-acid battery. Touting new chemistries (the latest of which include nickel cobalt manganese), some of the newest lithium-ion types claim up to 50 percent more power, longer run times, faster charge times, and longer lifetimes than nickel-cadmium. Beyond that, lithium-ions (nominal 3.6-volt devices, versus NiCd’s and NiMH's 1.2 volts) are evolving into so-called "big format" products in hopes of claiming a piece of the lead-acid market. Indeed, while the number of new battery products into the market seemingly has slowed to a comparative trickle the last two years, conquering lead-acid remains a goal of just about every power source, including supercapacitors. The traditional "automobile" battery, however, retains stalwart support among major users and, they say, is likely to remain strong. Several new lead-acid entries bring power to their argument. ...MORE: http://www.powermanagementdesignline.com/news/187900140 = = = ANOTHER CHALLENGE : Battery Life Lead-acid : 4 years Li-ion...... : 7 years New Li-ion: 20 years maybe, by adding other chemicals Link to comment Share on other sites More sharing options...
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