Lithium-ion batteries make a grab for power

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.

Lithium takes the lead
The U-Charge RT and U-Charge XP power systems from Valence Technology (Austin, Tex.), for instance, include eight large-format lithium-ion battery modules. Valence says the 12-volt storage systems, which are provided in industry standard lead-acid form factors, offer twice the run-time and a significantly lower total cost of ownership than lead-acid. Valence also says they’re one-third lighter.

The U-Charge RT products, in four models, provide up to 30 amps continuous and have a capacity of 24 to 134 A-h. The U-Charge XP, also in four models, provide from 500 to 1,700 watts continuous. The batteries use the company’s Saphion Technology, which is designed to be more chemically stable and safer than traditional oxide-based batteries.

Again offering an alternative to lead-acid batteries, this time for telecom applications, the Intensium 3 from Saft (Baltimore, Maryland) is a 48-volt lithium-ion battery system suited for 19-inch, 3U rack-mounted applications. This scaleable system allows user to connect up to eight units in parallel to provide 18 kW-h of backup. Meeting the requirements for extended lifetime as needed in telecom systems, Intensium 3 has a projected 10-year lifespan at +40°C, and a 20-year life at +20°C.

Power on the platform
Lithium-ions are also digging in deeper for industrial tasks. Valence’s IFR18650p released last year is a 3.2-volt, 1100 mA-h source that’s intended to compete with NiMH and NiCd batteries and was promoted as the only safe large-format lithium-ion rechargeable. Advancing over Sony’s Nexelion brand, said to be the first hybrid lithium-ion rechargeable, and Toshiba’s 600 mA-h lithium-ion battery introduced last year that the company promoted as a breakthrough in its ability to recharge to 80 percent of capacity in an hour (60 times faster than typical), the Valence battery can charge to 95 percent of capacity in 30 minutes. Despite these advances, with larger systems one looming issue for lithium-ions will likely be on securing faster charge times without adversely affecting overall battery lifetimes.

Other new arrivals include a lithium-ion battery using phosphate-based chemistry from A123 Systems (Watertown, Mass.) focused on securing the highest peak powers (a claimed 3 kW, in this case). The company’s first offering, customized for Black & Decker’s DeWalt line of 36-volt power tool platforms, touts a five fold power gain and 10 times longer life over traditional high-power battery technology, and a 5-minute charge time (see www.a123systems.com).

At the lower-power end of the spectrum, new tools for traditional lithium-ion batteries continue to add value. A development kit from Atmel (San Jose, Calif.) for instance, the ATAVRSB100, allow developers to simulate critical lithium-ion battery situations for their laptop, medical equipment, and portable instrumentation applications. The board comprises three support modules to simulate individual cell voltage, total cell stack voltage, and charge/discharge current.

Long life to lead-acid
With all the advances, the death of lead-acid has been greatly exaggerated; the tried and true lead-acid battery continues to improve. The GC family of valve-regulated, lead-acid (VRLA) batteries from GC Electronics (Rockford, Ill.), for example, comprises 75 models rated at 1.2 to 230 A-h for 4-, 6-, 12-, and 24-volt applications. They include high-power options on select models that claim 15 percent more capacity than their standard counterparts.

The 6-volt, 12 A-h gel batteries from EHM (Las Vegas, Nev.) use a design having grids made from a lead-calcium alloy that enables a battery float life of 15 to 20 years. The company touts a unique low-cost gas recombination system that extends the batteries to very long-life applications, including emergency lighting and traffic monitoring.