Friday, July 22, 2005

Battery Technology – Even Nuclear Options are in the Game

Many applications in the world of virtual instrumentation require battery power. The limitations of current battery technology require manual processes (e.g. replacing batteries) and provide limited solutions -- the battery lasts only so long. Emerging technologies in batteries hold some promise. Even nuclear options are under research. Direct Energy Cell (DEC) conversion generates power from the decay of a radio element source. It uses a single step capture-and-conversion technique rather than an electrochemical process. Tritium is one example which has a half life of over 12 years. It would work well for wireless sensor networks in hard to reach locations since you wouldn’t have to change the battery but once a decade if even that. While it’s not a good fit for mass market consumer devices due to cost and obvious safety issues, it would fit well for industrial applications which have more stringent requirements such as decade-long lifetimes.

Microcombusion technology generates heat by burning small amounts of liquid hydrocarbons. The heat is then converted to electricity by other means. This technique packs a lot of energy into a very small package.

Other advances include polymer batteries which use a different type of electrolyte. This allows for ion exchange but does not conduct electricity. Most batteries using this technology actually form a hybrid between the old gel-based electrolyte and the new one that contains no gel. The polymer base allows for molding the battery into unique shapes and forms which is useful for portable applications which may not accommodate fixed shape batteries.

Another vector for battery innovation is packaging. Power Paper makes batteries from a flexible material made of polymer that is embedded with a propriety ink using a mass-printing technology. It produces a 1.5V battery that can be used in many materials such as band-aids, paper, plastic and other materials and can form any shape.

Smart batteries come with additional circuitry that indicates the state of charge and the state of health of the battery. This is useful for the user who needs to know the condition of the battery. There’s a simple one-wire version that brings the data out to a chip for measurement, and there’s also a more sophisticated SMbus version which provides a data communication bus complete with protocol standards set by Intel and Duracell back in the early 90s. This allows the battery to take charge control over from the charger and lets the battery determine how it will be recharged.

The first generation of advanced power supplies, such as lithium-ion batteries, will soon be replaced by fuel cells which do not require replacement or recharging and have high output densities. Size is also an important factor to consider, as more advanced equipment requires the use of more components and limitations on real estate (i.e. size of the entire finished product). There are numerous examples. From MTI comes a Micro Fuel Cell technology using DMFC which is a Direct Methanol technique. It’s not yet a shipping product, but appears to be in prototype stage. Manhattan Scientifics also makes a methanol-based Micro Fuel Cell. Their technology can produce 3 times the power of Lithium battery with the goal of achieving a 20x improvement.

Super capacitors store energy as a static charge rather than an electrochemical process. They are a cross between traditional capacitors and batteries. Current capacitors have a limited capability to store energy, like existing lithium ion batteries, and have very limited capacities to deliver that energy quickly and efficiently. Applications such as starting a car require a surge of electricity. Supercapacitors combine battery-like energy storage with capacitor-like power discharge, and can be used either standalone or in conjunction with a battery. Nanotechnology, in particular carbon nanotubes, offers improved materials for supercapacitors.

If you are seeking a battery solution for your virtual instrumentation application, here’s an article discussing the basics.

If you are working with battery technology, I would like to hear from you. Please email me at hall.martin@ni.com.
Best regards,
Hall T. Martin

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