UltraBattery Combines Battery and Supercapacitor Power
By Bill Siuru
Supercapacitors, or ultracapacitors as they also called, are great for rapidly storing large amounts of electrical energy such as during times of regenerative braking in a hybrid electric vehicle. Once charged, they can deliver large bursts of electric power for acceleration. In contrast, batteries are great for long term storage of electric power, but their lifetimes are decreased substantially when they are rapidly charged and discharged, which is the case in a hybrid vehicle with regenerative braking.
CSIRO (Commonwealth Scientific and Industrial Research Organisation) in Australia has developed the UltraBattery to overcome this, combining asymmetric capacitor technology with a conventional lead acid battery in a single unit. Compared to a traditional symmetric supercapacitor with two identical polarized electrodes, an asymmetric energy device has one polarized and one non-polarized electrode. In the CSIRO design, the positive plate is basically split into two parts to serve both battery and capacitor functions.
While combining capacitors and batteries together is not new, the UltraBattery does it without control electronics. The complexity of control electronics adds significant cost as well as space and weight penalties. Rather than control electronics to manage electrical energy in and out of the dual capacitor/battery system, in the UltraBattery energy flows are determined at a chemical level by the internal construction of the unit.
According to CSIRO, the UltraBattery costs about 70 percent less than the batteries currently used in gasoline-electric hybrid vehicles. Also compared to conventional battery systems, the UltraBattery’s lifecycle is at least four times longer and it’s said to produce 50 percent more power. Because the UltraBattery can provide and absorb charge rapidly during vehicle acceleration and braking, it is well suited for hybrids including plug-in variants.
In testing that lasted over 12 months at the Millbrook Proving Ground in the UK, an UltraBattery installed in a Honda Insight hybrid successfully covered 100,000 miles. The UltraBattery was built by the Furukawa Battery Company of Japan and testing was done through the American-based Advanced Lead-Acid Battery Consortium. In this application, there was a 2.8 percent fuel consumption penalty. But at one quarter of the cost, they can reduce the cost of a hybrid by about $2,000.
Besides their use in hybrids, UltraBattery technology could also be used for storing energy from solar and wind sources. In fact, this very application is now being developed by Smart Storage Pty Ltd., a joint venture between CSIRO and Cleantech Ventures.
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