No extra balancing between the units other than 5 W, 100 kOhm resistors in parallel to each unit is required. Thermal performance is excellent. NASA maintained the capacitors' temperature between 22 - 250 C without extra hardware.

The original bank of 30 capacitors can be now replaced by 18 new units with the total weight of 650 kg, which compared to the original weight of 960 kg it is an improvement of 30%. This can be further improved with the use of Aluminum, in place of steel, for the housings.

IMPORTANCE OF EFFICIENCY AND DURABILITY
The two most important performance parameters of the HEV capacitors are the charge/discharge efficiency and durability. Since the capacitor is not the primary source of power for vehicular propulsion in the hybrid electric vehicle, it must accept and deliver energy with minimal losses. To be economically viable the capacitor must be durable and last the life of the vehicle. NASA found that the battery life in their hybrid electric bus was considerably less than a year.

With the round trip efficiency of 97% and RC product 0.35 seconds, the super capacitor will provide unmatched performance. RC time constants indicate capacitors power performance. The faster the capacitor works the less energy will be dynamically dissipated. The maximum possible energy to be stored in the capacitor is 50% whereas the other half is dissipated as heat. A capacitor with a RC equaling 5 seconds must be 1.8 times larger than the capacitor with a RC equaling 1 sec. When a RC=0.3 sec this relationship is even more pronounced. This is why the optimum HEV capacitor may not necessarily be the one offering the highest energy density, since power performance strongly influences system efficiency.[10] The super-capacitors can cycle through hundreds of thousands of charges-&-discharges without performance degradation. The sealed steel canister provides excellent protection from the environment. No gas escaping from the capacitor during its operation signifies low static losses or leakage current. The static dissipation is highly undesirable since it indicates irreversible chemical reactions. Such reactions can seriously reduce the capacitor's operational life through corrosion, electrolyte consumption and /or internal generation of gas.[10] At a fraction of the cost of competing technology, Properly operated, Tavrima capacitors will last as long as the vehicle itself.

TECHNOLOGY
The Tavrima super-capacitors can be characterized as an "application specific" technology driven by specific target requirements. Tavrima products have proven to be flexible, fast and low cost. The technology is protected by US patents: 5,557,497 and 5,420,747.

There are two basic super-capacitor technologies available: pseudo-capacitance and double-layer-capacitance. The latter technology comprised of carbon electrodes and organic electrolyte, to provide maximum possible energy density, is the most prevalent. Some manufacturers prefer aqueous electrolyte to organic, due to the much higher specific power and efficiency. Each approach has its pros and cons and, perhaps, none can be identified as the best technology without first defining its application requirements. The demand depends upon the application and the viability of the products in accordance with the market mechanisms. The super-capacitor incorporates a patented carbon electrode with an aqueous electrolyte technology to achieve extremely high power and energy densities combined with proven performance and durability.

PRODUCTS
Tavrima super-capacitors have been developed to meet the specific application generally described as internal combustion engine starting. The benefit of this application is twofold: The battery life and starter cranking force is doubled. When the super-capacitor works in tandem with the battery its specific energy is less important than its specific power and cost. Hence the choice of the aqueous electrolyte is well justified for this application. The technology was developed in the USSR 14 years ago as an efficient low cost source of pulse power. This super-capacitor has been used in numerous successful applications predicated on weaknesses of starter batteries. Its powerful discharge has easily starts 3500 hp diesel locomotive engines in Siberia. It has also provided the power for the transient load leveling of Moscow's subway cars.

High voltage and power, proven durability and low cost, make the Tavrima products highly competitive compared to the much more expensive, energy dense, but less efficient and less powerful organic super-capacitors. Many HEV engineers worldwide recognize the pronounced qualities of the Tavrima super-capacitors. With their ability to meet peak power demands, Tavrima super-capacitors allow the optimization of overall energy requirements. The transient power characteristic of the HEV increases the size, complexity and cost of the battery. Even though the peak power demands on the battery may occur during less than 10% of the application's operation, the battery must be sized for peak power, rather than the average power discharge. Accepting the charge at the same rate as the discharge the capacitor is an ideal storage for capturing the regenerative energy of braking. The capacitors can be stored completely discharged, are maintenance free and operate effectively in hot, cold and moist environments. The Tavrima's super-capacitors are the most powerful, reliable and least expensive pulse power capacitors on the market today.

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