Search This Site For  

powered by FreeFind

Miscellaneous/Ask Isidor 051212
 (February 2007) No Ultracaps In Electric Cars Yet, But Maybe There Should Be
from Electronic Design, Feb 15 2007, p. 24

After noting the Chevy Volt, a GM concept car using Lithium-ion batteries, author Tuite cites comments by Maxwell Technologies VP John Miller which suggests that the hybrid can be structured to include Ultracaps (electrochemical capacitors). Supporting the idea is that the cycle life of batteries may be an important factor to consider because of the many partial charge/discharge cycles encountered in driving.  Adding Ultracaps to absorb the dynamic cycling and leaving the batteries for deep energy discharges may extend the energy storage portion of the hybrid to 15 years. (Ed. Note: With road experience for a decade coming in for the Toyota RAV4 with Nickel-metal hydride batteries, the 100,000 mile barrier appears to be a virtual wall which has been broken. Because Lithium-ion can add a degree of size reduction, and therefore potentially offer greater range for a given size, the question arises as to the need for greater life than that offered by Lithium-ion batteries. Note that the last two versions of the Honda FCX, fuel cell powered auto have used supercaps instead of batteries.)

 (December 2005)                        Selecting an Ultracapacitor

Price reductions of two orders of magnitude in the last 10 years have changed the designer’s choices in dynamic power control. This story identifies The important characteristics of electrochemical double layer capacitors which make them complementary with battery or fuel cell systems, or as stand alone power sources. High rate of charge acceptance, discharge and cyclability all are good characteristics. Utilization in series and parallel opens challenges of discharge characteristics and  cell balancing. Often overlooked is the low impedance of the cell which must be taken into consideration when charging.
Electronic Products, November 2005, pp. 29-32
 (Oct. 2003) Gold is studied as a replacement for carbon in ultracapacitors.  Professor Michael Cortie of the University of Technology, Sydney and Dr. Elma van der Lingen from Mintek in Jahannesburg are finding that the ‘gold’ ultra-capacitors did not over heat and could store up to six times the energy of standard capacitors.  Gold does not suffer from the high internal resistance that limits carbon-based ultracapacitors.  

In working with their prototype, the researches used an intermetallic compound of gold and aluminum called purple glory.  The aluminum is them chemically removed, thus leaving a sponge of pure porous gold.  Because of the holes (pores), there is a very large surface area which is utilized  for the rapid exchange of electrical charge.
Shield Ultracapacitor Strings From Overvoltage Yet
Maintain Efficiency
An ultracapacitor connected in series for greater terminal Voltage can suffer damage during charge due to individual cell overvoltage. This story describes the advantages and disadvantages of passive and active Voltage equalization methods to protect each cell in the string.(07-2BD76-13)
May 27, 2002, pp.81-85
T/J Technologies receives $2 million award from U.S. Dept. of Commerce to develop hybrid ultracapcitor/fuel cell power packs for portable electronics. The Company promises to alleviate two key frustrations for users of rechargeable batteries: limited run-time and access to a wall or vehicle outlet for recharging. The hybrid power packs are expected to deliver five times longer run time and be instantly “rechargeable” simply by refueling. (12-01 BD69-12)
(02-01-02 BD70-9) Ness Capacitor Co. introduces 2.7 Volt ultracapacitors. The company says it is the first ultracapacitor family with continuous operating Voltage rating higher than 2.5 Volts. The NESS 2.7 V ultracapacitor is said to have the highest capacitance and energy storage densities and the lowest Equivalent Series Resistance of any commercially available components of comparable size and weight. The key to performance is attributed to its porous carbon electrodes. Some targeted markets are for EVs’ and hybrid EVs’ acceleration and braking, industrial actuation and control, wind and fuel cell power conversion, and UPS switchover bridging.