The high power and long cycle life merits of ultracapacitors are clear. Yet high volume ultracapacitor applications have not materialized. One drawback of ultracapacitors is the wide operating voltage. During usage, the voltage of an ultracapacitor will swing from about 2.5 volts to near 0 volts per cell. This is undesirable because most electronic systems require a stable input voltage. Another technical obstacle is over-charge protection. Not only will the working life suffer as an ultracapacitor cell is overcharged, but the safety of the system may be compromised. Thus, active cell balancing is needed, which complicates the system control and adds cost. By integrating power electronics and battery management, AeroVironment has designed an ultracapacitor pack. The "AV Energy Pack" provides stable voltage output while protecting the ultracapacitors from overcharge. The system is compact and uses mass-produced components to minimize the cost impact of the electronics. The "AV Energy" pack can enable ultracapacitors to be used in many emerging applications.
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