FCX 2002.12.2

More powerful drive assistance, more efficient energy recovery during braking
Honda has independently developed a new high-performance ultra-capacitor (electrical two-layered condenser) to serve as a supplementary power source to the FCX's main power sourcethe fuel cell stackfor more powerful performance under various driving conditions. The new ultra-capacitor combines the electrical storage capacity needed for high output and high responsiveness with solid reliability. It stores the energy produced during deceleration and braking and provides powerful drive assist during startup, acceleration and at other times when an extra boost is required. The ultra-capacitor's internal resistance is lower than that of a battery, and moreover, because it stores and discharges electricity in response to voltage fluctuations in the fuel cell stack, it doesn't require a converter for voltage regulation as in a battery system, so it delivers higher output. The result is improved drive-power performance and higher system efficiency.
In order to improve electrical storage capacity, a new high-performance activated-carbon electrode was used, and electrode wrapped-element construction employed to achieve high-density electrode packing right out to the case. This results in energy efficiency 7-10% higher than that of a nickel-hydride battery, the difference increasing with output. The capacitor achieves an energy density of 3.9Wh/kg (at a 2.7-1.35V discharge) and an output density of over 1,500W/kg. Its charging and discharge functionality is among the highest in the world for a capacitor.
(Values based on Honda in-house testing)
A combined fuel cell stack and ultra-capacitor deliver powerful,
responsive performance and outstanding fuel efficiency
The fuel stack acts as the main electrical power source, aided by the powerful assist function of the ultra-capacitor during startup, acceleration, and other times when a large boost is required. In the low to mid speed ranges, the FCX delivers powerful, torquey acceleration that can surpass that of a gasoline-powered vehicle. During deceleration, energy is recovered and stored in the ultra-capacitor. Electricity from the fuel cell stack is also stored there at this stage. And during idling, an auto idle stop system cuts the power to the motor to reduce fuel consumption. Energy management is optimized in the PCU (Power Control Unit) for efficient power use and waste-free recovery. As a result, the FCX achieves an energy efficiency of 45%twice that of a gasoline-powered vehicle and 1.5 times that of a hybrid car. The FCX also attains fuel economy greater than that of a hybrid vehicle; another area in which it displays superb practical driving performance.
(Values based on Honda in-house testing)
Fuel cell stack + ultra-capacitor output characteristics
Comparison of drive power energy efficiency* Comparison of fuel economy*
The drive motor responds instantaneously to the driver's operation of the accelerator, displaying the combined powerful output of the fuel cell stack and ultra-capacitor to make startup and acceleration nimble and torquey compared to gasoline-powered cars, hybrids, and electric vehicles. The result is offthe-line performance comparable to that of a high-performance midsized gasoline-powered vehicle.
Startup and acceleration g's Off-the-line performance: distance
traveled 3 seconds after startup
*Comparison with Honda vehicles


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