Applications
Supercaps in the automotive industries
Applications | Rainer Hake | reading time: 6 minutes
The car: smart applications become a competitive advantage
Competitive advantages in the automotive market are increasingly created by so-called "smart applications". In essence, these are networked, highly complex ICT applications that offer the customer either more comfort and/or safety. The energy required for this must be supplied by ever-smaller supercondensers. These are required to deliver ever higher pulsepower with a practically unlimited lifespan. Supercap manufacturers such as CAP-XX have specialised in such demanding requirements.
Supercapacitors reduce the load on primary batteries
There are numerous application scenarios for supercaps [alternatively: ultracaps, ultracapacitors]. Be it the car key, the sound system, the door lock, the window lifter, seat and steering wheel adjustment and other electro-mechanical modules. All of them require high electrical power, especially in the starting phase. However, the cablecross-sections required for this cannot be increased, if only for economic reasons. In the phases of highest energy demand, supercondensers prove to be the perfect support for the primary batteries. Ultracondensers have proven their worth in voltage stabilisation for some time now. When starting the engine in stop-start mode, the ultracap can maintain the voltage and prevent undervoltage of the vehicle's electronics, such as EMS, GPS, radio, etc.
Supercaps in smart car keys
Car manufacturers have extended the functionality of their remote smart keys by integrating various features, such as encrypted security codes, remote control of the air conditioning system or an intelligent call function. However, due to the larger radio range required, these functions require much more energy compared to the simple lock and unlock function of older car keys. The conventional button cell batteries commonly used for car keys cannot sufficiently meet this increased energy demand. As a result, car owners would have to replace batteries more often. Alternatively, the design of the key fobs could be adapted to larger batteries. Both options are undesirable for reasons of usability and cost.
The simplest and most effective solution is the integration of CAP-XX supercaps. These have a low equivalent series resistance (ESR) and an ultrathin prismic design (variants DMF low ESR high power, DMT long life high temp or DMH ultra-thin). The solution to the problem is the simple integration of the supercap into the housing of the key fob. The energy spikes are intercepted by the supercapacitor, forcing the primary battery not to go to the power limit. The result: a significant increase in battery life.
The figure below shows an accelerated test with two CR2032 batteries with and without a HA202 supercapacitor, 120mF, 120mΩ supercapacitor, running a short ranged (Blue Tooth Low Energy = BLE) BLE TX module. A single BLE TX draws~15mA for around 50ms, similar to a smart key’s RF TX power. The test in Fig1 transmits once per second until module brown-out. A typical new CR2032 battery has an internal resistance ~10Ω. As the battery is discharged, the internal resistance will increase beyond 60Ω. Drawing15mA will drop the battery voltage to ~2V, causing the electronics to brown out, while a CR2032 battery supported with an HA202 would still be ~2.8V. This reduced voltage drop allows the BLE TX to utilize much more of the energy in the battery before brown-out, hence the 55% increase in battery life observed.
Supercaps help reduce weight
A modern car contains no less than 1 mile of wiring. These copper cables provide power, enable control and collect information throughout the vehicle. With an increasing focus on improving fuel efficiency, car manufacturers are concentrating on reducing weight without restricting functions. The low equivalent series resistance (ESR) and high capacitance (C) of a supercap compensate for the effects of cable impedance on the supply voltage. This allows a thinner wire to be used, which reduces the weight of the electrical cables.
Smaller cable diameters in audio systems, all without interference
One system that can benefit greatly from this is the audio system. The high-quality loudspeakers responsible for the impressive sound often have a power rating of over 200W. To meet such a high power demand, car manufacturers have to use much thicker power cables to eliminate harmonic interference due to voltage fluctuations in the supply rail due to cable impedance.
The extremely low ESR and good frequency response of the CAP-XX supercapacitors ensure that the audio device's supply rail remains stable, allowing thinner cables to be used. This saves considerable weight while providing unparalleled audio quality.
Electromechanics with high starting currents - supercaps help
Various electro-mechanical modules responsible for door locks, window lifters, electric seat and steering wheel adjustment require only high power to overcome inertia and provide the motor's starting current. Subsequently, only a lower power is required until the action is completed. Such modules can benefit from an integrated supercapacitor: This covers the peak load - the thinner coating is then completely sufficient for the average power after the startup peaks.
Another example is the indicator with a duty cycle of 50%. A supercap supplies the peak flasher current, while the compressor is dimensioned for the average current.
Supercaps are the emergency power supply in the car
Modern vehicles are designed to have several systems to protect the occupants. All these safety systems depend on the electrical system. Any failure of the electrical system can mean a catastrophic event. Supercapacitors can help to reduce this risk. A supercap is not only capable of delivering high pulse power, but also stores a considerable amount of energy. This is then ready to power important vehicle systems for a short period of time so that a safe stop is possible in the event of an electrical system failure. With a virtually unlimited cycle time, a supercap is a very reliable source of reserve energy.
Courtesy of CAP-XX Ltd, Australia. Translation and editorial adaptation: Rainer Hake