Supercaps in automotive applications (e.g. smart car key)

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.

Supercap test results

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


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Why are components like ultracaps called different names?

The variety of terms is explained by the English-language terms commonly used in the electronics industry, which are often mixed with German terms or used synonymously. In some cases, manufacturers have also introduced artificial terms to better distinguish themselves from competitors. Here are the most important examples:

Double layer capacitors (DSK) are referred to synonymously as:

  • EDLC (Electric Double Layer Capacitor)
  • Supercapacitors = Supercaps
  • Ultracapacitors = Ultracaps
  • Goldcap™ [Panasonic]
  • Boostcap™  [Maxwell]
  • Greencap™  [Samwha]
  • PURIXEL™  [Pureechem] for supercap cells
  • PURETRON™  [Pureechem] for supercap modules

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