Can Supercapacitors replace batteries?
I have been looking at the new Kemet Supercapcitor Series to see if they can be used to replace batteries.
It would be best to first define the difference: Electrochemical double layer capacitors, also known as supercapacitors or ultracapacitors, are energy storage elements with high energy density compared to conventional capacitors and high power density compared to batteries. Unlike conventional capacitors, where no chemical reactions is used and small amount of energy is stored by physically storing electric charges between two conductive plates upon application of an electric field, these electrochemical storage devices cross the boundary into battery technology by using special electrodes and electrolyte, and have capacitance values as high as 3500 Farads in a single standard case size with long cycle life (>100 000 cycles).
Supercapacitors are the preferred choice in applications requiring a large amount of energy to be stored and delivered in bursts repeatedly. Batteries have high internal resistances (ESR) that are too large to continue to consistently deliver high-power pulses without increasing the risk of performance failures. Supercapacitors ultra-rapid charging and delivery of high current make them an ideal candidate to balance loads on power grids, standby/backup power supplies, or peak-load enhancer for hybrid vehicles. In these applications, supercapacitors will supply power to the system when there are surges or energy bursts, while the batteries can supply the bulk energy since they can store and deliver larger amount energy over a longer slower period of time.
The Kemet Supercapcitor Series have characteristics ranging from the traditional capacitors and batteries. As a result, supercapacitors can be used like a secondary battery when applied to in a DC circuit. These devices are best suited to low voltage DC hold-up applications such as embedded microprocessor systems flash memory.
• Wide range of temperature from -25C to +85C
• Maintenance free
• Maximum operating voltage:5.5 VDC
• Highly reliable against liquid leakage
• Lead-free and RoHS Compliant
• Real time clock back up
• Embedded RAM and flash hold-up
• Motor drivers, servo motors, high power LED’s, buzzers
In conclusion Supercapacitors offer a promising alternative approach to meeting the increasing power demands of energy storage systems and electronic devices. With their high power density, ability to perform in extreme temperatures, and millions of charge-recharge cycle capabilities, supercapacitors can increase circuit performance and prolong the life of batteries. This can add value to the end-product and ultimately reduce the costs to the customer by reducing the amount of batteries needed and the frequency of the replacement of the batteries, which adds greatly to the environmental friendliness of the end-product as well.
If you would like to find out more information or purchase any of the Kemet Supercapcitor series (FG, FC, FR, FY, FS & FT) click on the link below
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If you have the room, Supercapacitors would make an excellent battery replacement in certain circumstances. Different rechargeable batteries have different characteristics that make them better in some areas and not others. Lets list a few plus and minus's and include supercapacitors.
LiOn: needs very controlled charging for safety, self discharge > 18 months, High energy per volume and weight, medium available maximum current drain. No memory effect, Roughly 500 charge cycles
NiMh: Charging not critical, Medium energy to volume/weight , Very high max current drain. Self discharge 6months to a year. Less memory effect, Roughly 500 charge cycles.
NiCd: charging not critical, medium to low energy to volume/weight, Very high max current drain, Self discharge 6 months to a year. Memory effects. Roughly 500 charge cycles.
Supercapacitor: Charging not critical, low energy to volume/weight. Self discharge 6 months. max current drain depends on design. Number of charge cycles, >50,000.
Supercapacitors currently seem like a perfect fit for solar charged devices since they don't waste much energy when charging, and can be recharged many many more times than chemistry based rechargeable batteries. They are merely 10 or more times larger for an equivalent battery watt hours stored. An air tight unit is feasible since they won't vent gases unless damaged, unlike NiMh and NiCd which seem designed to vent caustic gases right against the battery holder.
Supercaps would be great in devices that never need to be opened. Currently, their size per watt hour means they won't be used in phones or tablets currently. There will need to be a radical improvement to the manufacturing process before that becomes possible.
But if your device has the room, and you need it so you never need to open the case ever, then I'd go cap.