Frequently Asked Questions
HOW WILL ULTRACAPACITORS/ SUPERCAPACITORS/EDLCS HELP MY PRODUCT?
Ultracapacitors have very high specific power which is largely unaffected by temperature through their operational range. When ultracapacitors are paired with high energy sources, the combined system peak power can increase dramatically.
HOW LONG WILL ULTRACAPACITORS LAST?
Ultracapacitors have a design life of 10 years at rated voltage and 25 °C. Reducing voltage and temperature can increase design life, while increasing temperature and voltage will shorten design life. Most applications will use cells at a lower nominal voltage to get longer design life at higher temperatures.
WHAT IS THE OUTPUT VOLTAGE OF AN ULTRACAPACITOR?
An ultracapacitor only provides energy as its voltage decreases and absorbs energy as its voltage increases. The output voltage is dependent on the state of charge. An upper and lower voltage limit has to be used to determine working voltage range.
TO WHAT VOLTAGE CAN THE ULTRACAPACITORS BE CHARGED?
IOXUS Ultracapacitors can be charged from 0.0 VDC up to 2.7 VDC.
HOW MUCH ENERGY WILL AN ULTRACAPACITOR PROVIDE (HOW LONG WILL MY APPLICATION RUN)?
Ultracapacitors store much more energy than other traditional capacitors, but substantially less than batteries. To determine the energy stored in an ideal capacitor take the upper voltage and square that, then subtract the square of the lower voltage and multiply the result by one half the cell capacitance to get the energy transferred in joules. E = 1/2C x (Vupper2 – Vlower2)
HOW MUCH POWER CAN IOXUS ULTRACAPACITORS PROVIDE?
Ultracapacitors are power limited only by their equivalent series resistance (ESR). IOXUS ultracapacitors can be charged or discharged at currents up to 1000C and can provide peak power densities in excess of 20 kW/kg.
HOW DO I CHARGE AN ULTRACAPACITOR?
Ultracapacitors follow strictly current-based charging rules. An ultracapacitor cell will absorb as much current as is supplied to it, while its voltage increase is based on how much charge it has accumulated. Care must be taken in designs for charging ultracapacitors at a low state of charge, since they will act like a short circuit when their voltage is near zero.
WHAT ARE THE RULES FOR CONNECTING CELLS IN SERIES?
Most applications require cells to be connected in series to reach higher working voltages. For cells in series, it is best to derate the cells’ rated voltages to reduce the impact of unbalanced cell voltages on system life. As identical cells are connected in series, ESR increases as a multiple of the number of cells and capacitance decreases by the quotient number of cells. (ESRTotal = ESRCell x # of cells, CTotal = CCell / # of cells)
WHAT ARE THE RULES FOR CONNECTING CELLS IN PARALLEL?
Cells can be connected in parallel if a capacitance is needed that is larger than an available cell size. Cells of different sizes can be connected in parallel, as long as the same types of cells are used for each series connected unit to match capacitance and ESR. For identical cells connected in parallel, ESR decreases by the quotient number of cells and capacitance increases as a multiple of the number of cells. (ESRTotal = ESRCell / # of cells, CTotal = CCell x # of cells)
WHAT IS CELL BALANCING AND DO I NEED IT?
Cell balancing is a way to reduce the voltage spread in cell voltages resulting from an imbalance in leakage currents, an imbalance in capacitance, or an imbalance in power losses from ESR. Cell balancing can range from a simple 1 percent tolerance resistor across the terminals of each cell, which is sized to dissipate 10 times the nominal cell leakage current to complex circuits which shuttle charge between cells. In general, it is a good idea to have cell balancing for applications requiring long cell life.
CAN I REPLACE BATTERY XYZ WITH ULTRACAPACITORS?
Usually no, but there are certain low-energy applications such as short-term ride through for generator starting, engine starting, and motor starting that can be powered by ultracapacitors without a battery. The use of high-efficiency DC-DC converters can greatly extend the working voltage range for increased energy extraction from cells while providing a regulated output.
DOES IOXUS HAVE ANY PREPACKAGED ARRAYS OF CELLS OR MODULES?
Yes, IOXUS has several modules available. You can see some of these modules online at our Modules page. Other modules may be available, but not on the website. If you have a specific module requirement, please contact our sales department by writing to firstname.lastname@example.org
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