KEMET has introduced a supercapacitor balancing development kit for its S301 family of 60mm diameter capacitors.
Used in series, supercapacitors need electronics to ensure no capacitor goes over the rated voltage as the string approaches full charge – 2.7V in this case, see below.
The kit includes two-stage active balancing circuits to ensure that voltage across each supercapacitor is approximately equal. There are enough balancing PCBs, bus bars, screws, washers and wires to assemble six 60mm diameter capacitors – capacitors not included.
“Typical applications include product validation, prototyping, low volume production and custom configurations,” said the firm.
Kemet supercapacitor balancerActive balancing?
Active balancing means two different things in the worlds of batteries and supercapacitors.
Balancing in both worlds describes keeping terminal voltages in check when charging series strings – it also sometimes applies to discharging.
Passive balancing with batteries – in particular Li-ion batteries as they are very touchy about cell voltage – involves an electronic shunt voltage regulator across each cell dissipating excess charging energy when the cell terminal voltage reaches maximum.
Active balancing for Li-ion batteries involves some way of passing this otherwise wasted energy to cells along the string that are not yet up to voltage – usually by inductive switching.
Passive balancing for supercapacitors is putting an equal resistor across each one in a string, forming a dissipative potential divider – which involves an uncomfortable trade-off between dissipation and balancing ability unless only slow charging is expected.
Active supercapacitor balancing tends to mean something similar to passive balancing in batteries – either shunt regulators that clamp the maximum voltage across each individual cell in the string, or some form of active potential divider that keeps the terminal voltage equal on a pair of supercaps connected in series.
source: http://www.electronicsweekly.com/news/products/power-supplies/supercapacitor-balancing-kit-2014-07/
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