A system for balancing ultracapacitors, the system comprising:
- a plurality of switching devices comprising a first pair of the switching devices including a first switching device and a second switching device and a second pair of the switching devices including a third switching device and a fourth switching device,
- a balancing circuit comprising a single balancing capacitor, wherein the balancing circuit is directly connected to the first pair of the switching devices and the second pair of switching devices;
- a control circuit communicatively coupled to each of the plurality of switching devices, the control circuit configured to:
- control operation of the first pair of the switching devices to couple the balancing capacitor across a first ultracapacitor of a plurality of ultracapacitors to transfer an electrical charge from the first ultracapacitor to the balancing capacitor, the electrical charge being an amount needed to make a voltage across the first ultracapacitor and a voltage across a second ultracapacitor be within 10%;
- control operation of the second pair of the switching devices that is different than the first pair to couple the balancing capacitor across the second ultracapacitor of the plurality of ultracapacitors to transfer at least a portion of the electrical charge from the balancing capacitor to the second ultracapacitor, the electrical charge being an amount needed to make the voltage across the first ultracapacitor and the voltage across the second ultracapacitor be within 10%;
- control operation of the first pair of the switching devices to decouple the balancing capacitor from the first ultracapacitor subsequent to the electrical charge being transferred from the first ultracapacitor to the balancing capacitor, and
- control operation of the second pair of the switching devices to decouple the balancing capacitor from the second ultracapacitor subsequent to the at least a portion of the electrical charge being transferred from the balancing capacitor to the second ultracapacitor, wherein the first ultracapacitor has an electrical charge greater than the second ultracapacitor prior to the at least a portion of the electrical charge being transferred from the balancing capacitor to the second ultracapacitor, and
- wherein the balancing capacitor comprises an ultracapacitor that is separate from the plurality of ultracapacitors and has a capacitance that is smaller than a capacitance of each of the plurality of ultracapacitors.