The future of transportation is inevitably all-electric, and its driving forces are electric energy storage devices. This is particularly true for urban mass transit modes, such as trains, trams, buses, and public utility trucks. Ultracapacitors (UCs) are gaining popularity in transportation storage applications to supply peak power and power transient demands, especially in mass transit electrification. The inherent low open circuit voltage is overcome by connecting UCs in series to obtain the desired DC-bus voltage. However, variations in internal parameters of these devices can lead to unbalanced voltages across each UC cell during charge-discharge cycles, which negatively affects lifetime, energy storage efficiency, and safety of the UC bank. To overcome this issue, a suitable cell balancing (power management) circuitry is employed, which enhances the lifetime and performance of the overall UC bank. This paper reviews the concepts of various UC cell balancing methods and the associated power electronic converter modules. Comparison between the various techniques are presented and different balancing methods are grouped based on their principle of operation.