Ultracapacitor-based energy storage systems typically comprise an ultracapacitor stack with an interfacing DC/DC converter. This paper analyses two different topologies of three-level bidirectional DC/DC used for interfacing the ultracapacitor stack. The impact of the voltage rating of the ultracapacitors on the performance of three-level bidirectional DC/DC converters is studied in detail. In particular, we show that the wrong choice of voltage rating could potentially cause an unequal sharing of energy among the filter capacitors in the DC-link and discontinuous load currents during the charging and discharging phases of the ultracapacitor, respectively. The analysis reported in this paper is supported using experimental results on a 24 V laboratory setup comprising of 10 series-connected ultracapacitors. © 2022 IEEE.