This invention is a system and a method that uses the braking resistor, commonly used and available in electrically or hybrid-electrically propelled vehicles, to limit the precharge current during the startup of a high power ultracapacitor pack energy storage device and/or safely and rapidly discharge an ultracapacitor pack for maintenance work or storage to lengthen the life of the individual ultracapacitor cells and, correspondingly, the whole pack. The use of the braking resistor for precharging an ultracapacitor energy storage pack is an effective and less expensive method compared to other methods such as a separate DC-to-DC converter. This method includes the control logic sequence to activate and deactivate switching devices that perform the connections for the charging and discharging current paths.