Ultracapacitors can be quickly charged and discharged, and can stand up to an unlimited number of cycles.
"The trick is to turn some bus stops along the route into charge stations, says Dan Ye, executive director of Sinautec [MAKER OF THE CHINESE BUSES]. Unlike a conventional trolley bus that has to continually touch an overhead power line, Sinautec's ultracapacitor buses take big sips of electricity every two or three miles at designated charging stations, which double as bus stops. When at these stations, a collector on the top of the bus rises a few feet and touches an overhead charging line. Within a couple of minutes, the ultracapacitor banks stored under the bus seats are fully charged. [...]"