The battery system used in the PRC series is standard alkaline batteries.  The batteries will operate the timer for approximately 55 hours of clock running time (100 hours for the PRC5-6), which is the entire season in most cases.  A replacement set of batteries for the next season costs about $6 for the -4 models (or $16 for the -6 model for 100 hours of operation!).  

Contrast this with any other system that uses rechargeable batteries that must be charged before every use.  Invariably, someone will forget to plug the unit in and it will die in the middle of an event.

One design goal of the PRC series was to have a battery system that required no attention for the entire season.  You just take it to the event and use it--no fooling around with "plugging it in".  The unique design of the displays and electronics in the PRC* makes the outstanding battery life possible.  

*patent pending