About a year before I was put in charge. They gave me several shifts to orient to the charge position with someone else.
There always has to be at least 2 charge capable RNs on at one time in case of emergencies, unexpected events, and as a resource for the acting charge nurse (sometimes two heads are better than one when issues come up).
Charge nurses on my unit don't take a patient assignment unless there is a major staffing issue, in which case we usually call our NUM or assistant NUM to come in and staff (however when that happens they usually pull rank and put us into staffing and take over being charge).
But just because the charge RN's on my unit dont take pt's doesn't mean we sit back and hang out. Our responsibilities include: carrying the rapid response team beeper, being a resource for the rest of the staff, helping with new admits, turning, bathing, traveling, order entry if we don't have a unit clerk, plan the staffing for the next shift, balancing the staffing numbers for the current shift based on the staffing grid, doing little busy-work assignments like stocking rooms and organizing things, .... Sounds like alot, and it is, especially for only an extra dollar an hour :-) Sometimes I feel more tired after a night of doing charge than if i took an assignment.