The easiest way to tell is to lift up the seat and look inside the battery area.  Look for the main negative wire coming off of the last battery in sequence(it will be the only negative wire not going to another battery).  If you have an OBC(on board computer) the wire will come off of that negative wire and through the middle of a small box about 4" inches square.  The small box is the OBC.  If your negative wire comes off of the batteries and directly to the motor or anywhere else it does not have an OBC.