I have a Husqvarna lawn tractor 48

When your tractor is running check the voltage at the battery posts with a meter. If the voltae is above 12 you are chrging good and need to replace the battery. If it is lower than 12 then the regulator and altinator are next. Remove the regulator and you will find numbers on it to take to a dealer and replace or have checked. Do the same with altinator..it could be either so give it your best guess in the order you want to have them checked. On a personal note..check your ground wire from battery to frame and make sure it is tight and clean. :) Hope this helps.