Asking this for my parents. They have a ZTR with a 23hp Kohler command, vert. shaft, 2001/2002 model year, that has quit charging the battery. It's not putting out power at all. They have to charge the battery with a charger to have power to keep the blade clutch engaged. Once the power in the battery runs down while mowing the clutch eventually won't stay on and he has to put the battery back on the charger and wait... What's the charging system on these engines, where is it, and how do you replace it? Thanks!