On my zmax when it is set to 11watts and I fire it with a fully charged battery it shows 11watts, but as I use the unit and the battery charge drops, so do the watts. First it goes tp 10.3 then 9.8 and so on.  Is this normal or do I have a defective unit?  I am using a kayfun with a 1.7 coil.  I had the unit usually set to display resistance so I dont know if it was doing it all along. 
Thanks for any help.
	
		
			
		
		
	
			
			Thanks for any help.