What do you mean my "discharge"? If you mean total charging volts drop a bit, yes, that's normal.
You should be getting 12.8 volts or higher at idle, and they should go up to around 14.8 when the engine is spinning faster.
Well that's an interesting story. I was having problems with occasionally weak/low battery so I installed a voltmeter. It showed voltage 13.5-14 but sometimes 11 at cruise. So as a test I tossed in a $20 regulator just to see what happens. Now I'm generally not less than 13.5 but I've seen 16. Its odd that its not consistent.How many volts at 5000?how old is the battery?