Mike McCarron wrote:
Help!

I have carefully measured my current draw in my glider at .8 amp. l would
like to know if there is any reasonable explanation for why a 9 amp hour
battery goes from 13 volts open circuit fully charged to 11.6 volts in 4
hours.

Short answer: 9AH is the nominal capacity, the actual capacity
depends on temperature, discharge rate and battery age..

Long answer: have a look at the graphs in, for example,
http://www.standbattery.com/linkfiles/Technology%20Manual.pdf