The facility repairing our post Antelope-strike damage managed to run the house and chassis batteries down to about 9.5v. The Optima Redtops are brand-new, but my 8D's are approaching 6-years. Haven't found any guidelines/cautions regards minimum charge levels nor risks of permanent damage. What do you battery experts think? I did have an "E-10" warning on the Heart Interface display, but when cycled during charging it went away.
Thanks!
Chad, If you go to this link, you will find about all you need to know about batteries I think.
http://www.dekabatteries.com/assets/base/0139EastPenn.pdf (http://www.dekabatteries.com/assets/base/0139EastPenn.pdf)