From jjmcs49@yahoo.com Tue Oct 13 12:04:57 2009
Subject:Re: XK-1 replacement battery type?

The early production XK-1's detected low batteries before they were too low. As I understand it, some batteries may slowly drop in strength at a fairly constant rate so it may take 3 years (for example) to reach 40% and others may drop to say 45% in 1 year. The second battery may take 3 more years to go down to 40%. The charge monitoring circuit was set to trigger the warning at say 46%. The circuit was adjusted to trigger the warning at a lower charge level. The numbers I used are guesses to explain the concept not the actual circuit parameters.