Re: Nine Year Quartz Clock Battery?
View attachment 402219
This is a preliminary update to my post #53 speculating that a lithium AA cell might power my small German travel alarm clock for 9 years. The lithium battery, installed on Feb 20, 2012, at 5 years on February 20, 2017 was still powering the clock as of today, February 27, 2017. I did not check the initial voltage of the battery but I recently checked two new Ultimate AA lithium batteries to get an average voltage of 1.833 volts dc open circuit. The 5 year old battery in the clock presently measures 1.758 vdc oc.
According to a graph on Energizer's web site,
http://data.energizer.com/PDFs/lithiuml91l92_appman.pdf , a new Ultimate Lithium cell has an open circuit voltage of 1.8 vdc that immediately drops to about 1.72 vdc with an applied 1 ma. load. The graph shows a lithium battery depleted down to 1.4 volts as having a sharp voltage dropoff after that. It seems fair to believe that the clock will run for a while after 1.4 volts because the clock will still run at 1.35 vdc as determined with a nearly depleted alkaline cell.
The meter that I used was a Velleman DMM that some time ago I was able to compare to a Beckman DMM that had been calibration checked against a standard traceable to NIST. Using the two volt dc scale the 20 dollar Velleman meter showed good accuracy as it measured only 0.4% higher voltage than the Beckman. It is possible, of course, that the Beckman meter was not perfectly accurate as is so with any meter. This is the best that I can do regarding voltage accuracy without spending some money to have my Velleman DVM850BL checked at a scientific instrument calibration facility.
Conclusion: At 1.758 vdc oc, the Ultimate Lithium AA battery voltage is still very near the voltage when new so it appears possible as of now that the battery will continue to run the clock to 9 years. Time will tell, so to speak.