Q. I just spent $20, again, on batteries for my smoke alarm. The Duracell batteries I bought are good for five and 10 years. Is the old idea of replacing batteries every six months still relevant with the new-technology smoke alarms?—Ken Vanhoesen, South Walpole, MA
A. You have installed those smoke alarms in order to stay safe, and the battery-change schedule is conservative because of an abundance of caution. It’s true that a lithium 9-volt battery will probably last longer than an alkaline 9V (which in turn should last longer than a carbon-zinc 9V). But how much longer depends on a smoke alarm’s power drain. If you think that your alarm’s old battery has some “life” left, use it in a product that doesn’t have to do with safety. Or consider a switch to a newer model of smoke alarm with a lithium-ion power source that lasts 10 years.
Send your questions to ConsumerReports.org/askourexperts.
This article also appeared in the May 2015 issue of Consumer Reports magazine.
Copyright © 2005-2015 Consumers Union of U.S., Inc. No reproduction, in whole or in part, without written permission. Consumer Reports has no relationship with any advertisers on this site.