Duracell Procell Alkaline Batteries, 9V, 12/Box

I've used Duracell Procell 9V batteries as the backup batteries for my hardwired smoke/CO detectors for many years. I try to replace them every 2 years before the winter because I hate getting woken up in the middle of a cold night to a smoke detector chirping from a low battery. These discharge inconsistently and after sitting in the detectors for 2 years, some will have barely lost any charge (-0.1-0.2V) and some will have gone down by 0.5-0.7V. I've kept track and it's never the same detectors discharging faster. Any battery that's being used for smoke detectors really should be checked with a multimeter first. I just got a box from a third party seller that expires in less than 1 year after the purchase date. The expiration date is usually at least 4 years into the future. I didn't notice and stupidly installed them without checking them first. Two of my 10 smoke detectors started giving a low battery chirp within 30 minutes. I pulled them all and found that more than half were reading less than 9V! The rest were just barely above 9V. Nowhere near a full charge for these batteries and completely unusable for smoke detectors. The box was pristine and the batteries were obviously unused (the black terminal guards were very snug), so I bet these sat in some warehouse in extreme temperatures for years before someone noticed they hadn't been sold and pulled them for my order. I'm not going to name the seller because it could happen with any of them and honestly don't remember if was a "fulfilled by Amazon" item or not. Just a word of warning that you should check all of these while you're still in the return window and don't accept anything with a quickly-approaching expiration date. EDIT: Received new batteries from a different seller with an expiration of 4 years and 11 months into the future. These are manufactured with 5 year expiration dates, so they are as fresh as I've ever received. The batteries have been redesigned, now all in black and branded with "PROCELL" and no mention of Duracell anymore. The voltage of each battery measured between 9.9-10.0V. If you are still getting the yellow "PROCELL by Duracell" packaging after early 2020, you are getting old stock and should be weary of their charge.