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What Happened To Duracell PowerCheck?
(hackaday.com)
This is a most excellent place for technology news and articles.
I never had any issues with them. You can't expect a real accurate calibration, but it beat trying to find a tester to see if it was a new battery or kaput.
I tried rechargeables in the 90s and was not impressed. I hadn't realized they are better now. Will have to give them another go. These powercheck strips would still be very applicable to rechargeables too.