When I checked a new coin cell battery with a battery tester, the voltage was lower than the nominal voltage. Is this normal?

2 November 2021

It depends on the battery tester you are using, but in the case of an analog tester, it is not possible to measure correctly because it does not match the characteristics of the battery because it measures while passing a large current. Even among the devices sold that can measure button batteries, it may not be possible to measure correctly with devices that measure using the same principle.
Generally, use a measuring instrument called a digital multimeter (tester) or digital voltmeter, and measure with an input resistance of 1 megaohm or more.

Select your currency