34
\$\begingroup\$

I recently measured a brand new Duracell AA battery which is labeled as 1.5 V. The reading was 2.3 V. Is this ever normal for a fully charged battery, or is my multimeter broken?

\$\endgroup\$
  • 4
    \$\begingroup\$ no, a fully charged AA should be about 1.6. maybe if the cell was over-heated it could produce 2.3 but the smart bet is on a wanky meter. \$\endgroup\$ – dandavis Jun 6 '17 at 9:02
  • 1
    \$\begingroup\$ Now you know you need a better multi-meter if you want measurements you can trust. Yours seems to be defective by design. \$\endgroup\$ – Dmitry Grigoryev Jun 6 '17 at 10:08
  • \$\begingroup\$ What kind of battery is it? Alkaline? "Alkaline batteries account for 80% of manufactured batteries in the US" \$\endgroup\$ – Peter Mortensen Jun 7 '17 at 8:55
  • 1
    \$\begingroup\$ Yes, it's alkaline. \$\endgroup\$ – merlin2011 Jun 7 '17 at 9:01
  • \$\begingroup\$ There are a few inexpensive DVMs that give high voltage readings when measuring DC voltage with the meter set to measure AC. \$\endgroup\$ – Peter Bennett Mar 12 '18 at 6:21
66
\$\begingroup\$

Most likely cause is that you need to replace the battery in your multimeter.

When the battery is very weak, the voltage drops to the point where the internal reference can no longer maintain regulation and it, in turn, also drops. A low reference voltage results in a high reading, which is exactly what you are seeing.

Usually there will be a low battery indicator in the display, but you may have not noticed. Personally, I think the display should be blanked rather than display an erroneous reading, but many meters do not do that.

\$\endgroup\$
  • 18
    \$\begingroup\$ I audited my half-a-dozen meters for low battery, when the warning comes on, when the reading goes bad, when the display blanks, and was horrified. If you have more than one meter, and a variable power supply, it's an exercise worth doing. The cheapo ones are not necessarily the worst! \$\endgroup\$ – Neil_UK Jun 6 '17 at 9:20
  • 4
    \$\begingroup\$ I have an analog scope that I was using to measure resistance but got different readings for the same resistor at different multiplier settings. Changing the battery also fixed that. \$\endgroup\$ – MichaelK Jun 6 '17 at 12:11
  • 42
    \$\begingroup\$ @Neil_UK It's like a twist on the clock saying: "A man with one multimeter knows what the voltage is, but a man with many multimeters is never quite sure" \$\endgroup\$ – W5VO Jun 6 '17 at 13:26
  • 4
    \$\begingroup\$ @W5VO I thought that was about compasses. \$\endgroup\$ – a CVn Jun 6 '17 at 14:27
  • 4
    \$\begingroup\$ @MichaelKjörling, It is about measurement. Period. (but clocks are certainly oft mentioned.) \$\endgroup\$ – hildred Jun 6 '17 at 15:47

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.