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I have a notebook main battery labelled HP (Hewlett Packard) CM03XL 716724-422 and 11.25 V and lithium-ion. This battery is a few years old.

The measured output voltage is 13.0 V. Seems to be quite a high reading. What is going on here?

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  • \$\begingroup\$ Are you sure your meter is in calibration? My cheap Harbor Freight DMMs read high when the battery is low. \$\endgroup\$
    – PStechPaul
    Aug 18 at 22:45
  • \$\begingroup\$ Have you tried measuring a fresh "1.5V" AA battery? Fully charged/new batteries usually read high. As they discharge, the cell voltage goes down - to a varying extent, depending on battery chemistry and ratings. \$\endgroup\$ Aug 18 at 22:46

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A 11.25V rating implies a 3 cell series battery. They use the nominal lithium-ion cell voltage of ~3.7V when they make the rating (3 * ~3.7V = ~11.1V).

A lithium-ion cell's fully charged voltage however is ~4.2V. So, when fully charged, the battery voltage can be as high as ~12.6V

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