From experience If the battery is below its stated voltage eg 1.5v it needs replacing.
Yes, but a cell with an open circuit voltage equal to specification might also need replacing, so just getting 1.5V on a meter with no load is not definitive, even if getting 1.2V on a similar test is.
Yes, but a cell with an open circuit voltage equal to specification might also need replacing, so just getting 1.5V on a meter with no load is not definitive, even if getting 1.2V on a similar test is.