If it had to be jump started then the battery was very low.
The second time it wouldn't start indicates that the battery is not good.
A fully charged battery would be 12.6 volts @ 2.1 volts per cell 6 cells in a normal car battery. 14 volts would be fine as a charging voltage, however it would not be battery voltage.
It may show as battery voltage IF the engine has been running and was just shut off prior to the test. This is called "surface charge" it is the result of the sulfuric acid and lead sulfate conversion that takes place while charging. The conversion takes place at around 14-15 volts, it is also delayed some from the charging cycle so that you remove the charging voltage and you can read a "battery" voltage equal to that voltage.
This doesn't tell you the real story about the batteries condition though and can lead to many saying "the battery is good", when in reality it isn't.
Tuesday, August 29th, 2017 AT 10:16 AM