From time to time, we all check the condition of our batteries; whether we have a meter, dial or LED monitor. What is not known quite as widely is that battery performance is exponential, which is just a fancy-dancy way of saying that a read-out of 6 volts does not mean that a 12V battery is half dead.

Here's a little chart to explain:

12.66V=100%
12.45V=75%
12.24V=50%
12.06V=25%
11.89V=Discharged

Here's another way of looking at it:

100%=1.265 Specific Gravity
75%=1.225 Specific Gravity
50%=1.19 Specific Gravity
25%=1.155 Specific Gravity

All of the above are calculated at 80F degrees or, 26.7C degrees.

Correction factors are significant, depending upon the ambient temperature of the location of the battery.

For example, if it is 90F, a correction factor of +4 is indicated.

If ambient temperature is 50F, a correction factor of -12 is indicated.

Although many of us may think that minor battery fluctuations are insignificant, they are not.