How flat is your battery as the voltage drops?

We always have questions coming into us, generally along the lines of: “I have over 12 Volts reading on the meter for my car battery but it will not start the car and dies quickly?”This is a simple quandary and basically by the time the car battery Voltage is down to around 12 Volts it is only carrying around 25% of the charge that it would have when new and fully charged.  So, it’s quite simple: a 12 Volt car battery, at 12 Volts of charge needs replacing.

This little chart below shows the approximate charge as a % of that available compared to Voltage reaming.

100%       12.6 Volts
75%        12.4 Volts
50%        12.2 Volts
25%        12 Volts

I hope this explains one of life’s little oddities.