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[Beau388]

Originally Posted by ScottyB410

Well,

An everyday lead acid battery, whether deep cycle or starting, has a nominal voltage per cell of ~2.1 VDC. Therefore, a fully charged 6 cell battery will show a voltage of ~12.6 volts. Period.
although certain batteries might show 12.7 or 12.8, the basic chemistry of the battery does not allow it to rise beyond that.

If you are looking at your volt meter, and it is showing 13.1 or 13.6 (or some at 14.2), you are looking at the voltage being output by the charger, not the voltage held in the battery. To charge a lead acid battery, the charger will output between 2.25 for fast charge then reduce to 13.1-13.5 (know as a float charge)

If you are checking the battery's state of charge, you need to be aware of a physical condition known as a surface charge. During the last minutes of the absorptive stage of charging, the conversion of lead sulfate to lead and lead dioxide is a very slow process. During this process, hydrogen is absorbed into the sulfuric acid. This process causes the battery to act like a big capacitor and take a non-chemical charge. This effect will show a voltage of 12.8 to 13.2 volts depending on the temperature of the converter or battery temperature probe if one is installed. This charge will gradually dissipate over several hours or it can be used by turning on the lights for a couple minutes. If the batteries were discharged and recharged to about 90% of capacity, removing the charger and immediately checking the voltage will read above 12.7 volts. Thus the battery voltage should only be checked after the battery has rested for several hours after charging (24 hours is the recommended resting time) or after the surface charge is drawn off the batteries by using some electrical device for several minutes with the charger removed.