There are three ways to connect your lead acid batteries—parallel, series, and a combination known as series/parallel. We cover each of these battery configurations in greater detail in our Battery Basics tutorial section of the site should you want to delve in a little deeper or reinforce what you already know.
Normally, as the lead–acid batteries discharge, lead sulfate crystals are formed on the plates. Then during charging, a reversed electrochemical reaction takes place to decompose lead sulfate back to lead on the negative electrode and lead oxide on the positive electrode.
Electrode potentials and cell voltage for a typical flooded lead–acid battery As charging proceeds, the potentials keep gradually increasing until end of charge is reached. At this point, all lead sulfate is converted to lead on the negative electrode and to lead dioxide on the positive; and the charge is complete.
The discharge state is more stable for lead–acid batteries because lead, on the negative electrode, and lead dioxide on the positive are unstable in sulfuric acid. Therefore, the chemical (not electrochemical) decomposition of lead and lead dioxide in sulfuric acid will proceed even without a load between the electrodes.
The service life of a lead–acid battery can in part be measured by the thickness of its positive plates. During charging and discharging, the lead on the plates gets gradually consumed and the sediment falls to the bottom. As a result, the measurement of the plate thickness can be an indication of how much battery life is left.
One of the most important properties of lead–acid batteries is the capacity or the amount of energy stored in a battery (Ah). This is an important property for batteries used in stationary applications, for example, in photovoltaic systems as well as for automotive applications as the main power supply.