A lead-acid battery (VRLA) is a battery whose electrodes are mainly made of lead and its oxides, and the electrolyte is a sulfuric acid solution. In the discharge state of the lead-acid battery, the main component of the positive electrode is lead dioxide, and the main component of the negative electrode is lead; in the charged state, the main component of the positive and negative electrodes is lead sulfate.

The nominal voltage of a single-cell lead-acid battery is 2.0V, which can be discharged to 1.5V and charged to 2.4V; in applications, 6 single-cell lead-acid batteries are often connected in series to form a nominal 12V lead-acid battery , and 24V, 36V, 48V, etc.