1. Due to excessive discharge, prolonged disuse, or approaching the design lifespan, lead sulfate particles formed on the surface of the electrode plate are too large, resulting in decreased conductivity and loss of the ability to transform into active sponge like lead or lead dioxide;
2. Due to excessive discharge or physical impact, the active material on the electrode plate softens or falls off, falling into the bottom of the battery and forming unusable electrode sludge, directly leading to permanent reduction of active material and permanent decrease in battery capacity. When severe, the electrode plate may even crack.
3. Due to the evaporation of water during use, the electrolyte concentration becomes imbalanced, resulting in a decrease in the function and capacity of charging and discharging.
When lead-acid batteries are left unused for a long time (more than one month), the lead sulfate particles on the surface of the plates will gradually grow. Due to the non-conductive nature of lead sulfate particles, these grown lead sulfate particles have poorer conductivity and are difficult to revert back to active lead or lead dioxide, resulting in a decrease in capacity. This phenomenon is commonly referred to as sulfurization.
4. In addition, lead-acid batteries also experience gradually deepening sulfurization during normal use. Ultimately, batteries will become obsolete.