A lead-acid battery can fail for many reasons, such as sulfation, water loss, thermal runaway, shedding of active material, and plate softening. Here we explain sulfation and water loss in detail.

The charging and discharging of a lead-acid battery is an electrochemical process: during discharge it forms lead sulfate, and during charge the lead sulfate is reduced back to lead oxide. Under normal conditions this electrochemical reaction is a reversible cycle, but lead sulfate is a salt that crystallizes easily. When the concentration of lead sulfate in the battery electrolyte is too high or the battery sits idle for too long, the particles clump together into small crystals, and these crystals attract more lead sulfate around them, growing like rolling snowballs into large, inert crystals. This destroys the originally reversible cycle and makes part of the lead sulfate irreversible. Once crystallized, the lead sulfate not only cannot be reduced back to lead oxide during charging, but also adheres to the grids, reducing the working area of the grids and lowering the capacity of the lead-acid battery. This phenomenon is called sulfation.

One of the basic principles of a sealed lead-acid battery is that after oxygen is released at the positive plate, it goes directly to the negative plate and is reduced with the hydrogen released there back into water. The parameter used to assess this technical index is called the seal reaction efficiency, and this phenomenon is called the oxygen cycle. In this way a lead-acid battery loses very little water and becomes maintenance-free, that is, needing no water refill. High-current discharge and long disuse lower the oxygen-cycle ability of the negative plate and cause the battery to lose water, and after water loss the battery is left with a higher proportion of sulfuric acid, which effectively raises the specific gravity of the acid and makes the lead-acid battery more prone to sulfation. So in a lead-acid battery, sulfation worsens water loss, and water loss in turn worsens sulfation.

In the end, the main causes of battery failure are two: human factors and the battery itself.

1. For human factors, we should maintain the battery more carefully in daily use.

2. For the battery itself, we should choose carefully and go for a high-quality battery from a well-reputed brand, such as Xupai battery. Xupai batteries are very solid in quality with good service, and its sales, customer service, technical support, and repair systems are well developed, giving consumers better after-sales service.