Electrolyte Solutions in Lead-Acid Accumulators
Composition and Properties
The electrolyte solution in a lead-acid accumulator primarily consists of diluted sulfuric acid (H2SO4) in water (H2O). The concentration of the sulfuric acid is a crucial factor determining the battery's performance and state of charge. Higher concentrations generally lead to increased conductivity and electrochemical activity, but also to increased corrosion rates.
Electrochemical Reactions
During discharge, sulfuric acid is consumed as it reacts with the lead plates (Pb) to form lead sulfate (PbSO4) on both the positive and negative electrodes. Water is produced as a byproduct. The reverse process occurs during charging, regenerating sulfuric acid and consuming water.
Concentration and State of Charge
The specific gravity of the electrolyte solution is directly related to the sulfuric acid concentration and serves as an indicator of the accumulator's state of charge. A higher specific gravity indicates a higher concentration of sulfuric acid and a higher state of charge. Hydrometers are commonly used to measure this specific gravity.
Safety Precautions
Due to the corrosive nature of diluted sulfuric acid, appropriate safety measures must be taken when handling the electrolyte. These precautions include wearing protective gloves, eye protection (goggles or face shield), and acid-resistant clothing. In case of contact with skin or eyes, immediate and thorough flushing with copious amounts of water is essential, followed by seeking medical attention. Neutralization with a weak base may also be considered.
Effects of Temperature
Temperature significantly influences the performance of lead-acid accumulators and the properties of the electrolyte. Lower temperatures decrease the ion mobility and electrochemical reaction rates, reducing the battery's capacity and power output. Higher temperatures can accelerate corrosion and self-discharge rates, potentially shortening the battery's lifespan. The specific gravity reading must be temperature-compensated for accurate state-of-charge assessment.
Electrolyte Maintenance
Regular maintenance of the electrolyte involves checking the specific gravity and adding distilled or deionized water to compensate for water loss due to electrolysis and evaporation during charging. Maintaining the correct electrolyte level is crucial for optimal performance and longevity of the accumulator. Overfilling can lead to electrolyte spillage and corrosion.