Flooded Lead Acid Battery
There are various types of lead acid battery, these include gel cell, absorbed glass mat and flooded. The original lead acid battery dates back to 1859 and although it has been considerably modernised since then, the theory remains the same. Absorbed glass mat batteries and gel cell batteries are often grouped together as valve regulated lead acid (VRLA) batteries.
Lead acid batteries do not have great energy to weight or energy to volume properties, but they remain in use because they are cheap to manufacture and have excellent power to weight properties. Lead acid batteries are employed extensively in the automobile industry because they are capable of discharging a large amount of current in a short period of time; this is precisely what is required to put a static engine into motion (diesel or petrol etc.).
It is estimated that between 40-60% of the weight of an average lead acid battery is directly attributed to the lead plates (that is what it is so heavy).
Lead plates are suspended in electrolyte (water and sulphuric acid solution) within a plastic battery casing. Positive and negative plates are created with dissimilar coatings in order that current flows between them. As current flows between the plates due to chemical reaction, lead sulfate forms on both the positive and negative plates (lead sulfate appears as a yellow coating). As the lead sulfate increases, the voltage begins to decrease. The lead sulfate will crystallises upon the plates if a battery charger is not immediately connected and a charging current applied.