Question

Why do lead acid batteries discharge with time?

Answer 1

Lead-acid batteries discharge over time due to a few factors that affect their chemical and physical structure:

1. Self-Discharge: Lead-acid batteries naturally lose charge even when not in use. This happens because of internal chemical reactions, even if the battery isn't connected to any load. The lead plates inside the battery slowly react with the sulfuric acid, causing the battery to discharge. This process is called self-discharge.
   

1. Sulfation: Over time, if the battery is not kept fully charged, the lead sulfate (formed during discharge) on the plates can crystallize and harden, a process called sulfation. When this happens, it reduces the battery’s ability to accept and hold a charge, making it discharge faster.
   

1. Internal Resistance: As the battery ages, its internal resistance increases. This makes it harder for the battery to charge and discharge efficiently, leading to a gradual loss of capacity.
   

1. Environmental Factors: High temperatures or extreme cold can speed up the discharge process. Heat can increase the rate of chemical reactions inside the battery, causing it to discharge faster. Cold temperatures can make the chemical reactions slower, but also reduce the effective capacity of the battery.
   

1. Overcharging and Undercharging: If a lead-acid battery is overcharged or undercharged frequently, it can degrade faster. Overcharging generates heat, which can cause the electrolyte to evaporate, while undercharging can lead to sulfation, both of which accelerate the discharge process.
   

In short, a lead-acid battery discharges over time because of natural chemical processes, and environmental and usage factors that degrade its internal components. Proper maintenance, like keeping the battery charged and avoiding extreme temperatures, can help slow down this process.