What are the causes of battery plate sulfation?
3 Answers
Plate sulfation (also known as plate sulfation or irreversible sulfation) refers to the phenomenon where, when a battery remains in a discharged state for an extended period, a layer of coarse-grained white lead sulfate crystals forms on the plate surface. These crystals are hard and difficult to dissolve, making them challenging to participate in oxidation reactions during charging. The main causes of battery plate sulfation are as follows: 1. Excessive discharge or deep discharge with small currents: Frequent excessive discharge or deep discharge with small currents causes lead sulfate to form in the inner pores of the active material, making it difficult to recover during normal charging. 2. Incomplete charging, frequent undercharging, or lack of periodic supplemental charging: Incomplete charging, frequent undercharging, or failure to perform periodic supplemental charging prevents the elimination of coarse crystal grains formed early on the plates. 3. Low electrolyte level during use: A consistently low electrolyte level exposes the upper part of the plates, preventing them from undergoing electrochemical reactions with the electrolyte and hindering full recovery of the active material. 4. Impure electrolyte, excessively high density, or high temperature: Impure electrolyte, excessively high density, or high temperature can also lead to battery sulfation.
Last year, I left my car parked for over two months during a business trip, and when I returned, it wouldn't start. The tow truck driver said the battery plates had sulfated. He explained that sulfation mainly occurs when the battery is left without charge for a long time, causing lead sulfate crystals to harden on the plates. It's like starving the battery, often caused by poor daily habits: such as leaving the car unused for too long, frequent deep discharges (e.g., forgetting to turn off headlights and draining the battery), low water levels not being topped up in time (especially in summer when water evaporates quickly), or only driving short distances without fully charging. I later learned that sulfation can reduce battery capacity by more than half, and if it fails to start, you'll need a costly and troublesome replacement. Now, I make sure to start the car and drive it around monthly or use a smart charger for maintenance, regularly checking water levels and voltage—small steps to prevent big problems.
I work in auto repair, and when customers have battery issues, nine times out of ten it's due to sulfation. The main causes are: first, the car sits idle for too long, and the battery naturally discharges to a depleted state; second, deep discharge goes overboard, like leaving the headlights on until the battery is drained; third, insufficient battery water levels, where evaporated water exposes the plates to air, accelerating lead sulfate crystal formation. Add to that insufficient charging—short trips don't allow the alternator to fully recharge the battery. Once sulfation occurs, the crystals harden, making them resistant to regular chargers, increasing internal resistance and causing startup struggles. Prevention is simple: don’t let the battery stay undercharged for long—fully charge it monthly; top up with distilled water if levels are low; in summer heat, ensure proper ventilation when parked. Use tools like a multimeter to check voltage—if it drops below 12.4V, charge it immediately.
