Definition
A condition that develops in a lead-acid battery when it is left in a discharged state for an extended period. Lead sulfate, which forms normally on the plates during discharge, hardens into large crystals that no longer dissolve back into the electrolyte during charging. This permanently reduces the battery's capacity and ability to hold a charge.
Plain English
Damage that happens to a lead-acid battery when it sits flat for too long. A crusty buildup forms on the inside plates and won't go away, leaving the battery weaker than it used to be.
Context Anchor
Seen in aircraft battery maintenance, charging, storage, and troubleshooting discussions.
Derivation
From sulfate, the chemical compound (lead sulfate) that forms on the battery plates. The 'ing' ending indicates an ongoing process — the battery is progressively becoming sulfated.
Why Pilots Care
Sulfation reduces battery capacity and can cause starting failures or sudden electrical loss if the battery is not properly maintained or replaced.
Analogy
It is like a buildup forming on a tool’s working surface. The tool is still there, but the buildup keeps it from doing its job well.
Intuition Check
Sulfating does not mean the battery has simply touched sulfur or acid. It means a sulfate buildup has formed on the battery plates and is reducing battery performance.
Example Sentence 1
The mechanic found the battery had been sulfating after the aircraft sat unused for three months over the winter.
Example Sentence 2
Using a proper smart charger prevents sulfating and keeps the aircraft battery ready for reliable engine starts.