Battery Failure Modes

Battery Technology Reference · Last reviewed 2026-09-15

Direct answer: Lead-acid and lithium batteries fail through different mechanisms, but the pattern is the same — a specific abuse condition produces a specific chemical or physical degradation. Lead-acid fails mainly by sulfation, grid corrosion, water loss and stratification; lithium by SEI growth, lithium plating (and its dendrites) and, in the worst case, thermal runaway.

Lead-acid failure modes

Mode	What happens	Main cause
Sulfation	Lead sulfate crystals harden and stop converting back to active material	Chronic undercharging / stored discharged
Grid corrosion	The positive lead grid corrodes, raising resistance and shedding material	Overcharging, high temperature, age
Water loss / dry-out	Overcharge electrolyzes water into gas; electrolyte is lost (irrecoverable in sealed/AGM)	Overcharging
Acid stratification	Acid concentrates at the bottom of the cell, so plates wear unevenly	Partial charging, no gassing/mixing
Internal short	Separator failure or plate shedding lets plates touch	Vibration, deep cycling, age

Mode

What happens

Main cause

Sulfation

Lead sulfate crystals harden and stop converting back to active material

Chronic undercharging / stored discharged

Grid corrosion

The positive lead grid corrodes, raising resistance and shedding material

Overcharging, high temperature, age

Water loss / dry-out

Overcharge electrolyzes water into gas; electrolyte is lost (irrecoverable in sealed/AGM)

Overcharging

Acid stratification

Acid concentrates at the bottom of the cell, so plates wear unevenly

Partial charging, no gassing/mixing

Internal short

Separator failure or plate shedding lets plates touch

Vibration, deep cycling, age

Lithium failure modes

Mode	What happens	Main cause
SEI growth	The passivating layer thickens, consuming lithium and raising impedance	Time, heat, high state of charge
Lithium plating	Metallic lithium deposits on the anode instead of intercalating (irreversible)	Fast charge, cold temperature
Dendrite short	Plated lithium grows needle-like and can pierce the separator	Repeated plating
Over-discharge	Cell voltage falls too low; copper can dissolve and re-deposit as a short	Deep discharge below the cut-off
Thermal runaway	An exothermic chain reaction self-heats the cell to fire	Internal short, overcharge, external heat

Mode

What happens

Main cause

SEI growth

The passivating layer thickens, consuming lithium and raising impedance

Time, heat, high state of charge

Lithium plating

Metallic lithium deposits on the anode instead of intercalating (irreversible)

Fast charge, cold temperature

Dendrite short

Plated lithium grows needle-like and can pierce the separator

Repeated plating

Over-discharge

Cell voltage falls too low; copper can dissolve and re-deposit as a short

Deep discharge below the cut-off

Thermal runaway

An exothermic chain reaction self-heats the cell to fire

Internal short, overcharge, external heat

The common thread

Both chemistries are governed by the same truth: each failure mode has a specific trigger, and most triggers are operating conditions, not bad luck. Sulfation is undercharging; water loss is overcharging; plating is fast-and-cold charging. This is why the fix is usually a habit, not a hardware change.

The Author's Take

Position: The most useful way to read a failure-mode table is not to memorize it, but to see that almost every mode is a charging problem in disguise.

Reasoning: Undercharge sulfates, overcharge gasses and corrodes, fast-cold charge plates. Get the charging right and you have already avoided the majority of early battery deaths.

This is the author's editorial view, not a purchasing guarantee.

Sources

Battery Council International (BCI) — lead-acid failure-mode and maintenance references.

Peer-reviewed literature on SEI growth, lithium plating and thermal runaway.

Cross-verified with manufacturer technical literature (Yuasa, Canadian Energy, cell datasheets).