Technical info - Stratificaton


In a lead acid battery the electrolyte is a mixture of water and sulfuric acid. Stratification occurs when the water and acid separate, so that the heavy acid is concentrated on the bottom, causing the upper half of the cell to be acid poor. The upper part of the battery plate will sulfate because of depleted electrolyte, and the lower section will succumb to mass loss and grid corrosion due to overcharge!

Stratification occurs if a battery is kept at a state of charge of less than 80% and never have the opportunity to receive a full charge. That may be the result of self-discharge in combination with long-term storage, but also in situations like short distance driving while running windshield wipers and electric heater.

Stratification can be remedied by an equalization charge: the gassing induced by the high charging voltage will mix the electrolyte.

Not in VRLA

Valve Regulated batteries contain immobilized electrolyte and as a result, this phenomenon will not occur in gel batteries. In AGM batteries stratification will only occur in very tall stationary batteries. These batteries are usually fitted in tilted position.