The electrolyte of a stratified battery concentrates at the bottom, starving the upper half of the cell. Acid stratification occurs if the battery dwells at low charge (below 80 percent), never receives a full charge and has shallow discharges.
Allowing the battery to rest for a few days, doing a shaking motion or tipping the battery on its side helps correct the problem. Applying an equalizing charge by raising the voltage of a 12-volt battery to 16 volts for 1–2 hours also helps by mixing the electrolyte through electrolysis. Topping charge is applied to maintain full charge and to prevent sulfation on lead acid batteries.
The stratification of the acid can cause loss of capacity and / or battery failure.