Accumulation of sulfuric acid at the bottom of the cell is called acid stratification. It can lead to faster sulfation, reduced capacity, and hence eventually battery failure. As a lead acid battery owner, you must know the details of acid stratification.
Causes of Acid Stratification
As you know, lead acid battery electrolyte is a mixture of water and sulfuric acid. Sulfuric acid is heavier than water. So, when the battery is not in use, the acid tends to settle down at the bottom of the cell. Stratification also occurs if the battery charge is regularly around 80-85%, not fully charged. This can happen if you use your car for driving short distances.
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Effects of Acid Stratification
When a battery is in storage, there is more sulfuric acid at the bottom, and the bottom part of the lead plates start sulfating faster and to a greater degree than the rest of the plates. The low concentration of acid at the top induces higher corrosion and lesser plate activation. At the bottom, due to higher concentration of ions, open circuit voltage is artificially increased. It is called artificial because the readings show high voltage but the battery cannot actually take that much load. In automobiles this can lead to loss in CCA (Cold Cranking Amps) performance.
Tackling Acid Stratification
What do you do when the sugar in your sugar syrup settles on the bottom? Give it a good stir, right? Here also, you can shake or tilt the battery to mix its electrolyte well. A better way is to give it an equalizing charge for a couple of hours. Equalizing charge is charge that is 10% higher than the recommended charge level. It induces electrolysis, which mixes the electrolyte well.
In lead acid batteries, acid stratification is a problem if you use your battery for small durations, like city driving during cold months, while using all the power-hungry gadgets for short distances. AGM batteries don’t suffer from stratification problems, so you can use them if your budget allows it. Otherwise, just care for your current battery by charging it to full capacity regularly.
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