Many people feel that when the battery on the car is out of order, when the battery pack is removed and opened, the battery will have a drum kit, and sometimes it will be severely deformed Longitudinal look at some of these cells in the year, some even during the warranty period, why is this so? Actually there is nothing special this mysterious thing, or not? And then look down, two minutes is enough: Reason one: when charging the battery is the lead sulfate on the positive and negative plates and the water in the electrolyte chemical reaction, thus make the positive plate back into lead oxide, negative plate back into pure lead.