The charging system of the car
Because the battery consumes sulfuric acid in the discharge process, generated water, so the density of the electrolyte in the discharge process is gradually decreased, when the battery is completely out of power, the density of the electrolyte also decreased to the lowest. We can roughly know the discharge degree of the battery by measuring the density of the electrolyte, which is also the principle of the maintenance-free battery power observation hole. Generally, the electrolyte density of the fully charged battery is about 1.28g/ml, and the electrolyte density of the battery without electricity is about 1.24g/ml. And fully discharged battery electrolyte freezing point will rise, in the cold winter there is a risk of freezing.
The parameter that characterizes the battery capacity is the rated capacity. The so-called rated capacity is the capacity of the battery output by discharging a new fully charged battery at an average temperature of 30°C at a continuous discharge rate of 20h until the voltage of the battery is reduced to 10.5V. For example, the type of battery commonly used in our cars is 6-QA-60, where "60" is the rated capacity, which is obtained by discharging the current of 3A for 20 hours continuously and the battery voltage dropping to 10.5V. Generally, the higher the capacity of the battery, the more active substances such as positive and negative plates and electrolyte inside, the larger the volume, and the higher the cost. Nowadays, in order to reduce the cost, cars usually use smaller batteries, such as 6-QA-60 replaced by 6-QA-45. The volume and rated capacity of the battery are reduced, and the cost is also reduced. However, such batteries are not durable.
