Car maintenance: introduction of battery-related details

The battery is the main energy storage device on the car, which provides electricity for all the electronic systems on the car. Modern cars are becoming more and more electronic, and the lack of battery power will cause the entire car to be paralyzed.

Type of battery:

The batteries used in general cars are lead-acid batteries. There are two types of common lead-acid batteries, one is water-added lead-acid batteries, and the other is maintenance-free lead-acid batteries.

Water-added lead-acid batteries: The plates of ordinary batteries are made of lead and lead oxides, and the electrolyte is an aqueous solution of sulfuric acid. Its main advantages are stable voltage and low price; its disadvantages are low specific energy (that is, electric energy stored per kilogram of battery), short service life and frequent routine maintenance.

Maintenance-free lead-acid battery: Due to its structural advantages, the maintenance-free battery consumes very little electrolyte and basically does not need to be supplemented with distilled water during its service life. It also has the characteristics of shock resistance, high temperature resistance, small size, and small self-discharge. The service life is generally twice that of ordinary batteries. There are also two types of maintenance-free batteries on the market: the first one is that the electrolyte is added once at the time of purchase and does not require maintenance (addition of supplementary fluid) after use; the other is that the battery itself has been filled with electrolyte and sealed up when it leaves the factory. , The user cannot add refill at all.

Battery maintenance method:

The capacity and discharge capacity of car batteries will decrease after being used for more than 2 years. The life of a general car battery will not exceed 4 years. Of course, a well-maintained battery will last longer. Let’s learn about the maintenance methods of water-filled lead-acid batteries and maintenance-free lead-acid batteries.

Water-added lead-acid battery: Pay attention to battery liquid level and battery liquid density.

The battery fluid of lead-acid batteries is a mixture of sulfuric acid and distilled water. When the battery is discharged, the water will increase and the sulfuric acid will decrease, which leads to the decrease of the battery fluid density; when charging, on the contrary, the water will decrease and the sulfuric acid will increase. The battery fluid concentration reflects the ratio of water and sulfuric acid in the battery fluid. The normal electrolyte density is 1.28 (summer)/1.29-1.30 (winter) (unit is grams per cubic centimeter).

As car owners, we should check the battery level regularly. When the battery fluid is insufficient, add distilled water to the proper level. After adding distilled water to the battery, we should check the battery liquid density and keep the battery liquid density within a reasonable range at all times.

Maintenance-free lead-acid battery: Regularly check the magic eye and keep the battery fully charged

Because the maintenance-free battery does not have a water filling hole and a battery level scale. We need to judge the state of the battery through the “magic eye” on the battery. The magic eye is green to indicate that the battery is normal and fully charged; the magic eye is black to indicate that it needs to be charged; the magic eye is white to indicate that the battery needs to be replaced.

The discharge capacity needs to be tested with a dedicated battery tester.

We generally use a voltmeter to check the battery voltage. Although we can detect the voltage value of the battery, we cannot check the load capacity of the battery. In order to check the actual condition of the battery, we should use a dedicated battery tester to check the battery’s discharge capacity and load capacity.

The weak current cannot be ignored:

After the car is locked, the anti-theft system of the vehicle starts to work and draws a weak current from the battery. Therefore, the battery will be short if the car is not used for a long time. If the vehicle is found to be short of power when it is stationary for a short period of time, in addition to checking the battery condition, it is also necessary to check whether the weak current of the vehicle is too large when it is standing still. The weak current when the vehicle is standing still may be caused by the partial grounding of the electrical circuit in the vehicle. If it is not handled early, it will cause safety hazards. At the same time, excessive discharge of the battery for a long time will also shorten its life. The auto repair industry generally uses a clamp-on ammeter to detect the weak current when the vehicle is standing still.

What should I do if the battery freezes?

Since the battery fluid in the battery is water and sulfuric acid, the battery is likely to freeze at low temperatures. What should I do as a car owner if the battery freezes?

First of all, let’s not study whether the battery fluid in the battery will freeze, let’s first take a look at what should we do when the battery freezes?

After the battery freezes, our vehicle will not start. We should remove the battery from the car, and then move it to a heated place indoors to melt the battery liquid before loading it into the car for use. Of course, removing the battery at night and storing it in a warm place in the house can prevent the battery from freezing.

Will the battery freeze?

The battery will freeze under the following conditions:

1) Adding too much distilled water causes the density of the battery liquid to decrease. At this time, the percentage of water in the battery liquid increases and the freezing point of the battery liquid rises.

2) Excessive discharge causes the density of the electrolyte to decrease, and the imbalance of the ratio of sulfuric acid and water makes the freezing point of the battery liquid rise.

What is the freezing point of the battery electrolyte?

The normal sulfuric acid concentration of a battery is 35%-40%. According to the “freezing point curve of sulfuric acid-water mixture”, we can know that the freezing point of the electrolyte is between -60 degrees Celsius and -50 degrees Celsius. From the data point of view, as long as the battery liquid density is maintained between 1.25-1.30, the possibility of icing is unlikely (unless you use a car in a very northern part of China).

However, as the concentration of sulfuric acid decreases, the freezing point of the battery fluid rises, which makes the battery fluid possible to freeze. For example, the lowest temperature in Beijing in winter is generally more than ten degrees below zero. When the battery liquid density is as low as 1.10, the battery may freeze. The most common cause of the above changes is over-discharge of the battery.

How to avoid excessive battery discharge:

1) Avoid using high-power electrical appliances when parking and waiting. High-power electrical appliances include headlights, fog lights, seat heating, audio and air conditioning.

2) Check whether the headlights and the roof lights in the car have been turned off before parking and leaving. Generally speaking, a normal fully charged battery can keep the headlights working for two hours. As the rated capacity of the battery decreases, the time for the headlights to work normally becomes shorter. If you forget to turn off the headlights after parking and leaving, the vehicle’s computer does not automatically turn off the lights, and the probability of not being able to get on the car the next morning can reach 99%.

3) If the vehicle is not used for a long time, the negative electrode of the battery should be unplugged. Due to the weak current consumption in the circuit system of the vehicle when parking, leaving the vehicle for a long time will cause the battery to run out. Therefore, for vehicles that are not used for a long time, we should unplug the negative electrode of the battery to avoid excessive battery power consumption.

Final Thoughts

In most areas of China, a lead-acid battery in good condition will not freeze. Car owners and friends should pay more attention to the battery of the vehicle and check the battery condition regularly to avoid excessive discharge of the battery. If the service life of the battery is up, and it is found that the vehicle is difficult to start, and the headlights are not bright, we recommend that the owners replace the battery as soon as possible.

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