These processes must not be forgotten when replacing the car battery

Replacing batteries is a common occurrence in auto repair shops and car owners' lives. Today, we share this article to introduce in detail how to replace the battery.

1. Remove the old battery

(1) Confirm the battery installation location. Most of cars are installed in the engine compartment or luggage compartment, although some cars are installed near the driver's seat. And protection measures will be taken at the corresponding positions.

(2) Remove external protection devices such as the battery protective cover, measure the voltage between the two terminals with a multimeter, or check the battery status through the observation hole, and explain these conditions to the customer.

(3) If the car has an anti-theft system (including audio anti-theft), you can connect an external power supply first, or connect a battery with sufficient power in parallel. Pay attention to connect the positive terminal first and then the negative terminal. The positive terminal of the external power supply can be directly connected to the positive terminal of the battery, but the negative terminal should not be directly connected to the negative terminal of the battery, but should be connected to the put-up iron position.

(4) Turn off the ignition switch of the faulty car (Some models need to be placed in ON gear, such as Volvo S80 produced before 2005, etc., refer to the maintenance manual), first disconnect the negative wire of the battery, and then disconnect the positive wire. If the battery has vent tube, remove it first.

(5) Remove the fixing device and take out the battery. If the car is connected to an external power supply, be careful not to let the positive wire come into contact with the car, and isolate it with cotton cloth.

(6) If the old battery has leakage and corrosion, it is also necessary to clean the battery connection wire.

2. Install a new battery

(1) Before installing a new battery, if the brand and model of the battery are not the same as the old one, compare the external dimensions and terminal positions of the new and old batteries, and carefully check the battery capacity and cold-start current parameters. Especially in the winter, if the cold starting current does not match, it may cause difficulty in starting the car.

(2) If conditions allows, use a battery tester to test the battery. After some batteries have been placed for a long time, although the voltage between the positive and negative electrodes is higher than 12V, the actual capacity is not enough, which is the so-called "virtual power". Such batteries need to be charged. It should be noted that the measurement must be performed when the ambient temperature is higher than 0°C, and the charging must be performed when the ambient temperature is higher than 5°C.

(3) Place the new battery in the installation position and fix it. For those batteries with vent tube, don't forget to remove the vent tube connector from the old battery and install it on the new battery. For lead-acid batteries, it should be noted that the inclination angle of the battery during installation should not exceed 30°.

(4) When connecting the battery wiring, connect the positive terminal first, and then connect the negative terminal. After installation, you can spray anti-rust protective agent or acid-free grease on the battery terminal for protection.

(5) After checking and confirming that the fastening is reliable, the external power supply can be removed. Start the engine and check the generator voltage, which can be measured at the generator output side or on the battery terminal. If there is special diagnostic equipment, the voltage data in the data stream can also be read. In addition, it is recommended to measure separately at engine idle speed and 2000 r/min.

(6) For cars whose batteries are replaced due to discharge failure, the quiescent current of the car should also be checked. The traditional method is to put the multimeter in the current block, then connect it in series to the negative line of the battery, lock all the door locks, turn off the ignition switch and activate the anti-theft system, and let it stand for a period of time until the current is stable.

(7) For the car equipped with a power management system, a sensor will be installed in the negative line, we can only use device such as clamp ammeter for current testing. Generally speaking, the quiescent current of the car should be less than 50 mA (subject to the maintenance manual, for example, some BMW car only require less than 80 mA).

(8) After replacing the battery, the diagnostic instrument should be used to clear the relevant trouble codes recorded in the system. For those cars equipped with a power management system, such German brands as Mercedes-Benz, BMW and Audi, it is also necessary to input the model of the new battery in the power management system and perform system reset.

(9) After confirming that the electrical system is checked correctly, install the battery protection device, remove the protection facilities, close the engine compartment cover or luggage compartment cover, and return the car to the customer.