If you test your battery and find that it is not working as it should, you will need to replace it. It's not as big of a job as it sounds, and it's certainly possible to do it yourself if you're very careful. Defective batteries can be very dangerous for a number of different reasons. The acid inside them is extremely corrosive, and in the event of any leakage, it can cause great damage.
Electricity itself is very powerful, and if you connect the wrong wires to the wrong connection points, you could seriously injure yourself or seriously damage your vehicle. Also, the battery in a Mercedes ML / GL, unlike other cars, is located in a rather unusual place - under the passenger seat, and as a rule, without partial removal of the seat, it is impossible to change it.
How to replace a car battery?
First, make sure you park on a level surface with enough room for full access to the hood and engine. Some cars automatically lock the doors when you start changing the battery (the electrical system disables the central locking), so keep the keys outside the car. Put on safety goggles and thick gloves. Battery acid is highly corrosive and can cause permanent damage if it comes into contact with eyes or skin.
Before disconnecting anything, make sure you have all the security codes for your vehicle's electrical components. Radios, navigators, etc. You may be asked to enter a code after changing the battery and you will not be able to use any of these features until you enter the correct number. Before replacing a battery, it's a good idea to read your vehicle's owner's manual to know what settings will need to be reset after a new battery is installed.
Open the cover and secure it in place
Find the battery. Most of them are near the engine, but in some makes and models of cars, they can be found in the trunk or under one of the seats. If it is difficult to distinguish between the wires connecting the battery, then you must label them positive and negative before disconnecting them. Replacing the vehicle's wiring in the wrong order can cause serious damage to the electrical system. Disconnect the negative cable, making sure that the clip does not come into contact with metal parts of the engine. Do the same for the positive cable.
Batteries are installed differently in different vehicles. Remove any clips or screws that hold the battery in place, remembering to hold any parts you remove in case the new battery doesn't come with new clips or screws.
Carefully remove the battery from the vehicle. Keep in mind, batteries are quite heavy, so you may need an extra pair of hands. Prepare a new battery. Double check that the battery you are about to install is the correct model for the car. Screw or secure the battery in place.