Where is the battery located in a car?

This blog will provide answers to the following questions: where is the battery located in a car? What are the different types of batteries used in a car? How to replace a battery in a car? Can you change the location of the battery in a car?

Where is the battery located in a car?

The main battery used for starting the engine and providing power supply to the car is located in the following places:

• The battery in the Engine compartment 
• Battery Under the seats
• Battery In the luggage compartment

All the places have come with benefits and drawbacks, car manufacturers also take the location of the starter motor and the alternator into account while determining the installation location of the main battery.

Let’s take a closer look at each of the locations in a car:

The battery in the Engine compartment

This is the most common location for installing the battery in a car. The engine compartment allows easy access to both terminals of the battery. In most cars, the battery is under the engine compartment panel secured by a lock in a battery tray or a box.

The jump post or the pre-fuse box can also be located close to the main battery and long cables are not required to connect the positive terminal of the battery to the jump post. The negative terminal consisting of a battery sensor is directly connected to the vehicle ground.

Installing the battery in the engine compartment also reduced the cost of the electrical wiring harness. The alternator, starter motor, and battery can be easily connected to each other with short wires. There is also less voltage drop-in as the length of the electrical wire is short.

The starter motor draws up to 250 amps from the main battery, therefore the distance between the starter motor and the battery should be less. The alternator is also connected to the same terminal as the starter battery. Therefore, when the alternator is generating the power it can easily charge the main battery with a minimum amount of voltage drop in the electrical line.

The main drawback of installing the battery in the engine compartment is the temperature. As the internal combustion engine operates at 80 degrees and the temperature of the exhaust gasses can surpass 400 degrees. So the engine compartment is a hot place despite the radiator fan and heat exchangers.

Constantly charging and discharging also increases the internal temperature of the battery, coupled with the hot surrounding temperature means the battery life is adversely affected.

Most of the batteries located in the engine compartment last for 2-3 years. After 3 years, the battery can develop cracks in the housing, or internal cells can be damaged due to high temperatures.

Battery Under the seats

This location is very common for sports utility vehicles and some old sedan cars. The sports utility or the SUVs have plenty of space under the floor of the passenger compartment. Therefore, instead of locating the battery in the engine compartment; car manufacturers prefer the under-the-seat location.

The battery can be located under the front or the rear seats, the positive electrical line is long as the starter motor and the jump post are in the engine compartment. There is no difference in the gauge of the wire; only the length changes depending on the location.

The capacities of the batteries that are located in the vehicle cabin are high. Batteries with high capacities can easily overcome the electrical line resistance and supply the current to the starter motor.

The removal and installation of the battery located under the seat are not easy. Some cars require the removal of the driver or the front passenger seat before the battery can be replaced. Performing a visual inspection and a battery test is also difficult as the space is restricted in the battery compartment.

The main benefit of installing the battery under the seat is the ambient temperature. The battery can stay at a cool ambient temperature as it is away from the internal combustion engine. Therefore, the battery life is also longer compared to the battery mounted in the engine compartment.

The battery in the luggage compartment

This location is used when the battery cannot be installed in the engine compartment. The engine compartment is very closely packed if the vehicle is powered by a V8 or V12 engine. There is no space to mount a battery in the engine compartment.

The problem with the battery in the luggage compartment is the length of the electrical line between the starter motor and the battery is very long. Also, a jump post or point in the engine compartment cannot be used since the battery is located in the trunk.

The battery life is good but it is susceptible to corrosion as the rubber seals in the trunk start to crack and water enters the luggage compartment. Replacing the battery is very easy and only requires the removal of luggage compartment panels. 

What are the different types of batteries used in a car?

The different types of batteries in a car are listed below:

• Lead acid batteries are flooded batteries and require periodic maintenance. Individual cells are submerged in the electrolyte. The concentration of the electrolyte can be checked from the maintenance caps on top of the battery housing.
• AGM batteries where AGM stands for absorbent gel mat, there is no liquid electrolyte in the battery housing, and the cells are surrounded by a gel mat containing the electrolyte. AGM batteries are maintenance-free batteries.
• Lithium-ion batteries are the most expensive batteries, they are made up of multiple individual cells. A battery management control unit is built into the battery to charge and monitor the cell voltage and temperature. Lithium-ion batteries are not used in cold countries because the battery does not have cold-cranking amps.

How to replace a battery in a car?

The procedure to replace a battery in a car is given below:

• Locate the position of the battery and remove the panel to gain access to both the terminals of the battery.
• Perform a visual check and look for any cracks in the battery housing, wear protective goggles and gloves.
• Unscrew and disconnect the negative terminal of the battery and place it on one side
• Unscrew and disconnect the positive terminal of the battery and place it on one side.
• Unscrew the bracket holding the battery in place and lift the battery carefully from the mounting plate.
• Install the new battery, and clean the terminals before tightening it.
• Always install the positive terminal first and then the negative terminal in order to prevent electrical short with the ground.
• Ensure the bracket and terminals are installed properly and torqued to the specification.

Conclusion

This blog explained the benefits and drawbacks of different locations of the battery in a car. The location of the battery can be changed as long as the voltage drop in the electrical line remains unchanged. The line resistance between the starter and the battery should not exceed 1 ohm.