What is a Car Battery and Its Role in a 12V Electrical System
A car battery is the heart of a vehicle’s electrical system, playing a critical role in powering all the main essential electrical functions of the car.
In a 12V electrical system, the battery provides the initial energy needed to power the starter motor and start the engine, and serves to power accessories including lighting, infotainment, and other onboard electronics when the vehicle is off.
Remember however, a Battery on its own is not responsible for generating the electricity to power these systems, but acts as a storage unit to capture that energy created by the vehicles charging system.
The Basics of a 12V Electrical System
The vehicles main cranking battery is charged by the alternator, which is driven by a belt connected to an engines crankshaft.
Most vehicles, including 4x4s, use a 12V electrical system. This voltage standard is responsible for ensuring consistent and stable power distribution to various systems in the vehicle. The car's battery is responsible for supplying this 12V power, especially when the engine is not running. Once the engine starts, the alternator takes over and recharges the battery while distributing power to the rest of the car.
The Role of the Battery
A vehicles main cranking battery serves three major functions:
Starting the Engine: When you turn the key or press the ignition button, the battery sends a high burst of energy to the starter motor, which in turn starts the engine.
Powering Accessories: While the engine is off, the battery powers essential systems like lights, the radio, the car’s computer, and other 12V accessories. This is particularly important for off-road vehicles, where additional electrical components like winches, auxiliary lights, and fridges are often used.
Storing Generated Electricity: The battery serves as a means to store the electricity generated by the vehicles charging system. This consists of an alternator drives by the engine to produce current, replacing the energy used to start the battery and power the vehicles various electrical systems. Without a charging system to replace the energy used by the vehicles various starting and accessory systems, a vehicles cranking battery would very soon go flat!
A simple diagram showing the vehicles charging, cranking and main accessory system.
The Battery is responsible for the storage of power, provided from the vehicles alternator, providing way to provide large burst of power to power the starter motor and start the engine.
Battery Maintenance in a 12V Electrical System
The performance of your vehicle's 12V electrical system is only as good as the battery's health. Regularly check for corrosion, ensuring proper charging with systems like a dual battery setup, and monitoring power output are critical for keeping the 12V electrical system running smoothly. Check for parasitic drains - which are small electrical drains due to accessories being left on, or issues with wiring - and fix them quickly!
While many batteries are full sealed nowadays, there are still some that allow access to the filler holes for each cell. Check the health of each cell using a hydrometer and keep the battery topped up using demineralized water
Drop Bear 4x4 Tip: To extend the life of your batteries, periodic charging on a stand alone battery charger every 2 - 4 weeks will ensure your car batteries run in top shape at all times! Remember, a 5 minute drive down to the servo doesn’t cut it!
This helps offset the discharge built up over time due to a car sitting around, powering accessories, like the radio, when the vehicle is off, the insufficient charging of the battery from the alternator due to short drives.
Deep Cycle Batteries: Purpose and Construction
Unlike traditional starter batteries, deep cycle batteries are designed for sustained energy use rather than short bursts of high power. This makes them ideal for powering accessories when the engine is off, particularly in dual battery setups for off-road and camping scenarios.
Construction Differences:
Thicker Plates: Deep cycle batteries have thicker internal plates that allow them to discharge more deeply without damage. This makes them more robust for long-term energy use, whereas standard batteries are built to deliver short bursts of energy for starting the engine.
Higher Discharge Capacity: Deep cycle batteries are designed to discharge to a much lower capacity and then recharge repeatedly, providing long-term, stable power for accessories like fridges and lights.
why cant i use a normal car battery for deep cycle use?
Using a car’s cranking battery for deep cycle applications is a bad idea due to significant differences in their internal construction and purpose. Cranking batteries are designed to provide short, high-power bursts to start your engine.
Deep cycle batteries, on the other hand, are made to provide a steady supply of energy over extended periods. If you use a cranking battery as a deep cycle one, you’ll drastically reduce its lifespan and performance.
Over time, repeated deep discharges can cause internal damage, lead to poor performance, or even result in swelling and bulging of the battery casing—signs that the battery is nearing failure. For off-roading and camping setups where you're powering accessories like fridges or lights for long periods, always opt for a purpose-built deep cycle battery.
Need a battery that can do it both? Dont fret!
Nowdays, manufacturers like Century Batteries and Optima offer batteries that can do both!
Their unique construction allows them to perform double duty, powering 12v accessories while providing outstanding cranking performance. Just remember to keep them charged!!
The Importance of Deep Cycle Batteries in 4x4s
In a 4x4 setup, especially for those venturing into remote areas, deep cycle batteries ensure you have power when needed without draining the starter battery.
This means your vehicle can still start after a night of powering camping gear or other 12V accessories. Whether using AGM, Gel, or Lithium deep cycle batteries, each has its benefits in terms of lifespan, performance, cost and weight.
Want to learn more about 12v dual battery systems?
Keen to learn more about the ins & out of 12v dual battery systems? Check out our blog post on understanding 12v dual battery setups here
You can also learn more by reading Century batters Expert Advice Section!
