Understand the role and importance that a battery plays in the car

Understand the role and importance that a battery plays in the car />


Batteries are an integral part of cars. BatteryPower Zone (BPZ) believes that every car owner should understand the role and importance that a battery plays in the car. We know that our customers want to make the right decision at the time of purchasing a battery so this information is here to help.

Automotive batteries are often referred to as SLI or Starting, Lighting and Ignition batteries given their role in feeding the starter when the ignition key is turned on. A SLI battery’s primary role in a vehicle is to supply power to the starter motor to start the vehicle.  This is known as CCA – cold cranking amps.  This rating is calculated at -18°C and is calculated as the amount of amps the battery can supply the starter motor continuously for 30 seconds to a minimum voltage of 7.5 Volts (See battery label for this specification). 

Most people are under the misapprehension that the battery’s role is also to supply power to the vehicles electronic system. This in fact is the primary role of the vehicle’s alternator.  The battery may supply emergency power to the electronic system:

  1. When the alternator is not charging (Refer to the reserve capacity (RC*) on the battery for further information)
  2. For short periods of time when the ignition is switched off.

* RC – Reserve Capacity is defined as the amount of usable electrical power the battery can supply the electronic load on a vehicle should the alternator fail.  The average load is calculated at 25 Amps and the Reserve Capacity is the amount of time in minutes that the battery will supply a load of 25 Amps to a minimum voltage of 10.5 Volts.

There are a few common types of batteries you can find in a car. For a broader discussion, we would include electric cars as well where the battery provides the motive power instead of the SLI functionality you would find in fuel-based cars.

These include:

  • Wet/Flooded – These may be presented in a vented or “top up” version, or as a sealed version. This is the more common lead-acid battery that you would find in most cars. They are highly popular in cars due to their affordable price.

  • Calcium-Calcium – The addition of Calcium in both Positive and Negative plates is a distinct advantage in enhancing battery performance and eliminating dangerous gassing.  Some manufacturers only include calcium in the positive plate. 

  • EFB – Enhanced Flooded Battery is a step up from normal wet acid batteries, and a step down from AGM (Absorbed Glass Mat) batteries.  These batteries have enhanced performance characteristics and are used extensively in start stop vehicles.

  • VRLA - Valve Regulated Lead Acid battery.
    • AGM – Absorbed Glass Mat may be used in SLI applications for vehicles with high electrical demands and with adjusted technology may also be used in stationary applications. Bear in mind that AGM refers to the state of the battery’s electrolyte and is not indicative of the performance characteristics of the battery.  AGM Batteries (with differently designed plates) may be used in SLI, Float, High heat, Deep Cycle applications.

NOTE: It is not advisable to use a SLI AGM battery in a Deep Cycle application. Although a SLI AGM battery will perform better than a normal wet acid battery.  See catalogue for battery applications.

  • GEL – Gel Batteries are not designed for SLI applications. They are designed for stationary applications with strict reference to charging voltage and ambient temperature.

  • Deep cycle – They are suitable for providing motive power and stationary backup power rather than a starting function. This is why they are used, EG: in electric cars, golf carts, UPS, and Marine and Leisure applications. They are capable of providing steady power over a long period of time. Some Deep Cycle batteries are designed to function in a dual role of both SLI as well as supplying auxiliary power. Deep cycle batteries are relatively more expensive.

At BatteryPower Zone (BPZ) we stock and sell a wide range of automotive batteries and our dedicated team of battery specialists is on hand to assist with your automotive battery requirements.