What is a car battery and what does it do?

A car battery is a device that powers the electrical components of the vehicle. It plays a crucial role in starting your vehicle, ensuring that the lights work, the wipers wipe, the music plays, and many other functionalities. In the simplest description, without it, a car won’t start.

On account of the increased production of EVs in recent times, batteries are now integral units. They store the electric power needed to run the car. With the rechargeable nature of batteries, it’s now possible to use them over and over again for a long time. 

Today, cars come with different types of batteries. Not sure what kind of car battery is in your vehicle? Worry not. In this guide, we take a look at the various types to help you identify the kind of battery fitted in your car.  

How do car batteries work?

When the ignition key is turned (or pressed, in the case of an ignition button), the action prompts the battery to release the stored electrical energy. This electrical power is channelled fast to the starter, which then cranks the engine up.

The extra power is then channelled to electrical components, powering them in the process. The alternator enables the charging and discharging of the battery. If the battery level is too low, your car will have problems. In this case, you may need to jumpstart or replace the battery.

Types of Car Batteries

Automakers fit different batteries in their units. Each of these batteries has a unique technology and mode of operation. 

1. Wet Cell Batteries

Otherwise known as flooded batteries, these are standard lead-acid units that have been in use for a while now. 

Lead-Acid Wet Cell

The lead-acid wet cell is the oldest and most prevalent car battery type in the market. As the name suggests, they contain an electrolyte. This electrolyte consists of water and sulphuric acid. 

They have positive and negative terminals where the electrodes dipped in the electrolyte connect. It is the chemical reaction between the electrode and electrolytes that generates a charge, which is then stored.

The caps at the top make it easy to identify one. During their lifespan, they need to be topped up with distilled water through the openings sealed by the cap. 

Lead-Acid wet cells are almost always labelled, so spotting one is not that difficult. They are the cheapest units and have a short life cycle. They require regular maintenance (topping up with battery water).

Wet cell batteries are of three main types as described below.

i. SLI (Starting, Lighting, Ignition)

SLI batteries represent the typical batteries used in vehicles. They produce instant power bursts excellent for starting, lighting, and ignition. As the engine picks up speed, the alternator takes over the role of powering the components of the car.

This type powers up the headlights and rear lights. It is good practice to always check that your SLI battery is functioning. You don’t want to discover it malfunctioning when it’s too late, such as when you’re driving on an unlit road at night.

SLIs are usually in a continuous cycle of charge and discharge since they have a very small charge cycle.

ii. Deep-Cycle Batteries

Unlike SLI batteries, deep cycle batteries produce sustained power for more extended periods. One can draw power from them until they are completely run down, after which they’re recharged, hence the name deep cycle.

Due to this characteristic, they can power a car’s electrical systems and components even when the engine is not running. On the downside, they can’t deliver big surges of power to start large engines.

Manufacturers recommend that this type of battery should not be allowed to go completely empty. Deep cycle batteries should be recharged while there’s still at least 20% of charge in them.

iii. Dual Purpose

Dual-purpose batteries are a hybrid of SLIs and Deep Cycle batteries. They have both starting and component-driving capabilities. Typically, these units cost more than the usual SLIs.

You are probably wondering why they aren’t widely used. Well, while dual-purpose batteries boast of double functions, they are not exceptional at either of these functions.

All cars come with an alternator under the hood. The alternator powers the audio system, GPS, and other functions, thereby eliminating the need for Deep Cycle batteries.

Even when the vehicle is stationary, the battery usually has enough charge to keep the systems running for some time. However, if you need to draw juice out of the battery for a long time, a dual-purpose battery is ideal.

2. Valve-Regulated Lead-Acid (VRLA) Batteries

VLRA batteries are entirely sealed and can’t be serviced. They are considered the safest lead-acid batteries hence can be installed in closed spaces. They require only little maintenance. 

They need to be replaced when spoilt but are designed to last longer than other battery types.

The most common types of VRLAs are Absorption Glass Mat (AGM) and Gel Cell Batteries. Though they are maintenance-free, regular cleaning and testing is necessary.

Lead-Acid Gel Cell (or Dry Cell)

The electrolyte used in these batteries is usually in gel form. They are wholly sealed, eliminating the need for ventilating gases. Most of them look similar to wet-cell batteries except for the flat tops and the absence of caps.

If you shake both dry-cell (gel-cell) and wet-cell units, you can feel some movement in the latter after you’ve stopped shaking. 

Absorbed Glass Mat (AGM)

AGM batteries are similar to gel-filled ones in that they, too, are completely sealed. They don't require topping off. Absorbed Glass Mat batteries use a mesh of glass fibre where the electrolyte is held hence the name.

They don't have extra movement after you've stopped shaking them. Except for the labelling, telling apart an AGM battery from a gel-filled one is hard. They are lighter and can be installed in closed spaces at unusual angles.

Even when they are not in use, AGMs can hold a charge for more extended periods. They have a slow degrade rate, which translates in a longer lifespan. To that end, they are also costly.

Lithium-ion Batteries

Li-ion batteries are mostly used in hybrids and EVs. They are incompatible with most cars on the road, but they are the future. These batteries store insanely large amounts of power compared to any other types of batteries. 

What’s more, they are relatively smaller and lighter. Mini-versions of Li-ion batteries have an application in portable electronic devices such as phones and laptops.

Sadly, they have a short life span of about three years, after which they need replacement. As a safety precaution, the charging of Li-ion batteries should be closely monitored to avoid overcharging.

Wrap Up

Car batteries come in different sizes depending on the model that you own. Most sizes fit a specific line of cars by the same automaker. The position of your car battery also varies depending on the car’s make. 

Hopefully, with this guide, you now have a working idea on how to identify the type of the battery unit that’s in your car. For similar guides, please refer to the blog section of Carpart.com.au.