Car Batteries in Adelaide Heat: What Summer Does to Them

This guide is for Adelaide drivers who want their car to start on the first try, every time, through a South Australian summer and the cooler months after it. It explains what heat does inside a battery, why the northern suburbs can be harder on batteries than the city, and what you can check, choose and change to get more life out of yours.

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How hot Adelaide gets

Adelaide's heat is not just a feeling. On 24 January 2019, the Bureau of Meteorology recorded 46.6°C at Adelaide (West Terrace / ngayirdapira), beating the site's previous record of 46.1°C set on 12 January 1939. On the same day Kent Town and Parafield Airport both reached 47.7°C, and Edinburgh RAAF reached 47.5°C. You can read the details in the Bureau's 2019 climate summary for Greater Adelaide.

Nights can stay hot too. On 20 December 2019, Edinburgh RAAF recorded a minimum of 34.2°C, and West Terrace's overnight low was 33.6°C, the highest minimum in that station's record. When the night doesn't cool down, nothing under your bonnet gets a break either.

What heat does inside a battery

A lead-acid car battery makes power through a chemical reaction between lead plates and an acid electrolyte. Heat speeds that reaction up. That sounds helpful, and on a hot morning a tired battery may even crank better than it would in winter. But the same heat also speeds up the slow damage that ends every battery's life: the positive plates corrode faster, water is lost from the electrolyte, and the battery discharges itself faster while the car is parked.

The engine bay makes things worse. Under the bonnet, the battery sits next to a hot engine, a radiator and an exhaust manifold, so it runs well above the air temperature on a summer afternoon. A car that sits in an open car park at Marion or Elizabeth on a 40°C day, then drives home in peak hour, cooks its battery from both outside and inside.

Why batteries often fail after the heat, not during it

A common pattern is a battery that seems fine all summer, then fails on the first cool morning in autumn or winter. The damage was done in the heat. The plates lost capacity over the hot months, but warm weather hid it because a warm battery delivers its power easily. When the temperature drops, the battery's chemistry slows down, the engine oil is thicker, and the starter needs more current. A battery with lost capacity can't keep up, and the engine cranks slowly or not at all.

So the best time to test a battery in Adelaide is at the end of summer, before the cool mornings arrive. A load test or a conductance test will show a weak battery before it leaves you stranded. Our guide on how to test a car battery explains the options, and it's worth doing even if the car seems to start fine.

The north is often hotter than the city

The 2019 record day shows something Adelaide drivers in the north already know. The inland stations at Parafield Airport and Edinburgh RAAF recorded higher maximums than West Terrace in the city. If you live or work around Salisbury, Elizabeth or Edinburgh, expect your battery to have a harder life than one in a car garaged near the coast at Glenelg.

That doesn't mean a battery won't last in the northern suburbs. It means shade, good charging and regular checks matter more there.

Simple ways to protect your battery from the heat

You can't change the weather, but you can change how much of it your battery soaks up.

• Park in shade or under a carport when you can. A garage or carport at home makes the biggest difference because the car spends most of its life there.
• Keep the battery's heat shield or cover in place. Many cars come with one, and it's often left off after a battery change.
• Keep the terminals clean and tight. Heat and vibration loosen poor connections, and corrosion adds resistance. See how to clean corroded battery terminals.
• Check the hold-down clamp. A loose battery vibrates, which damages the plates inside.
• If you have a serviceable battery with removable caps, check the electrolyte level more often in summer and top up with distilled water only.
• If the car will sit for weeks, such as while you're away over the Christmas break, use a quality smart charger or battery maintainer.

Choosing a battery for Adelaide conditions

Always start with the type and size your car's maker specifies. Many newer cars have stop-start systems that need an Enhanced Flooded Battery (EFB) or an Absorbent Glass Mat (AGM) battery. Fitting a cheaper standard battery to these cars usually shortens its life and can upset the stop-start system. Some cars also need the new battery registered with the car's computer after fitting. Our guide to car battery types explains the differences.

Look at the battery's date code when you buy. A battery that has sat on a shelf for a long time in a hot warehouse has already used some of its life. And remember that a battery's cold cranking amps rating matters in winter, even in Adelaide, because that's when a heat-weakened battery shows its age.

When it's not the battery

Heat also stresses the charging system. Alternators work hard in summer because the air conditioning fan, radiator fans and blower all draw current, often in slow traffic where the alternator spins slowly. A failing alternator or a corroded earth strap can leave a good battery undercharged, which looks like a bad battery.

If you've replaced a battery and it goes flat again, have the charging system and any parasitic drain checked before buying another one. Auto electricians in the Northern Suburbs, the Southern Suburbs and the eastern suburbs can test the battery, alternator and wiring together.

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Questions Adelaide drivers ask

How long does a car battery last in Adelaide?

It depends on the battery type, the car, how it's driven and where it's parked, so there's no single answer. Heat is one of the main things that shortens battery life, which is why batteries in hot climates generally don't last as long as in cool ones. Testing your battery at the end of each summer is the best way to know where yours stands.

Why did my battery die on a cold morning after a hot summer?

Summer heat speeds up plate corrosion and water loss, so the battery loses capacity over the hot months. Warm weather hides that loss because a warm battery delivers power easily. On the first cold morning, the battery's chemistry slows down and the engine needs more current to crank, so the weakened battery can no longer start the car.

Can I put a normal battery in a car with stop-start?

Generally no. Stop-start cars are designed for EFB or AGM batteries, which handle frequent restarts and deep cycling. A standard flooded battery will usually wear out quickly in these cars and may cause the stop-start system to stop working. Check your owner's manual or the old battery's label, and fit the type the maker specifies.

Does parking in the shade really help my battery?

Yes. The battery sits in the engine bay, which gets much hotter than the air on a sunny day. Parking in shade, under a carport or in a garage keeps the whole car cooler, which slows the corrosion and water loss that wear a battery out. It matters most where the car spends the most hours, which is usually at home or at work.

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