Introduction
While Australia is known for its heat, many regions experience cold winters that challenge car batteries. From the Snowy Mountains to Tasmania, from highland Victoria to the tablelands of New South Wales and Queensland, cold weather creates unique demands on your vehicle's battery.
Understanding how cold affects batteries and taking appropriate precautions can prevent the frustration of cold-morning failures and extend your battery's service life.
How Cold Affects Batteries
Cold weather impacts batteries in several ways:
Reduced Chemical Activity
Battery chemistry is temperature-dependent. As temperatures drop, the chemical reactions that produce electricity slow down significantly:
This means your battery has less power available precisely when your engine needs more power to start.
Increased Engine Demand
Cold weather simultaneously increases the power needed for starting:
The Compounding Effect
This creates a challenging situation: your battery can deliver less power while your engine demands more. A battery that starts your car easily at 25°C might struggle or fail at 5°C.
Preparing Your Battery for Winter
Taking steps before cold weather arrives prevents cold-morning failures:
Get Your Battery Tested
Before winter, have your battery load-tested at an auto parts store or auto electrician. This test reveals how much capacity your battery has lost and whether it can handle cold-weather demands.
A battery that tests as "marginal" in autumn will likely fail on the coldest winter mornings. Replace it before you get stranded.
Clean and Inspect
Corrosion on terminals increases electrical resistance, making starting even harder. Before winter:
Check the Charging System
Your alternator keeps your battery charged. A weakening alternator may maintain the battery adequately in summer but fall short in winter when cold starting draws more power.
Have the charging system tested along with the battery. Ensure the alternator is producing 13.5-14.5 volts when the engine is running.
Ensure Full Charge
A fully charged battery resists freezing and delivers maximum power. A discharged battery:
If your battery is undercharged, either take a long drive or use a battery charger to bring it to full charge before cold weather sets in.
Cold-Weather Starting Tips
When cold mornings arrive, these practices help achieve reliable starts:
Minimise Electrical Load
Before turning the key:
This lets all available battery power go to the starter.
Proper Starting Technique
If the Engine Turns Slowly
Slow cranking indicates the battery is struggling. If the engine doesn't start:
Consider a Block Heater
For vehicles in consistently cold areas (alpine regions, Tasmania), an engine block heater can dramatically ease cold starting. These devices warm the engine overnight, reducing starting demands.
Winter Maintenance
Ongoing attention during winter helps maintain battery health:
Regular Driving
Short trips don't allow the battery to fully recharge. In winter, when starting draws more power, this can lead to progressive undercharging.
Aim for at least one 30+ minute drive per week to allow the battery to fully recharge. Highway driving is better than city driving for recharging.
Keep the Battery Warm
While you can't control the weather, you can take steps to reduce battery cooling:
Monitor Voltage
If you have a voltmeter or multimeter, check your battery voltage occasionally:
Jump Starting in Cold Weather
Cold-weather jump starting requires extra care:
Before Jump Starting
Allow the donor vehicle to run for several minutes with its engine at slightly elevated RPM. This warms the donor battery and provides maximum charging power.
The Process
Follow standard jump-starting procedures:
After the Jump
Let the vehicle run for at least 20-30 minutes before shutting it off. A short trip won't fully recharge the battery, and you may not be able to restart.
Consider driving to an auto parts store and having the battery tested. A battery that needed a jump in cold weather is likely weak and may fail again.
When to Replace
Certain signs suggest replacement regardless of season:
Age Factor
Batteries over 4-5 years old are more likely to fail in cold weather. If your battery is approaching this age, preemptive replacement before winter is wise.
Marginal Test Results
If testing shows your battery is "weak" or "marginal," replace it. A battery that barely passes testing will likely fail when cold weather arrives.
Previous Cold-Weather Problems
If your battery struggled last winter, don't expect it to improve. Battery capacity only decreases with age and use.
After Deep Discharge
A battery that has been completely flattened in cold weather may have suffered permanent damage. Even if it accepts a charge, have it tested before relying on it.
Choosing a Cold-Weather Battery
If you're replacing your battery, consider these factors for cold-climate performance:
Higher CCA
Look for a battery with CCA exceeding your manufacturer's minimum specification. The extra starting power provides a margin for cold conditions.
Quality Construction
Premium batteries from reputable manufacturers typically perform better in temperature extremes. The price difference is usually justified by improved reliability.
Fresh Manufacturing Date
Battery capacity declines from manufacture. Check the date code and choose the freshest battery available.
AGM Technology
AGM batteries perform better than flooded batteries in cold conditions because:
Conclusion
Cold weather challenges batteries, but proper preparation and maintenance can prevent cold-morning failures. Get your battery tested before winter, ensure it's fully charged and cleanly connected, and consider replacement if test results are marginal.
By understanding how cold affects batteries and taking appropriate precautions, you can rely on your vehicle throughout winter without the frustration of failed starts.