Why UK Heatwaves Can Accelerate Car Battery Ageing
With summer quickly approaching and temperatures rising, cars and car batteries will also experience a rise in temperature. Whether static or moving, the core temperature of batteries increases as temperature increases which, if left untreated, can accelerate battery ageing.
If the temperature is hot outside, you can guarantee that it’s hotter under the bonnet. Even 22 °C ambient can accelerate battery ageing.
This guide explains the causes of battery ageing and how motorists can implement small adjustments that will elongate their battery life and care for its health.
How Summer Heat Drives Battery Chemistry & Ageing
Heat waves can affect car battery life for three main reasons:
- Heat speeds up chemical reactions inside the battery.
- Heat causes the battery’s electrolyte (a mixture of acid and water) to evaporate faster which reduces the fluid level and exposes internal components to air.
- High temperatures accelerate the formation of lead sulfate crystals which contribute to internal corrosion.
Whilst it might only be 22 °C ambient on a sunny day, your car battery will be experiencing 40 °C – 50 °C. This under-bonnet spike can damage your battery, lead to the premature ageing of the battery and ultimately may result in your battery dying.
What are the Symptoms of Heat-Stressed Batteries
Signs Your Battery Is Ageing
- Engine takes longer to start
- Dim headlights
- Issues with electrical components such as windows and locks
- Swollen battery case
- Frequent jump starts
- Dashboard warning light
Heat impacts battery health more severely than you would expect. In fact, for every +8 °C above 25 °C, the life of a lead-acid battery is halved. With under-bonnet temperatures higher than ambient temperatures, it is far easier for the battery to achieve that fatal +8 °C.
Conversely, extreme cold can be just as devastating to a battery’s lifespan as extreme heat. When temperatures plunge, the electrolyte thickens and ion mobility slows dramatically, causing internal resistance to skyrocket and available capacity to plummet. For more detailed tips on preparing your vehicle and its battery for the cold, check out BBL Batteries’ winter guide: Is Your Vehicle Ready for Winter?
Q&A
- Why is my car battery weak when it’s hot?
The electrolyte level (a mixture of acid and water) in a battery slowly evaporates when it heats up. When this level gets too low, the internal plates of the battery are not protected and damage can occur. This damage results in the battery producing less voltage which causes a lower power production, and therefore a weak battery.
- Does heat cause my battery to fail?
Yes, heat can cause battery failure due to damage of internal components.
- How does temperature affect battery voltage?
Low temperatures slow down the chemical reactions in a battery reducing the battery’s ability to deliver current and leading to lower voltage readings.
High temperatures accelerate these reactions, increasing current output and leading to higher voltage readings. Both extremes cause the acceleration of battery degradation.
- Is a car battery heat shield necessary?
No, they are not necessary. However, they are an effective preventative measure to slow battery ageing.
A car battery heat shield acts as a barrier around the battery. It protects the battery from heat generated by the engine and exhaust system.
- How do I know if my battery or alternator is at fault?
Battery fault symptoms include: Car not starting, clicking sound, and jump start helping once but not again.
Alternator fault symptoms include: Battery warning light, dim interior and/or exterior lights, stalling after a jump start, and electrical components not working properly.
- Why do batteries self-discharge in hot weather?
High temperatures accelerate the chemical reactions inside a battery which causes faster evaporation of the electrolyte and increased internal corrosion. This causes premature ageing and can cause your battery to fail unexpectedly.
Preventative Steps & AGM/EFB Upgrades
Simple Heat-Protection Measures
- Park in the shade whenever possible
- Keep terminals clean and corrosion-free
- Check electrolyte levels (for serviceable batteries) and top up with distilled water
- Avoid high-draw accessories (air-con, heaters) while idling
Heat Shields & Insulation
- Fit a bespoke under-bonnet heat shield to deflect engine and exhaust heat
- Use insulating mats designed for automotive batteries
Upgrade to AGM or EFB
As we start to regularly face fluctuations in temperature, and you don’t already drive a start-stop/high-draw vehicle, consider switching to:
AGM Batteries: Lower self-discharge, greater resilience in hot (and cold) climates.
- Recommended: 115AGM Avon Battery | 096AGM Avon Battery
EFB Batteries: Cost-effective, durable option for standard vehicles.
- Recommended: 096EFB Avon Battery | 115EFB Avon Battery
Free BBL Batteries Health Check
Don’t let under-bonnet heat shorten your battery’s life. Pop into your nearest BBL Batteries branch today for a free in-store Battery Health Check, and we’ll advise whether simple maintenance or an AGM/EFB upgrade is the best way to keep you powered through the summer.
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