Car batteries typically last between three and five years. After that, you're on borrowed time — and in the UK's cold winters, a weakened battery can fail without much warning. The good news is that most failing batteries do give signals before they give up entirely. Know what to look for and you can replace it on your schedule, not stranded in a car park.

At Tech & Tyres, we fit replacement batteries across Melksham, Trowbridge, Chippenham, Bath and across Wiltshire — usually the same day you call. Here are the five signs that your battery is on its way out.

Sign 1: Slow Engine Crank

This is often the first thing people notice. When you turn the key or press the start button, the engine turns over more slowly than usual — a laboured, sluggish sound rather than the immediate response you'd expect. In cold weather it may be even more pronounced.

A healthy battery delivers a fast, decisive crank. If yours sounds like it's struggling, the battery is losing capacity. It may start fine today. It might not start tomorrow — especially if temperatures drop overnight.

"The most common time for battery failures in Wiltshire is January and February — cold nights drain a weak battery faster than anything else. Don't wait until it fails completely."

Sign 2: Electrical Issues and Flickering Lights

A failing battery often struggles to power ancillary electrical components at their full capacity. Watch for:

  • Dimmer-than-usual headlights, particularly at low revs or when idling
  • Dashboard lights flickering when you start the engine
  • Slow electric windows or delayed response from powered seats
  • The radio resetting to default settings after the car is switched off
  • Power locks responding sluggishly

Modern cars have a large number of electrical systems drawing on the battery. When battery capacity drops, these are often the first things affected.

Sign 3: The Battery Warning Light

Your car's battery warning light (a red rectangle with a plus and minus sign) illuminates when the charging system isn't working properly. This could mean:

  • The battery itself is failing
  • The alternator is not charging the battery correctly
  • A faulty connection or corroded terminal

Don't ignore this light. If it comes on while you're driving, the car is running on battery alone — and when that runs out, the engine will stop. Have it checked promptly.

Sign 4: A Swollen Battery Case

If you can safely inspect the battery under the bonnet, look at its shape. A healthy battery has flat sides. A swollen or bloated case — where the sides have bowed outward — indicates the battery has been overcharged or exposed to excessive heat, causing internal gases to build up.

A swollen battery should be replaced immediately. It can leak or, in rare cases, present a risk of rupture. Don't attempt to use jumper cables on a swollen battery.

Sign 5: A Rotten Egg Smell

A sulphur or rotten egg smell around the engine bay can indicate a leaking battery. Lead-acid batteries contain sulphuric acid, and when a battery is overcharged or damaged, it can vent hydrogen sulphide gas. This smell is distinctive and unpleasant.

If you notice this smell, have the battery inspected immediately. A leaking battery can corrode nearby components and is a potential safety hazard.

Bonus: How Old Is Your Battery?

Even if you haven't noticed any of the above symptoms, age is a strong predictor of battery failure. Most standard car batteries last three to five years under normal use. If yours is approaching or beyond that age, proactive replacement before it fails is the smart move — it's far cheaper than a recovery call-out.

You can usually find the battery manufacture date stamped on the casing, or check your service records.

Think Your Battery Is Failing?

We test and replace car batteries across Melksham and Wiltshire — same day in most cases. We come to you, test the battery on the spot, and replace it there and then if needed.

Call 07837 637217

What To Do If Your Battery Fails

If your battery has already failed and you can't start the car, you have a few options:

  1. Jump start: If you have jump leads and a willing helper, a jump start can get you going temporarily. Drive for at least 30 minutes to allow the alternator to partially recharge the battery. Don't switch off until you're somewhere you can get help.
  2. Call Tech & Tyres: We can come to you — at home, at work, or at the roadside — test the battery, and fit a replacement on the spot. For many drivers across Wiltshire this is quicker and less stressful than calling a breakdown service.

Call us on 07837 637217 and we'll confirm availability and give you a price straight away. Or send us an enquiry if it's not urgent.

For more information on our battery service, see our Battery Replacement page.