Car batteries rarely quit without warning. Most give you a few clues first, and catching them means you replace the battery on your schedule instead of in a parking lot. Here’s what to watch for.

The 7 Warning Signs

• Slow cranking. The engine turns over sluggishly before it starts, especially on cold mornings.
• Clicking when you turn the key. A click with no crank usually means the battery is too weak, or a cable is loose or corroded.
• Dim headlights. They look weak at idle and brighten when you rev the engine.
• A battery or charging light on the dashboard. That light can also point to the alternator, so have both checked.
• Electrical glitches. Slow power windows, a radio or clock that keeps resetting, or a flickering dash.
• Needing jump-starts. One jump can happen to anyone. Needing them often means the battery isn’t holding a charge.
• A swollen case or a rotten-egg smell. The battery is damaged. Don’t jump it or charge it. Keep sparks and flames away and have it replaced.

Check Its Age

Most car batteries last about three to five years. Heat is harder on them than cold, so batteries in hot climates often wear out sooner. The date is usually on a sticker or stamped on the case. Once a battery is past three years old, have it tested every year.

Test It Before You Buy

With the engine off, a fully charged battery reads about 12.6 volts on a multimeter. A reading near 12.2 means it’s only about half charged. Voltage doesn’t tell the whole story, though: a battery can show a full charge and still be failing inside. A load test tells you for sure, and many auto parts stores will do one free.

Rule Out the Easy Fixes

Look at the terminals. White or green crust, or a cable clamp you can twist by hand, can make a good battery act dead. Clean the terminals and tighten the clamps, then see if the problem goes away. If the battery tests good and still keeps dying, the alternator or something draining power while the car is parked may be the real cause.

My guide walks you through replacing a car battery, step by step.

Get the full guide: How to Replace a Car Battery by Hank Palmer, on Amazon