How to Tell If Your Car Battery Is Bad: 8 Common Signs

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Can you drive with a weak car battery? Our experts weigh in

Co-authored by Duston Maynes and Amber Crain

Last Updated: April 5, 2024 Fact Checked

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Weak Battery Symptoms

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What To Do

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Weak Battery vs. Bad Alternator

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Causes

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Can I drive with a weak battery?

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Video

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Expert Interview

If you suspect your battery might be going bad, you're in the right place. We spoke to two automotive repair specialists about the earliest signs of a weak car battery, which include dim headlights, malfunctioning electrical components, and a slow-starting engine. In this article, we'll go through the full list of signs to look for to diagnose the issue. We'll also talk about what causes a weak car battery and how to tell the symptoms of a bad alternator from battery issues. Read on to learn more!

Signs of a Bad Battery

Dim headlights, malfunctioning electrical components, and a slow-starting engine are some of the earliest signs of a weak car battery.
Pop the hood and inspect the battery for additional symptoms like corrosion on the terminals or a swollen or damaged battery case.
A bad alternator shares similar symptoms with a weak battery, but one tell-tale difference is that a bad alternator also causes rattling and grinding sounds.

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Section 1 of 5:

Weak Battery Symptoms

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1
Dim headlights Headlights (and your car’s other electrical components) are powered directly by the battery. Sudden electrical issues, like dim or flickering headlights, are early signs that your vehicle’s battery is getting weak.^{[1]
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Research source} You may notice other electrical issues like:
- Dashboard controls and interior lights falter or stop working
- Power windows (and sunroof) stop working
- Devices won’t charge when you plug them into the port
If you turn the key in the ignition and the engine’s startup is noticeably sluggish, you’re definitely dealing with a weak battery issue.^{[2]
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Research source} It might take several times for the engine to finally crank up, or your vehicle might make a low “rurrr rurrrr rurrr” sound and never turn over at all.

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If you try to crank your engine and nothing happens, or if you hear a clicking sound but the engine never turns over, it means your battery is already dead or incredibly weak. To get on the road again, change the battery yourself or jumpstart the car so you can get it to a mechanic.^{[3]
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Battery terminal corrosion Pop the hood and examine the battery's terminals (the positive and negative caps where it connects to your car). If you see a lot of blue-green powder or a crystal-like substance, you may need a new battery. A little bit of residue can usually be cleaned off, but a lot of corrosion means the battery is leaking acid and needs to be replaced as soon as possible.^{[4]
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- Wear protective gloves and safety glasses when you’re dealing with battery corrosion. Automotive repair specialist Duston Maynes says, “the residue is battery acid and it can burn your skin. You can clean off the corrosion, but this is generally a sign that your car needs a new battery.”
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Swollen battery case While you have the hood popped, inspect the battery’s exterior casing. If you see any signs of swelling, cracking, or bulging, it means the battery is damaged and weakening, and it needs to be replaced as soon as possible.^{[5]
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- Keep in mind that a car battery is typically a rectangular shape; if the rectangle looks irregular at all, there’s definitely a battery issue that needs attention.
Leaking battery acid smells distinctly of sulfur. If you smell that infamous rotten egg smell when you’re near your vehicle, the battery is leaking and getting weak. It needs to be replaced fairly quickly so the acid doesn’t drip and corrode other parts of your engine.^{[6]
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If you’ve recently been relying on jumpstarts to get your vehicle on the road, the battery is low and probably can’t hold a charge anymore–it needs to be replaced. This is especially true if the battery is more than 3 years old.^{[7]
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If the battery light on your dashboard lights up, there’s something going on with your car’s electrical system, and one potential culprit is a weak or dying battery. If you see this light along with any of the above-mentioned symptoms, your battery may need to be replaced.^{[8]
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Section 2 of 5:

What to Do if You Have a Weak Car Battery

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Replace the old battery with a new one ASAP or see a mechanic. If your vehicle's battery is weak, it's important to get a new battery as soon as you can to avoid issues like getting stranded somewhere or experiencing malfunctions you aren't prepared for. Plus, driving your car around with a weak battery can cause other mechanical issues and damage to your car.^{[9]
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- If you want to replace the battery yourself, go to an auto parts store and buy a battery that's appropriate for the year, make, model, and engine size of your vehicle. Typically, a new battery will cost $45 to $250.^{[10]
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- If you'd prefer a professional to handle this for you, head to a mechanic, local dealership, or automotive shop. You'll need to pay for the battery itself (usually $45 to $250) and, depending on where you go, the labor.

Section 3 of 5:

Weak Battery vs. Bad Alternator Symptoms

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A bad alternator causes additional symptoms like rattling and grinding. Alternator symptoms like dim headlights, electrical issues, and difficulty starting your car are frustratingly similar to weak battery symptoms–so how do you know which problem you’re dealing with? Alternator problems cause rattling and grinding sounds that are not typical of a weak battery. Also, when you start the engine, it will usually die immediately if the alternator is the problem.^{[11]
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- A bad alternator is usually caused by normal wear and tear or could be due to engine fluid leaks. Take your car to a mechanic to inspect and replace the alternator, if needed.

Section 4 of 5:

What causes a car battery to go bad?

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Age (3-5 years old or older) If you aren’t sure when you bought the current battery, check for a manufacturer date (usually found on a sticker on the top or side of the battery case). If you don’t see a sticker and can’t recall when you got the battery, it’s probably safe to assume that it’s more than a few years old and needs to be replaced.^{[12]
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- To extend the life of your battery, drive your car regularly, make sure the electrical components are turned off when you aren’t using them, and try to protect your vehicle from extreme temperature fluctuations.
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Extreme temperatures You’ve probably heard that extreme winter temperatures can cause car battery issues, but extreme summer weather can be even more problematic. The high temperatures tend to funnel the heat under the hood, which causes the battery fluid to evaporate and shortens the battery life.^{[13]
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- The warmer the climate, the faster the battery will run out of juice.^{[14]
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  Go to source} Automotive repair specialist Duston Maynes says that people who live “anywhere that gets over 100 degree temperatures” may need to replace their battery more frequently (possibly even earlier than 3 years).
If you don’t drive your car often, or if you mostly just drive short distances, the battery may not recharge fully. If your vehicle stays parked for a long period (several weeks or months), it may naturally self-discharge over time, which causes the battery to go completely dead.
Getting your car inspected annually ensures your battery remains in peak condition since you’ll be able to stay on top of all potential problems. During a routine inspection, a mechanic will test the battery’s charge, make sure the terminals are in good condition, and double-check that the battery is mounted properly in your vehicle’s engine bay.^{[15]
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Section 5 of 5:

Can I drive my car with a weak battery?

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Driving with a weak battery is OK in the short term, but replace it ASAP. A weak car battery still has a little juice left, but it’s hard to tell just how far that juice will actually get you. Plus, you can expect the battery to get weaker and weaker–eventually, it will die and you could end up stranded somewhere if you aren’t prepared. Driving with a weak battery also causes problems with your vehicle’s other components, like the alternator, so it’s best to deal with it as soon as you notice symptoms.^{[16]
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- According to professional auto mechanic Jason Shackleford, “Diagnosing battery issues at home is rather difficult and not very accurate. Most auto parts stores and some repair shops will usually test your car battery at no charge.”