How To Know If Your Car Battery Needs To Be Replaced?

The UK’s battery experts answer the question: “How to know if your car battery needs to be replaced?”.

We’ll give you very clear advice on how to tell if your car battery is dead.

You’re probably here because you’ve been having some issues with your battery and you’re wondering whether there’s some action you can take to improve it or whether you.

It’s unfortunate that you’re having issues with the battery, but the good news is that you’re here. We’ll help. We’ll describe exactly what steps to take to find out if you need to replace your battery.

We’ll describe how you can identify your battery issues, some of the type of problem that can crop up, and what these mean about your battery’s condition.

The most important thing to be aware of is that battery problems DON’T necessarily mean it needs replacing. It may simply need charging, and there be some simple things you can do to resolve the issue.

And it’s good you’ve come to us, because when a car battery seller gives advice on this topic, hey ho big surprise: they recommend that you need a new battery.

Read on and let’s get to the bottom of the issue, and take action to fix it!

how to know if your car battery needs to be replaced

How To Tell If Your Battery Is Dead: Step By Step

How do you know if your battery has some kind of fault?

Presumably, there are some symptoms showing up to make you believe this.

So the first step is to identify the things that indicate you have a battery issue.

Step 1: Identify the sign that there’s a problem with your battery.

These signs could be:

1) Failure to start easily

This is the most clear and evident signal of a battery problem.

You turn the key or push the ignition switch and *cough, splutter, groan*. The worst feeling and sound in the world, non? Especially when it’s when you have that big, important meeting at work that morning…

The engine is failing to start or it’s turning over several times before the engine starts.

Maybe it didn’t start at all, or maybe after persisting you eventually got it to start. Either way, it’s a sign of a problem and you’ll want to investigate it, post haste.

Flickering lights or a strange noise, such as a clicking sound, coming from the engine when you start are other signs of battery trouble.

It’s not necessarily the battery to blame, we’ll talk about other possible causes later.

2) Check battery warning light on your dashboard

When this light pops up, it could be a sign that there’s a genuine problem with your battery. These dashboard warning lights are notoriously imperfect, indicating problems where none exist, but it could be real.

It’s likely to mean the vehicle’s sensors have noticed that the battery isn’t being charged properly. It could be a battery, alternator or electrical system fault.

If it’s just this warning light alone giving you the sign of a battery problem, it’s worthwhile to take the steps on this list anyway to potentially prevent an issue before it really rears its head.

If this warning light has come on and you’d already noticed one of the other problems mentioned, that could be a confirmation of the issue.

3) Weakening of your car’s electrics

This is when you’ve noticed that some of the car’s electrical systems are fading in power at times or perhaps they’re constantly weaker than they were before.

Your headlights may seem perpetually dimmed compared to their previous luminosity. Or perhaps they flicker from time to time, or dim for a while and then become brighter again.

Electric windows may seem to taking much longer than usual to go up and down. Heaters and air conditioning may seem less strong and less effective than they were before.

Other symptoms include:

  • Dashboard lights flickering
  • Seat heating system has stopped working or is hardly working
  • Sound system/radio isn’t working or has power issues
  • Phone charger has stopped charging

4) The vehicles stop-start function isn’t operating

Vehicles with stop-start functionality monitor the current being drawn from the battery. If they detect some issues with that current, it may automatically shut off the start-stop system.

It does this because it has analysed your electrical system and determined that using the start stop system may drain too much power from the battery and cause your car to be unbale to get started.

If this is the only symptom you’ve noticed, it could be a problem with your start-stop system rather than the battery.

Step 2: What caused the problem, and what’s the solution?

Here are the things that could have caused the battery issue.

Here’s the difficulty with battery difficulties – the problems that show up when a battery is simply lacking charge are the same as those that show up when the battery is dying, and will completely fail soon.

We’ll show you exactly how to identify which one of these it is:

1) Cold weather

Have your battery problems developed at a time when it has been really cold?

That can hugely affect how well a car battery works.

If the only issue you’ve noticed has been the car taking longer to crank and get started, it may be due to the weather. If it’s cold enough, it can cause the car not to start at all.

Why does it have this effect? Your battery doesn’t like extreme temperatures, whether it’s too hot or too cold. It doesn’t like the cold. Here’s why:

The chemical reactions that are needed for a battery to deliver power are slower and there are less of them when the temperature is low.

Cold temperatures actually have a double effect on your ability to start your vehicle. Those are:

  1. Your battery’s starting power is less than normal due to its chemical reactions being slowed down, as mentioned above
  2. Your engine needs more power than normal to get started. That’s because the engine oil moves more slowly than it does in normal temperatures.

The effect of chilly temperatures on the starting power of your battery and the power required by your engine to start are a lot bigger than most people assume.

TemperatureStarting Power Needed To Start EngineStarting Power of Battery
27°C100%100%
0°C155%65%
-18°C210%40%
-30°C268%18%

As you can see when we get to 0°C, your battery provides only 65% of the full power it would have at a normal temperature (27°C). And yet the engine needs more than 50% of the same power it would need to start at a moderate temperature.

That double whammy makes it clear that cold temperatures could well be the reason why your car won’t start.

Your car not starting in cold weather doesn’t necessarily mean the battery is dead!

A particular sign to show that the cold weather is the cause of your battery fault: when your battery won’t start in the morning, but starts much easier later on when it’s warmed up.

The Solution:

There are a few solutions to this one:

  • Store the car overnight in a garage, if you have one.
  • Get a jump start from another vehicle
  • Get a jump starter (like this NOCO jump starter) and have it ready for those cold days.
  • Replace the engine oil. Old, expired engine oil can be contaminated and when it’s cold it moves even slower. Replacing it with fresh engine oil can make it easier to start your car.

2) Leaving your car unused for too long

Do you just occasionally use your car? Or do you go away on trips and not use your car for weeks at a time? Have you been on holiday recently and the car went unused during that time?

Or do you use your car often, but only for short journeys? Do you very rarely go on journeys of an hour or more?

If your answer to any of these questions is yes, it may be that your vehicle battery isn’t getting a deep enough charge. That could be the reason why it’s showing signs of weakness or potential failure.

Sometimes people assume that using a battery too often will wear it down over time, but with car batteries, the opposite is true. They cope better with regular charge-discharge cycles.

And they need a long enough time being charged by your vehicle alternator that they get charged to 100%. That’s what happens with longer journeys. If you only ever go on short journeys, it won’t get enough charge.

The Solution:

Take the car for a long drive once per week. Then you’re making it sure it gets a full 100% charge. If that solves the issue, then you’ll know that the failure to charge fully was the cause.

Better yet, get a car battery charger. Once a week, hook it up to your battery and if this was the cause, then your problems are over.

For more info, here’s how long a car battery lasts without driving. And here’s will a car battery charge at idle?.

3) The battery terminals are corroded

Open your car bonnet and check the battery terminals. Are there white or green-blue crystals or powder on the terminals?

If so, it could be that the battery terminals are corroded. This can block some of the battery’s power from reaching your vehicle.

A good connection between the battery terminals and your car’s clamps is much more important than people think; it’s crucial to allow the flow of power to the battery.

The Solution

Firstly, check the battery itself. If there’s leaking battery acid, or there’s a crack in the battery casing, it’s dead or dying and you’ll need to replace it.

If it’s just the corrosion on the terminals, as described above, you can try cleaning the terminals and removing the corrosion. This could once again allow the battery to deliver more power.

How to do this?

You can quite easily do it yourself with a cleaning agent made from baking soda, and an old butter knife.

Here are some complete instructions on how to clean the battery terminals.

4) The battery is getting old and is dying

If you’re getting the symptoms mentioned as signs of a battery problem and you’ve checked the possible causes and they don’t apply to you, it could be that the battery is coming to the end of its useful life.

In the UK, with our moderate climate, 12V car batteries last longer than they do in hotter countries, and areas like the South in the USA. In hotter climates, you can be lucky to get even 3 years, with as little as 1 year not impossible in areas like Arizona.

In the UK, you can expect a 12V car battery lifespan of around 4-5 years (or sometimes more with the best car batteries). Though of course you get extreme cases where a person used a battery for 8 years, or where it died on them after a few months.

The Solution

In this case, first you must identify if it is indeed the case that the battery is dead or dying, or whether it’s some other issue.

So now to the crux of our article:

HOW can you actually tell whether the battery is dead (and needs replaced) or whether it’s another cause?

Well firstly, check whether underusing the car, corroded battery terminals or the cold weather could be the cause, and try the solutions we mentioned earlier.

Then, once you’ve eliminated those possible causes, here are a few others:

  • Alternator problems – the alternator is what charges your car when you drive. It’s possible that it’s the alternator that is causing the problem rather than the battery itself.
  • Starter system problems – if the issue is that your car is not starting or it’s having trouble starting, then it could be a starter system fault rather than the battery itself.

Identifying the problem challenge 1:

Many of these signs of battery problems are also potentially signs of what could be a starter or alternator problem instead

Problems like these are why it’s important to identify the issue and find out whether the battery is actually dead and needs to be replaced.

If the cause is one of the problems above (alternator or starter system faults), then it WILL NOT be fixed by replacing the battery.

There’s one more challenge as well, and we mentioned it earlier:

Identifying the problem challenge 2:

Any sign that a battery is dead (eg. engine not starting, dashboard warning light, car’s electrics losing power) are also signs that a battery is simply low on charge.

So a car battery could be in very healthy condition but for whatever reason, it’s not getting a full charge, and so it appears to be failing and seems like it’s going to die.

So how can you identify whether:

a) it’s not the battery at fault at all; it’s actually the alternator or starter system

b) the battery is simply low on charge

c) the battery is dead or dying?

Well, there’s a super simple and easy solution that solves ALL of the challenges with identifying the cause of the battery issue…

The Easiest Solution To Know If Your Battery Needs Replaced

And it is… *drumroll, please*

Use a car battery tester.

Why is it such an effective solution?

Because a quality 12V battery tester will tell you both the charge level (State of Charge, or SoC), and the health of the battery (State of Health, or SoH).

Then, you’ll have a very clear answer to whether the battery is dead, whether it’s low on charge, or whether it has no problem and some other system must be to blame.

The health of a battery is measured by something called CCA (Cold Cranking Amps). This is the standard measure of how much life is left in a battery. A good car battery tester measures the current CCA value of your battery.

If you don’t have a tester, you can take it to a mechanic for testing. Just make sure it’s one you trust, since they’re incentivised to sell a new battery to you. Far too many batteries are replaced that are in perfectly workable condition. (FYI, if you’re from Glasgow, here are best prices and fitting for car batteries, Glasgow.)

Here are the UK’s best car battery testers, reviewed. Some models are fairly cheap and they can come in handy to keep an eye on your battery for many years to come, not just for your current battery.

How To Tell if Your Car Battery Is Dead?

Here’s how to use a car battery tester to easily identify if your car battery needs to be replaced.

– Step 1: Attach the clips to to the battery terminals (positive clamp connected to the positive battery terminal, negative clamp connected to the negative battery terminal).

– Step 2: Turn the tester on. Follow the steps and perform the battery test.

– Step 3: Check the results. As long as you have a quality tester, you’ll get results for battery voltage (which is a measure of charge, and battery capacity (which is a measure of battery health).

Most testers will give you a very clear indication of both State of Charge and State of Health.

Here’s how to interpret the results. There are 3 possibilities:

1. State of Charge is Bad and State of Health is also Bad

The tester may say something like “Voltage Good. Health 53%. Replace Battery.”

2. State of Charge is Bad and State of Health is Good.

The tester may say “Voltage is Low, charge your battery & Battery Health is 88%. Battery is Good”.

In this case you now know that your battery is in good condition and DOES NOT need to be replaced, you need to take action make sure it’s getting enough charge.

If you’ve tried this, and you feel like it should be charged enough (you’re going on long journeys, and not leaving it unused for long), then there could be an alternator or starter issue.

3. State of Charge is Good and State of Health is also Good.

The tester may say “Voltage is Good. Battery health is Good.”

Your battery has no problems. It has enough charge, and it’s also in good health. There must be some other reason for the issues you’ve identified.

Again, if this is the case, you DO NOT need to replace your battery.

Note: for this method to work, you must a have a battery tester that can perform a battery capacity test, not just a battery voltage test.

For more info on how to interpret, check these 12V battery voltage charts, UK.

Another alternative way to check battery health

There’s also another alternative, a similar solution to know if your car battery needs replaced. You can get a car battery monitor. This device is permanently attached to your car battery, and you can check the battery health on the App at any time (it connects via Bluetooth). The best one, AB Analyzer is the only one that measures battery health.

Any time you want to check the battery health (the current CCA value), or the current voltage, to see if the battery charge is okay, you just whip your phone out and do the tests on the App. You have to be close enough for Bluetooth, of course.

Another cheaper option, called BM2, will keep an eye on voltage – again, you can check that voltage at any time using the App.

Here are the best car battery monitors with Bluetooth.

Is there a way to improve the battery health?

Yes, many batteries can be reconditioned. In fact, a high percentage of them can be recovered to quite a good level of health.

Not all batteries can be reconditioned, but many can.

The reason is that many batteries die because of something called sulfation. Sulfation is, according to Battery Council International, the cause of death of 84% of all batteries.

Sulfation is the build-up of lead sulfate on the battery plates. It’s a natural chemical process that happens to all lead-acid batteries. The reason that it kills the battery is that the sulfate gathers on the plates hardened, in crystal form.

This causes fewer chemical reactions to take place between the battery’s lead plates and the electrolyte that surrounds the plates inside the battery. And the result of that? The battery can store less charge and deliver less power. These lead sulfate crystals grow and harden further until the battery is no longer able to produce any power. At that point it stops working.

But it’s reversible! A process called desulfation can remove it. It involves putting high frequency pulse across the battery terminals, which breaks down the sulfate crystals, causing them to return to the electrolyte. Which means the battery can once again start producing the chemical reactions necessary to provide power to the car.

Let’s talk more about these desulfation methods.

How to recondition a car battery?

There are two ways:

  1. A desulfating battery charger

We mentioned battery chargers earlier as a solution for the problem of the battery not getting enough charge.

But a particular kind of desulfating charger can actually improve the health of the battery also, and recondition it back to health.

In the last few years, the top car battery charger companies, CTEK and NOCO, have added Desulfation modes to their chargers, and there are now countless stories all over the world of people reconditioning car batteries back to health that had seemed dead to the world.

That’s why CTEK’s Recond Mode has a stellar reputation now.

And the NOCO Genius 10 has a similar wealth of success stories with reviving batteries back to health.

Basically, whenever you charge your vehicle, you can also select Desulfation mode and it will recondition the battery back to health. CTEK’s desulfating chargers perform this process with every charge cycle as a matter of course. That’s how important it is.

Here are the top desulfating chargers in the UK.

2. A desulfator

Using a desulfating battery charger is a highly effective way to regularly remove any sulfation that builds up.

But there’s another device that stays permanently on your battery and is always acting to keep sulfation away.

It’s called a desulfator. It’s not a charger, its purpose is purely to act against sulfation.

It stops it even building up in the first place. Prevention is better than cure, as they say.

The best one is the one the professionals use, it’s called F16 Pulse King. It has the best results for removing the sulfation from the battery plates, and rejuvenating batteries. It draws only a tiny current, so it won’t drain your battery. And it only sends the high-frequency pulse across the battery when you’re driving (voltage is above 12.6V), so there’s even less chance of it draining your battery.

It genuinely has the ability to potentially double your battery lifespan and keep the battery in good health for longer (easier starting and maintaining power for longer).

We’ve tested these desulfators and we’ve reviewed them. Check out the best battery desulfators UK (that actually work!).

Which car battery do I need as a replacement?

If your car battery does need replaced, how do you know which one to get?

Well, this car battery buying guide shows you exactly how to find which battery you need.

How To Know If Your Car Battery Needs To Be Replaced Summary

Thanks for reading! We hope that shed some light for you on your battery troubles.

Hopefully you now know if your car battery needs to be replaced.

We discussed the major signs that something is wrong with the battery. Failure to start, the battery dashboard warning light, loss of power to the electrics and a failure of the start-stop system are all signals to be aware of.

Then, we analysed all the potential causes of the problem. The cold weather making it hard to start, corrosion of the battery terminals, not using the car enough or too many short journeys are possible causes, If none of these are the cause then, yes, it may be the case that the battery is dead and needs to be replaced (here’s how to dispose of car batteries).

But how to tell? Many of the problem signs can also be a sign of alternator, starter problems or even just the battery being low on charge (but still being in good health).

The simplest way to find out is to use a car battery tester. It will tell if if the battery is in good health or not, as well as the current charge level. Then, you get a very clear answer and you know if the battery is dead or dying.

how to tell if your car battery is dead

If the battery is in a poor state, can it be revived?

Yes, in many cases it can. A desulfating battery charger or desulfator can do this for you.

Does this work for all batteries?

No, not if the battery is cracked or leaking battery acid or has some serious structural issue. Then it’s terminal (pun intended). But if not, one of these devices can keep your battery going for a lot longer.