If you're having problems with the electrical components in your vehicle and your car is reluctant to get started in the morning, it’s possible you have a problem with your battery. Your battery and your alternator are the two components that keep all the electronics in your vehicle operating smoothly. If one or the other goes bad, you're going to have a lot of trouble keeping things like your air conditioner, your radio, your power door locks, and windows working properly. If your battery dies completely then you can't create the spark needed to turn your engine over and actually get your car started at all.
Since you're not going to be able to drive your car without a functional battery, it's good to know how to make sure your battery is still good. A typical car battery should last you anywhere between three years and five years if you just got it brand new. All batteries are going to have some variation in lifespan, and a lot of that depends on how you drive your car. If you drive your car in extreme temperatures either hot or cold, if you do a lot of intense cross-country driving or you have a lot of electronics routinely running in your vehicle, your battery life is not going to be as long as it would be in some other vehicles.
Because there is such a potential range for how long your battery could last, when you start experiencing problems that indicate there may be an issue with your battery it's good to know how to test it to rule it out as either the cause of the problem or let you focus your attention somewhere else.
How to Test a Car Battery with a Multimeter
The most common way for people to test car batteries is to use something called a multimeter. A multimeter is a fairly simple device that measures voltage and when you use it with your battery it's going to let you know how much power is left inside of it.
Of course not everyone has a multimeter on hand but if you're at all interested in doing car maintenance and car repairs yourself then it's probably in your best interests to pick up a multimeter to have on hand just in case. There are a lot of symptoms that could indicate an issue with your battery that are going to require you to check it. If you have a multimeter yourself it makes it a lot easier to get this done and you can buy them on Amazon for under $15. The process for using one is fairly straightforward.
Just remember these instructions are for what are called maintenance-free batteries. Those are the ones that don't have the plastic caps on each individual cell. If you have one of those kinds of batteries, you need to use a hydrometer to test it, not a multimeter.
Step 1: You should start by turning the headlights on in your car. Just let your car sit with the lights on for about 2 minutes. This is going to get rid of any surface charge on the battery. Don't turn your car on to do this, just the headlights. That's because you should be testing a battery after it's been sitting for at least an hour without it being used. If you test your battery immediately after you've been driving your car you might get a false reading because the battery could still be holding a charge from the alternator.
Step 2: Give your battery a quick visual inspection, more specifically the terminals themselves. You want to look for any kind of corrosion or build up on them. That's usually kind of a white or yellow crust that forms around the metal terminals on a battery. If you have corrosion like that it's going to interfere with reading the battery. It could also explain why you might be having issues with your battery in the first place. If you notice some corrosion you can clean it off using a terminal brush and a battery terminal cleaner. Don't just use soap and water for this job. If you don't have any corrosion, then skip this step.
Step 3: Now that your battery is prepared you want to set your multimeter to voltage and adjust it to about 20 volts DC. Some people will tell you 15 to 20 volts but whatever you choose just make sure it's above 15 so that you get the correct reading. You can make sure your lights are turned off at this point. You may have the option on your multimeter to select an AC current. You don't want to use AC. We're only measuring DC here.
Step 4: Touch the probes on your multimeter to the correct terminals of your battery. That means negative to negative, and positive to positive. Batteries and multimeters are colour coded to make this simple. If you've never done it before just remember that negative is black and positive is red.
Step 5: Check the display on your multimeter. A fully charged battery is going to measure 12.5 to 12.6 volts. Remember, that's fully charged. The colder it is, the slightly lower your reading is going to be as well. At 30 degrees you can expect a reading of 12.58. If you have a battery that's working at about a 75% charge your measurement is going to be around 12.45 volts. If you have anything below 12 volts, your battery is not working the way it's supposed to be and is basically out of useful charge.
If the range is showing somewhere between 12.3 volts and 12.5 volts, you could definitely benefit from giving your battery a charge.
Step 6: While you're still under the hood you can have somebody else turn the car on with the multimeter attached to the battery. The voltage on the battery should change at this point but should not go below 10. If your battery goes below 10, that is not producing the correct voltage to operate your car properly.
If you're getting any numbers that are indicating a problem with your battery, then your best bet at this point is to simply swap it out with a new one. If your battery is looking like everything is A-OK and you've got around a 12.6 volt reading on your multimeter, then you may need to look elsewhere to determine the source of the problems you're experiencing in your car. The best bet when it comes to electrical issues is to check out the alternator if the battery is not the source of your problems.
How to Test a Car Battery Without a Multimeter
Testing your car battery with a multimeter is the easiest and most effective way to get the job done. However, if you're in a pinch and don't have a multimeter handy there are a couple of things you can do to check out how your battery is working as well.
Step 1: You want to start with a quick visual inspection of your battery. Make sure it's not leaking and make sure the case itself isn't bulging. That can happen sometimes and cause a lot of troubles. Your battery should still be a perfectly straight sided box. Check for the corrosion that we mentioned before around the terminals. If everything looks good, then you can move on.
Step 2: You can start testing your battery by turning the headlights on without turning the engine on. Leave the lights on for about 15 minutes.
Step 3: With the lights still on, crank the engine and see what happens. You might need someone in the car to help do this while you check out the headlights. You should notice a very slight dimming of the bulbs as the vehicle starts. If the headlights get extremely dim or turn off while the engine takes a bit of time to turn over, and especially if you notice any kind of clicking noises, then you definitely have a problem with your battery. What we're seeing here is that your battery isn't generating the voltage to get your car started.
Obviously, this is nowhere near as accurate as using a multimeter and can't give you specific numbers, but it is a practical example of whether or not your battery is working for you.
Signs of a Bad Car Battery
Obviously if you're testing your battery then you think there's a problem with your battery in the first place. And it's true there are a number of signs you can be on the lookout for that will indicate you're having an issue with your battery. We've already addressed corrosion so let's take a look at what else can tip you off that it might be time to test your battery to see if it's working okay.
Like we covered in the test that doesn't use a multimeter, dimming lights is a potentially good indicator about the strength of your battery. This is going to cover not just your headlights but the interior lights of your vehicle as well. You'll also notice issues with your other electrical components such as power windows or anything you might plug in like a phone charger. The other components are likely to fail out right, but dim lights are the best visual cue.
Slow Engine Starting
This is often the first sign that people get when there's a problem with their battery. When it's not working the way it should because it doesn't have the charge, then your starter motor isn't going to come on right away to get your engine to turn over. If this is a consistent issue every time you try to start your car, then it's a good sign you have a battery issue.
If your battery is unable to transmit the current to the starter then you're likely just to hear a series of clicks as you try to get your car started and nothing else. At this point your battery is likely completely dead and your car will not start at all.
Battery Light or Check Engine Light
Indicator lights on your dashboard can often be pretty vague, but when your battery is failing, you're likely to get a warning light that pops up on your dashboard to let you know. Some cars may just throw up that check engine light first, while others will give you the battery light to let you know that there's a problem. If you get that along with some of these other symptoms, then it's a good bet your battery has a problem and you may need to replace it.
Cost of a New Car Battery
When it is clear that you need a new battery then luckily there are many places that you can pick up a new one. As with most parts of a car, a new battery for your vehicle comes with a range of prices. You can probably pick up a brand-new battery for anywhere between $50 and $150. There are also some premium batteries that may cost you as much as $300 or more. That's not necessarily something you need for your car and certainly not standard or required by any means. It's also worth noting that you can save yourself some money on your car battery by replacing it yourself rather than heading to a mechanic. A lot of people are intimidated by doing any kind of work on their vehicle but replacing the battery is one of the easiest things that you can do, and it’s not going to take a lot of time either. If you're not exactly sure how to get the job done, there are lots of videos that you can watch like this one which can guide you through the process of swapping an old battery for a new one.
The Bottom Line
Although it can be difficult sometimes to pinpoint the nature of an electrical problem in your car, whether the battery or the alternator is to blame, testing the battery is the best way to figure out if it's the problem or whether you should be focusing perhaps on the alternator. Like we said, a multimeter is a valuable tool for this, and they are really affordable. If you're not comfortable using one or you don't want to invest in one you can go to a mechanic to get this job done for you but remember that just visiting the mechanic to do this is probably going to cost you quite a bit more than just getting the multimeter yourself would. If you have your own multimeter, at least you can do this job again later as often as you need.