The battery in your car only has a limited lifespan. On a long enough timeline, it's eventually going to die on you. But before that point, you should still be able to give your car a jump-start if you find that your battery fails and you're not able to start your car some morning. But what happens if your car won't jump start?
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The first thing you need to do is understand what's happening when you jump start your car in the first place before you can figure out why the jump start isn't working.
What is a Jump Start?
When you jump start your car, you're getting a temporary boost for a discharged battery. Depending on why your battery stopped working in the first place, a jump start can potentially fix the problem and get things working again.
When you connect your battery to another car's battery by jumper cables, the other car's battery is able to transmit an electrical charge to your vehicle. Once enough power has been transferred through the cables to get your vehicle to start, your alternator will be able to turn on and as you run your engine, the alternator can continue the process of recharging your battery. If you let your engine run long enough, either by driving or just by letting it sit idle in this way, you could potentially recharge your battery and not have a problem any longer.
This could be all you need to do to fix the problem with a battery that died as a result of accidental drain. For instance, if you've left your lights or radio on overnight by accident and drained the battery, a jump start could get things working again properly.
If your battery has a physical problem with it, as in the case is broken or it was damaged in some way, then a jump start will not repair the battery. If it's completely frozen, you don't want to even jump start at all as that can cause your battery to explode.
How Long Does a Car Battery Last?
There isn't a hard-and-fast rule for how long every single car battery is going to last but you can definitely ballpark it. From brand-new, you can expect that a car battery should last you at least 3 years to 5 years. Some of them of course can last longer and depending on how you drive some of them won’t last that long at all. It's hard to say for sure but that does give you a general idea.
When it comes to getting your car jump-started, if you’ve had that battery in there for about five years now and you're finding that a jump start isn't able to get your car going, there's a good possibility that your battery has lived out its life and it's simply unable to function any longer. If that's the case, you're going to need to get rid of your old battery and replace it for a new one.
How to Test a Car Battery
In order to tell for sure if your car battery is dead and beyond repair the best thing you can do is test your car battery. The easiest way to do this, and the most accurate way to do it, is to use something called a multimeter. A multimeter is a tool that can test current in electrical systems and although it may seem intimidating and complicated, it's fairly simple to use. Also, they're not particularly expensive at all. If you're interested in maintaining your vehicle and doing home car repairs, then it's a good idea to have one of these on hand. You can buy a new multimeter from Amazon.com for as little as $15. They're simple to use, and it's a worthy investment if this is the kind of thing that you're concerned with.
When you use your multimeter to check your car battery you should get a reading that measures from 12.5 volts to 12.6 volts. That's what you would expect to see from a brand-new car battery and that's an ideal charge. This number is going to change based on a few factors.
One thing to remember is that in cold weather your battery is going to produce a worse charge. That's because batteries produce power thanks to a chemical reaction. In very cold weather, the chemicals in your battery move more slowly and are not able to produce power the same way. That's why it's so hard to get your car started on a cold winter morning. The battery isn't frozen exactly, but it has slowed down because of the cold temperature. So, if you're using a multimeter to check your charge on a cold day, you're likely to be getting a lower reading than you would on a warm day.
The other factor that affects the reading that you're going to get on your multimeter when you test your battery is of course the age of the battery. As we said that 12.5 volts to 12.6 volts is the ideal charge from a brand-new battery. The longer you have a battery, the lower the charge is going to get. When your battery is down to about a 75% charge the multimeter is going to read in the neighbourhood of 12.45 volts. If your multimeter is reading below 12 volts, then it's essentially telling you it does not have a functional charge that can power your car any longer.
Between 12.3 volts and 12.5 volts your charge is usable but not ideal. Around that 12.3-volt range you're really reaching the end of your battery's lifespan. You could definitely use a charge or a jump at this point. Far below that, and it's possible that even a jump-start won't work for your car.
Reasons Why Your Car Won't Jump Start
Under ideal circumstances a jump start is going to work and get your car started. There are a few reasons why a jump start will not work, however.
Battery Completely Dead: The most obvious reason why a jump start is not going to work for your car is that the battery is beyond the ability for a jumpstart to fix. If your car battery is severely damaged or the case is broken, or you've been using it for so long that it simply can't hold a charge any longer then no amount of jump-starting is going to fix it. Like we said, your battery has a lifespan of around three years to five years. If you're in this range and especially if you're beyond that, then it's no surprise why you can't get your battery jump started any longer.
Bad Alternator: The battery and the alternator work together to maintain the electrical system in your vehicle. If you jump start your battery but your car still isn't working you may want to look at the alternator as a possible cause. The alternator keeps the battery running after you start your car which is why your car doesn't die every time you turn it on and use the headlights or the radio. If your alternator isn't working, it's not going to keep the battery charged, so no amount of jumping will keep your vehicle going.
It can be difficult to determine if the alternator is the problem with your vehicle however because the signs of a bad alternator are very similar to those of a bad battery. One way to tell the difference is to look at something like your lights. If the battery isn't functioning the lights will be dimmed from the start but then brighten up later as the alternator takes over power later on. If the alternator is failing, then your lights will dim and flicker consistently.
Bad Terminals: Your battery connects to your vehicle by the terminals on top. These are the same things that you connect the jumpers to. If the terminals on your battery aren't working properly then your battery still may be fine, but the jumpstart is not going to work, and your battery won't work either. This can happen if the terminals are loose, or they're so badly corroded that power can't transmit through them. If you see a white, crusty substance all over your battery terminals that's corrosion. If the cables are loose and not snapped on tightly, then that will also cause the battery to not function even after a jump. You can clean off any potential corrosion with a wire brush and tightening the cable clamps will allow it to work properly again.
Bad Starter: When you put your key in the ignition to start your car it's the starter that gets the engine going. It transfers the power from your battery to the engine which allows the vehicle to get going. When your starter is not working, you're not going to get a crank in your engine. Instead you'll be met with a clicking sound and then nothing else happening. So even after a jump, your car won't start because the starter itself is malfunctioning.
Bad Jumper Cables: This is a problem that not a lot of people think of, but if you get a jump and your vehicle isn't working it could be a result of the jumper cables themselves not working properly. The fact is some jumper cables are very cheaply made and are not able to last for a very long time. If the cables aren't able to transmit the current properly because the wires inside have broken, or they're just not thick enough, then you're not going to get the right power from the donor battery to your battery. Also, exceptionally long cables are far less efficient at transferring power than shorter ones are. They create too much resistance and you won't get enough power transferred.
Bad Neutral Safety Switch: A neutral safety switch is a part of your vehicle that prevents it from starting when your car is not in either park or neutral. It's a safety feature because the last thing you'd want to do is start your car when you're in drive and immediately crash into a wall or something. However, if the neutral safety switch has failed on you, then your car's computer may not recognize that your car is in the right gear to start and even after getting a jump you'll still not be able to get going because your car thinks you are in drive or reverse even though you're not.
Fuel Problems: As weird as it sounds, this does occasionally come up as a reason why your car won't start after a jump. It could be something as simple as your car being out of gas. You may think that's super obvious, but there's a reason why when you call tech support for a problem with your computer the first thing they ask is if you have it plugged in and turned on. Sometimes it's just that simple. So, if you got a jump, and your car isn't starting, make sure you actually have gas in the tank still. Other issues with your fuel system that can cause the car not to start include a bad fuel pump, a clogged fuel filter, bad fuel injectors, frozen fuel lines, and so on.
Spark Problems: Similar to the issue with your starter, if you have bad spark plugs then it's possible you're not going to be able to get your car started even after a jump. When you turn the key in the ignition and the starter sends power from your battery to the engine it's the spark plugs that use that power to ignite the fuel and air mixture in the combustion chamber. If your spark plugs aren't working, then it doesn't matter if you got a jump because the spark isn't happening, and your engine won't start. It's very unlikely that all of your spark plugs would fail at the same time, but if you have a couple of them that are malfunctioning even then it's possible your car is going to struggle to get started and not work at all even though the battery is actually holding a charge.
The Bottom Line
When your battery dies and you get a jump to start your car up again, 9 times out of 10 the reason it won't start is because your battery is simply unable to hold a charge any longer. However, as we have seen, there are a handful of reasons why your battery could still be in good condition but you're unable to get started after a jump start. In order to eliminate what the problems can be you definitely want to start by checking your battery to see if it's able to hold a charge at all and move on from there. If your battery is 3 years old to 5 years old or be on that, then you can almost guarantee it's going to be time to buy a new one.