Car batteries: what you should know

Most of us don’t think much about it, but every time we get into our car and turn the key in the ignition, or press the start button, we rely on a battery. Without it, we just get clicks. Or in the worst case, silence. In either scenario, we’re not going anywhere.

If this happens with a remote control, we know exactly what’s going on, and what to do—we understand that we used those batteries up, or they got too old, and we slap another pair of AAs in there and Netflix on.

But car batteries are a little more complicated. Here are some things to know about how they work, what makes them not work, and what to do in a dead battery disaster.

All about chemistry

Much like humans, car batteries—or at least the parts that make them work—rely on chemicals and chemical reactions. In fact, batteries basically are chemicals with supporting structures and a case. The enclosures that hold the chemicals—if you want to drop some battery speak and surprise/maybe horrify your friends with your geekiness—are called cells. Which is why we see some batteries called a “D cell,” for example; it refers to the size and shape of the container. (And the name “battery” comes from the fact that it’s a collection—or battery—of cells.)

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That combination of chemicals in a battery is called—get this—an electrolyte. Yep, just like in our bodies, and just like in Gatorade. Except in batteries, the electrolyte is mostly water and sulfuric acid. (Which makes a really lousy sports drink.) A lot of people refer to it, aptly, as battery acid.

Starting the car is the battery’s main job. Once it’s running, the alternator takes over. What a lot of people may not realize is that your car battery is rechargeable; the alternator charges it every time you drive.

But if your battery gets really low in between charges, or “dies”—as most of us, being prone to melodrama, like to say—it may not have enough power to start your car.

Cause of death

So, when you do get into your car or hop on your bike and turn the key, and you get clicks or crickets—what the heck happened?

The most likely cause is leaving something on. Like headlights (if your car doesn’t have an override that turns them off when the ignition is off), or an interior light. With some keyless entry systems, if you leave the key fob in the car (like when it’s parked in your garage), it will actually continually connect with the car and drain your battery. If you haven’t driven your car in a long time (usually several months or more), you may discover that your battery power is MIA when you try to start up. Or, if your battery is a few years old, it may be that it’s just died of old age and needs to be replaced.

The good news is that your battery may not actually be dead dead. There’s a chance—just like Lazarus, or every Grey’s Anatomy patient with no pulse—that it might be resurrected. By a simple operation you may have heard of, called the jump start.

image credit: Popular Mechanics

Go ahead and… jump!

One way to be really prepared to help yourself or others in case of a dead battery is to get a portable jump start device. These are really cool because they’re very small, and can be carried in a backpack, purse, or in your glove compartment. They also usually have ports to charge your phone and other USB devices. Portable jump starters can range in price from about $30-100, but tend to hold a charge for many months, and they’re always ready if you need to jumpstart your car or motorcycle—so you don’t need to worry about getting stranded somewhere and needing to find a willing stranger who happens to have jumper cables. They’re also useful for tight spaces, in case your battery dies in a place where you can’t easily get another car within cable reach of it. Here’s an example of a mid-priced portable jump starter.

A portable jump start device
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To jump start your car or bike, simply connect the red clamp to your battery’s terminal with the red, positive (+) cap (moving the cap so you can clip it onto the terminal), and connect the black clamp to your battery’s black, or negative (-), terminal. Then start your car.

If you’re jumping from another car, make sure both your car and the “rescue” car are in Park or neutral, with both parking brakes on and ignitions off. Connect the red (+) clamps to both batteries first, and then clip one black clamp to the rescue car’s negative terminal, and the other to an unpainted metal surface on your car (not near the battery), to ground it. Start the rescue car, let it idle for a few minutes, then try to start your car—it should roar to life, as if nothing ever happened.
After you jump start your battery, don’t just park your car, or even let it idle—that won’t charge your battery to high enough levels to keep this whole drama from repeating itself. Drive it around for 15-30 minutes—that should be enough to sufficiently charge it, so that it will start normally the next time you try. If it doesn’t start up the next time, then it most likely needs to be replaced.

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