Feeling drained? Here’s how to charge a car battery and get on your way

How to charge a car battery
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Most of us have been in this situation before — you get in your car, make yourself comfortable, start it, and nothing happens. Nada. Zilch. You try again and the engine still won’t start.

Normally, the issue happens at the worst possible time, like when you’re on your way to a job interview or when you’re already 10 minutes late for an appointment. You might not be as stranded as you imagine. Checking the battery’s voltage will tell you what’s wrong with it. Jumper cables could get you on your way in a few minutes, and changing a battery isn’t as complicated as it might sound. Here is how to charge a car battery, and change it if that’s what it comes down to.

With jumper cables

If you’re in a hurry, you will want to get some juice into the battery quickly and get on with your day. Jumping the battery, using jumper cables to another car will get you moving, but there are portable jumpers available as well. The good news is that the car’s alternator will begin charging the battery once the engine turns on. Driving for about 20 minutes should do the trick. The bad news is that if your battery can’t hold a charge, you have to jump it every time you want to get somewhere. We don’t recommend this option.

Jumping a car is straight-forward, but you need to follow basic precautions to avoid damage and injuries. The first step is finding the battery. It’s usually under the hood, but in some cars, it’s hidden under the rear seats or tucked away in the trunk. If that’s the case, there might be a terminal in the engine bay. Locating it beforehand will save you the hassle of setting everything up and realizing your jumper cables aren’t long enough. Found it? Good, you can move on to the next step.

Make sure both cars are in park if they have an automatic transmission or in neutral if they have a manual transmission and engage both parking brakes. Turn off the ignition in both cars and remove anything covering the battery terminals, including protective plastic covers and seats. Start by connecting one of the positive cables to a positive terminal on the dead battery. It’s usually marked with a “plus” symbol or the letters POS. Connect the other positive cable to the good battery, and carefully connect the negative cable to its negative terminal. The negative terminal is marked with a “minus” symbol or the letters NEG. Finally, connect the last negative terminal to an unpainted metal part of the engine bay, preferably one that is not right next to the battery. It’s very important to make sure the cables are on tight; the last thing you want is a cable coming loose after you start the engine.

If everything looks good, start the car with the good battery and let it run for a few minutes to send juice to the dead battery. Start the car with the dead battery. If it starts, great, but make sure to keep it running (and, preferably, drive it around for 15-20 minutes after removing the cables) because it might not start again if you don’t. If it doesn’t start, either your battery is completely dead or your problem comes from elsewhere. What happens (or doesn’t happen) when a car refuses to start tells you a lot about the problem. A clicking sound sometimes indicates a starter motor issue; the engine turning over but not firing signals a fuel delivery or a spark issue (like bad spark plugs).

With a portable charger

If time permits, or if you don’t have access to jumper cables, you either need a portable battery charger or you need to remove the battery and take it to an auto parts store (more on that in a moment). Investing in a portable charger is a good idea — many feature flashlights and USB ports for smartphone charging — but most parts store will top up your battery for free. To recharge via a portable charger, simply attach the positive clamp to the positive battery terminal (red to red) and the negative clamp to the negative terminal (black to black). Then, plug the charger into a regular household outlet and turn it on. Your car isn’t a laptop; keep in mind charging a battery can take eight or more hours depending on the type of charger you’re using and how much electricity it needs. Modern battery chargers usually have lights that tell you when the battery is fully charged.

Replacing a dead unit

A battery that won’t take a charge needs to be replaced with a new one. Luckily, that’s straight-forward, too. You can save a good deal of cash by changing it yourself. You need basic wrenches (often a 10mm, but double-check because some cars require a different size), and we recommend buying sandpaper to clean the terminals. Keep in mind battery acid is corrosive; it can burn your skin and it will chew right through your clothes. You can avoid both by being careful, but it is always a good idea to wear gloves and old clothes you don’t care about damaging.

Put your car in park, or engage first gear if you have a manual transmission, and set the parking brake. Assuming you already found your battery, use the correct wrenches to loosen the battery terminals. Check for white or blue-ish build-up around the terminals, wipe it off using a rag, and use the sandpaper to remove any additional build-up on both the car and the battery terminals. Once they are off, you are ready to remove the battery.

Find the bolts that secure the battery to the battery tray and remove them. In some cars, a bolt holds down a metal plate near the base of the battery. In others, two bolts connected to metal rods firmly clamp down the battery. Either way, make sure not to lose anything you remove. Set everything aside and you’re ready to pull the battery out. Installation is the reverse of removal. Tighten the bolts that hold down the battery and the ones on the terminals, make sure everything looks good, and start the car. It should fire right up.

You can’t simply throw your old battery away. You need to take it to a place that will recycle it properly. Most auto parts stores will do that. Alternatively, if you are feeling adventurous, you can take your battery to a scrap metal place and get cash for it. How much they give you largely depends on the price of scrap metal, which fluctuates like the stock market. Don’t expect a fortune unless you’re bringing two dozen batteries, but anything that offsets the price of a new battery qualifies as a win in our book.

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