Charging a dead car battery is more than simply hooking up a charger if you want to do this job safely. You should know which terminal to remove first if you have to remove the battery, which terminal to hook up first on the charger, how long to charge a dead car battery, and more.
Getting Ready to Charge
Before we get into how to charge a car battery at home, you need to know how to prepare to charge the battery. It is very easy to get a good shock if the battery does have some juice.
Before you even get started, if you have to remove the battery from the vehicle to charge it, be sure you have the tools for the job.
Some batteries are easily accessible; however, some are under or in the fender and some may even be in the trunk or under the seat depending on the make and model of your vehicle.
What to Do Before Charging a Battery
Now, let’s get into the nitty-gritty. Start with these five steps before you try to charge or jumpstart a car battery.
- Refer to your manual: Every car is different and your manufacturer might have specific instructions for your make and model.
- Be safe: Make sure you’re charging the battery in an area where there aren’t any flames, sparks, or smoke. Also, take off any jewelry, as it can be a safety hazard. Additionally, slip-on safety gloves and glasses.
- Sniff around: Do you smell something that reminds you of rotten eggs? If so, the battery might be leaking dangerous gas and you should not try to charge the battery. Stay away from the car, get it towed, and let a professional take a look.
- Check the heat: Heat rising from the battery case might mean it’s been working harder than it should. Keep the hood up and let the battery cool before trying to charge it.
- Look for corrosion: Generally, corrosion looks like a greenish, crusty substance around your battery ports. It’s a product of battery acid fumes coming into contact with the air and it’s pretty common in most lead-acid batteries. However, it can compromise your car’s electrical system and make it harder for the battery to receive the charge. You can remove the corrosion by cleaning it up with a brush and a paste-like mixture of water and baking soda.
Hooking up the Battery Charger
Follow the instructions for your particular charger. Basic instructions for most chargers include:
- Make sure the charger is off.
- Hook-up the positive cable on the charger to the positive terminal on the battery.
- Hook up the negative cable on the charger to the negative terminal on the battery.
- Set the charger to the slowest charge rate.
- Turn on the charger and set the timer.
When removing the charger, turn it off first, then remove the positive then negative cable.
How long does it take to charge a car battery?
If the battery voltage is below 11.85 and your charger is putting out a 5-amp charge rate, it will take about 12 hours to fully charge a battery with 400 to 500 cold-cranking amps. The same battery will take about 6 hours to fully charge if the charge rate is 10 amps.
The lower the open-circuit voltage in the battery and the more cold-cranking amps, the longer it will take to charge the battery.
If a cell is bad, the battery won’t hold a charge. In this case, bring your battery or your vehicle with your battery to a local Meineke Car Care Center and we will change your vehicle’s battery.
Here’s, How to Recharge Your Battery
First, find your vehicle’s battery and locate the positive and negative terminals. Most cars have their battery under the hood. The positive terminal is marked with a “+,” and the negative terminal is marked with a “-.” Sometimes the terminals are protected by plastic covers that need to be flipped out of the way, so you can charge the battery.
Next, make sure your battery charger is unplugged from the wall socket it uses household current to charge the battery and that it’s switched off, just to be doubly sure there’s no current flowing through it. Read the instructions that come with the battery charger, as each charger operates a little differently.
Attach the charger’s red clamp to the battery’s positive terminal and the black clamp to the negative terminal. Give the clamps a little wiggle to ensure that they have a good connection to the terminals. For the greatest safety, keep the charger as far away from the battery as the cables allow.
Now plug the charger in and turn it on. The Optima charger that we’re using here has a switch that sets it for either a motorcycle or car battery or one of Optima’s high-performance batteries. The Optima charger will automatically shut off when the battery is fully recharged.
Other chargers work differently; they may not shut off automatically but rather have gauges that let you know when the battery is charged. Many battery chargers deliver two to six amps (some allow you to choose the amperage level) and will take at least several hours to recharge a dead car battery. Read the instructions that come with the charger to be sure you’re operating it correctly.
When the battery is fully charged, shut off the charger and unplug it. Then remove the cables, unhooking the negative (black) clamp first.
Figuring Out the Real Problem
Remember, unless you know the reason your battery died (say, because you left the headlights on overnight) even though your vehicle starts and runs after you recharge the battery, something in your electrical system may be causing the problem. Expect your battery to run down again (and be happy if it doesn’t).
If your battery soon weakens or gives out, consider removing it and hauling it down to an auto-parts store. Many will test the battery for you, and you can pick up a new one while you’re there. Alternatively, jump-start your vehicle and get it down to a repair shop. You either have a bad battery or an electrical-system issue; you’ll need the help of a technician to solve the problem.