How to Charge a Car Battery at Home

Jun 04, 2024

If your car doesn't start, the battery might be low on charge, and you can address this at home without visiting a garage.

There are a multitude of reasons to charge your car's battery, with the big one being to extend its life so that you don't have to buy a replacement. For those vehicles that get stored during the off-season or those that don’t have enough juice, you can utilize a wide range of chargers that cater to most budgets.

Starting from the types of car batteries to the process of charging itself, here are the basics to get you started on your weekend project.

Charging a car battery is essential, so maintaining it can mean the difference between your car running or not. One way to ensure they last a long time is to make sure they always have some charge in them. You can do this with one of two types of chargers available for purchase: trickle chargers or battery chargers. These types of chargers look quite similar, but their functionality is quite different.

Trickle chargers are strictly used to maintain batteries for vehicles that aren’t commonly in use. This can be a vehicle that is stored over the winter or a vehicle that isn’t driven every day. This kind of charger prevents batteries from going completely flat and staying like that for long since this can damage the cells and prevent them from recharging in the future.

There are primarily two types of battery chemistry: the older style lead-acid and the newer, more energy-dense lithium-ion technology. Both batteries serve the same function, although at drastically different calibers. Lithium-ion batteries provide 100% of their rated power at all power levels, whereas their counterpart, lead-acid batteries, only provide about 50% of their rated power to promote longevity.

It's worth noting that only a small proportion of cars that are not plug-ins or hybrids have lithium-ion 12-volt batteries. They are almost exclusively mild hybrid vehicles that feature the lightest form of automotive electrification.

Generally speaking, most car batteries are located underneath the car's hood. Some car manufacturers have moved the battery to the trunk, while others have it placed underneath one of the front seats. Referring to your owner’s manual is therefore your best bet if you have difficulty locating your battery in the usual spots.

Once you’ve located your battery, it is important to note which terminal is positive and which is negative, as these are not interchangeable. Connecting cables to the incorrect terminals or in the wrong manner may result in damage to the electrical components of your vehicle or even injury to yourself if you're not careful.

Charging your battery isn’t a difficult task, as most chargers automatically detect what type of battery you have and how much voltage you need to charge it. Typical 12-volt car batteries can be charged at 6 or 12 volts, although the latter is considerably quicker.

If you own a classic car that has a 6-volt battery and electrical system, though, it is essential to never charge it at 12 volts because it will cause damage. Charging the battery is not a difficult task and can be done in or out of the car. Vehicle owners who store their vehicles in unsecured locations may benefit from removing the battery and charging it inside.

To charge your battery, first, connect the battery charger to an outlet and connect the red cable from the charger to the positive terminal on your car battery. Following that, connect the black cable to the negative terminal, which refers to the ground. This should then begin the charging process, which, if the battery is completely dead could mean you will have to keep the charger connected overnight.

One of the most common charging issues is corroded terminals that cannot properly conduct electricity. These can be cleaned with metal brushes and dedicated cleaners, although this is only necessary if the battery has been truly neglected over the years.

The other explanation for the inability to charge a car battery is bad battery cells. The life expectancy of batteries is limited, although it can be extended with proper maintenance. Because of this, batteries in any vehicle will need to be replaced every four to five years. Battery cells can lose capacity prematurely through repeated cycles of being fully drained and being charged from flat to full.

With the variety of accessories and amenities that are equipped in vehicles nowadays, regularly inspecting, cleaning, and testing the batteries are all good habits to develop. This will ultimately reduce the likelihood of the battery breaking down due to electrical failures, extend the longevity of the battery, and promote safety for vehicle occupants.

Based on the East Coast, Joshua Ko has been an automotive writer for MakeUseOf for over a year and is a die-hard European car enthusiast. He primarily covers car tips and tricks and DIYs. After graduating from the Pennsylvania State University, he spends most of his time outdoors, writing, or in the garage.