How To Charge A Car Battery

Updated October, 2020
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To charge a car battery, you need to follow the proper steps and stay safe. Wear appropriate safety equipment, identify the terminals, disconnect the battery cables, clean the terminals, set to the appropriate voltage, attach the charging cables, and plug in the charger.

Things you should know before you charge a battery

Batteries can be extremely hazardous. It's important to know what you're doing and the parts of the battery before attempting to charge it. Without the proper knowledge, you could breathe in hazardous fumes or make the battery explode.

Terminals

Terminals are metal nodes used for transmitting electrical power to your car. Each battery has 2 terminals, a positive and a negative terminal.

  • Positive Terminal - This terminal usually has a red color and a plus sign next to it.
  • Negative Terminal - This terminal is typically black with a negative symbol next to the terminal.

Battery Acid

Battery acid is a type of sulfuric acid. It's a sulfur and water solution. Sulfuric acid can give off potentially dangerous fumes in the form of hydrogen gas.

Amp Hours Rating

Amp-hours is how many amps an hour a charger can put out. If a battery has 36 amp-hours, it can output 1 amp for 36 hours, 3 amps for 12 hours, 6 amps for 6 hours, etc. A 10 amp charger puts out 10 amps an hour to the battery.

Voltage

Your battery has 6 cells with 2.1 volts each. A battery is charged to full at 12.6 volts. Even if it drops to just 12 volts, the battery is working at 25%. The lower the voltage, the harder your car is to start.

What equipment do you need

Batteries are potentially dangerous, and you need to stay safe when working on them. Before you begin, make sure you are working in a well-ventilated area. Here are some commonly used PPE items when charging a battery

  • Safety goggles
  • Rubber gloves
  • Filtered mask
  • Long sleeve shirt

Hooking up the charger

Before you start charging, make sure you're in a well-ventilated area, and your battery and charger are compatible. Check your owner's manual for more information.

  • Step 1: Identify the positive and negative terminals. The positive terminal is either red or has a plus sign near it.
  • Step 2: Disconnect the battery cables and remove the battery. Always disconnect the negative, or ground, first.
  • Step 3: Clean your battery terminals. Make sure you remove any dirt or corrosion to ensure a proper charge.
  • Step 4: If required, fill the cells with water. If you have a maintenance-free battery, you can forgo this step.
  • Step 5: Set the charger to the proper voltage. The appropriate voltage should be on the battery or in the owner's manual.
  • Step 6: Attach the cables. Attach the positive cable first and then the negative.
  • Step 7: Plug in the charger. Make sure you're using a grounded outlet without an adapter.

How long should it take to charge?

If you know how many amp hours your battery has, you can calculate how long it takes to charge. To figure that you can use a simple formula. Time= Amp-hour/Battery Amps. For these examples, we are using a 48 amp battery.

Using 2 amps

Using a 2 amp charger on a 48 amp battery takes 24 hours to charge from empty. The charger puts out 2 amps an hour and has to work for 24 hours to reach 48 amps.

Using 4 amps

Using a 4 amp charger on a 48 amp battery takes 12 hours to charge from empty. The charger puts out 4 amps an hour and has to work for 12 hours to reach 48 amps.

Using 10 amps

Using a 10 amp charger on a 48 amp battery takes take 4.8 hours to charge from empty. The charger puts out 10 amps an hour and has to work for 4.8 hours to reach 48 amps.

Using 12 amps

Using a 12 amp charger on a 48 amp battery takes 4 hours to charge from empty. The charger puts out 12 amps an hour and has to work for 4 hours to reach 48 amps.

Using 40 amps

Using a 40 amp charger on a 48 amp battery takes 1.2 hours to charge from empty. The charger puts out 40 amps an hour and has to work for 1.2 hours to reach 48 amps.

If the battery won't hold a charge, it's time to replace

Batteries have a defined lifespan. Most batteries last between 3 to 5 years. Eventually, your battery is going to need replacement. There are different types and prices of batteries, depending on their perks.

Battery Prices

Depending on what kind of battery you need, your costs varies. If you need a battery that starts reliably and has a high reserve, your price isn't going to break the bank. The more perks you add on, the more money you are going to pay. A battery designed for cold weather costs more than a plain battery.

How to get the right battery

Batteries can be a complicated thing to understand. Between all the numbers, the sizes, and the voltages, it can be scary. However, you need to look for the size of the battery and the voltage. Your battery needs to fit in your car and have to start your vehicle. As long as those two things are compatible, you can then look for other perks.

When the time arises, is my insurance going to be enough?

When it comes to car insurance, there are several factors to consider beyond monthly cost. A policy that covers you when you need it, has a low deductible, and offers several discounts can be hard to find - which is why we've done the work for you.

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Call an insurance expert
Our team will help you find the lowest insurance prices.
866-996-3156