A car battery provides you with the electricity you need to start and for all your electrical devices to work. Although it is normally charged by the car's alternator, there are times when the battery runs out of power for a number of reasons, so it needs to be connected to a charger. When starting a car, you basically give the dead battery enough boost to start the engine and have the alternator charge it for the rest of the way. On the other hand, if you use a charger, you allow the battery to fully charge before using it again.
Part 1 of 3: Prepare to change the battery
Step 1. Read the battery specifications
If the battery is the one that originally came with the car, read the owner's manual first. This should answer important questions such as the voltage needed to charge the battery and whether to remove it from the vehicle before charging. Almost all car batteries are 12 volts, but the charging voltage can vary depending on the amount of charge the battery currently has and its temperature.
Step 2. Read the specifications of the battery charger
The battery charger will come with a manual where you will find details on proper use.
Step 3. Choose a work area with good ventilation
This will help you dissipate the hydrogen gas generated by the batteries due to the sulfuric acid contained in their cells. Always keep away all volatile substances such as gasoline, flammable materials, or other sources of ignition (eg, flames, cigarettes, matches, lighters, etc.).
Step 4. Wear protective gear
Goggles, gloves, and other protective gear are a good precaution. Hydrogen contained in the battery quickly turns to gas and expands, which can cause an explosion if ventilation mechanisms are not provided. Once hydrogen comes into contact with oxygen in the air, it will become highly flammable and can be ignited even by static electricity.
Step 5. Turn off all vehicle accessories
These accessories use electricity from the battery, so it is necessary to turn them off before removing or charging.
Step 6. Find the battery
Most batteries are located under the hood of the car or in the trunk. They can also be found under the rear seat and are sometimes only accessible from the underside of the side of the car.
Step 7. Identify the positive and ground ports on the battery
One of the ports will be grounded through the chassis of the vehicle. The other will be the "hot" port, that is, the current will flow from it to the one that is connected to ground, thus forming a circuit. There are a few ways to determine which is which:
- On the battery case, look for labels such as "POS," "P," or "+" for the positive port and "NEG," "N," or "-" for the negative (or ground).
- Compare the diameters of the battery ports. In most of them, the positive port is thicker than the negative one.
- If the battery cables are connected to the ports, pay attention to their color. The wire connected to the positive port should be red, while the one connected to the negative should be black wire.
Step 8. Disconnect the battery cables
Before removing the battery, disconnect the grounded (negative) terminal and then the ungrounded (positive) terminal.
Step 9. Remove the battery from the vehicle
For some cars, you will need to remove the battery before charging, while others will not. Follow the directions in the user manual or the battery manual.
- Generally, if the battery you are charging is from a boat, you will need to remove it from the ship and charge it on shore. You can charge it instead only if you have a charger and other materials specifically necessary for that task.
- It is recommended that you use a battery carrier to move it from the vehicle to the place where you will connect it to the charger. This will avoid putting pressure on the ends and causing acid to leak out of the vent caps, which could happen if you carry it in your hands.
Part 2 of 3: Connect the charger
Step 1. Clean the battery terminals
Use a mixture of baking soda and water to clean the corrosion present on the terminals and neutralize any sulfuric acid that may spill. To apply the mixture, you can use an old toothbrush. You can also clean mild corrosion with a wire brush. Auto parts stores sell round wire brushes that are special because they fit into the terminals.
After cleaning the terminals, avoid touching your eyes, nose, or mouth, and wash your hands immediately. Do not touch any white stains that may be found on the terminals, as it is solidified sulfuric acid
Step 2. Pour enough distilled water to fill each battery cell
By pouring water into the battery cells, the hydrogen gas disperses. Do not use tap water, as it will damage the battery in the long run.
- Replace the cell caps after pouring in the water. Most North American batteries have flame arresters. If yours doesn't have flame arresters, place a damp cloth on top of the caps.
- If the battery you have does not need you to fill it with water (known as a maintenance-free battery) or if the caps are sealed, skip this step and follow the manufacturer's instructions for charging.
Step 3. Place the charger as far away as the cables allow
This will reduce the chance that the unit will be damaged by sulfuric acid vapor in the air.
Never place the charger directly above or below the battery
Step 4. Set the charger according to the correct voltage
To do this, adjust the voltage output selector located on the front of the charger. If the battery does not indicate the required amount of voltage, consult the user manual.
If the charger has an adjustable charging range, start at the lowest level
Step 5. Plug a charger clip into the positive battery port
This step is the same regardless of whether or not you remove the battery from the car.
Step 6. Plug the second clip of the charger into the ground port
There are two different cases for connecting the clamp to ground.
- If you haven't removed the battery from the car, connect the charger's ground wire to a thick metal part of the engine or chassis. In this way, you will avoid arcing at the battery terminal and will not run the risk of it exploding. Be aware that connecting the ground wire directly to the negative battery terminal can be dangerous.
- If you removed the battery from the car, you should connect a jumper wire or battery insulator wire that is at least 24 inches (60 cm) long to the ground port. Then connect the charger clamp for the ground port to this wire. This will allow you to be away from the battery when completing the circuit in case it explodes. It is also a good idea not to face it when connecting the charger to the jumper cable.
Step 7. Plug the charger into an electrical outlet
The charger must have a grounded plug (one with three blades) and must be connected to a suitable outlet (grounded). Avoid using an adapter.
Use an extension only if it is absolutely necessary. If you need to use an extension cord, it must have a grounded (three-prong) plug and also be sized appropriately to accommodate the amperage of the charger. Do not use an adapter between the charger and the extension, or between the extension and the wall
Step 8. Leave the battery connected to the charger until it is fully charged
The best way to know is to leave it for the recommended charging time or to watch the indicator to see if it has been fully charged.
Part 3 of 3: Disconnect the charger
Step 1. Unplug the charger
Once the battery is fully charged, you will need to systematically disconnect the components. It begins with the end of the charger that is plugged into the outlet.
Step 2. Disconnect the charger clamp that is grounded at the battery
The first thing you should do is disconnect the ground terminal. Again, if you took the battery out of the car, this will be the negative terminal; however, if you didn't, you will need to disconnect the clamp attached to a metal component from the car.
Step 3. Disconnect the clamp from the positive port
This clamp will be connected to the positive port of the battery.
Some battery chargers have an engine start function. If this is your case, you can leave it connected to the battery when starting the car's engine. If not, you must unplug it before starting. Either way, avoid moving the engine parts if you are going to start it with the hood up or the cover removed
Step 4. Reinstall the battery
This should only be done if you removed the battery to charge it.
Step 5. Reconnect the battery cables
First connect the ungrounded (positive) terminal and then the one that is grounded (negative).
- For car batteries, charging times are based on their reserve capacity. On the other hand, motorcycles, lawn tractors, and deep cycle batteries are based on their amp hour rating.
- When you connect the charger clips to the battery, rock or twist them several times to make sure they are properly connected.
- Even when wearing safety glasses, stay away from the battery and turn around when making the final connection to the charger.
- The battery may also have a visual indicator whose function is not to indicate its condition, but rather to show the current charge. However, these indicators lose accuracy after the car has been driven. Basically, they are used during manufacture in order to provide the dealer with information regarding the loading of the car before it is sold.
- Never let a metal tool come into contact with the battery ports at the same time.
- Take off all rings, bracelets, watches, necklaces, or other personal jewelry before connecting the battery to the charger, as they could short-circuit, melt, and cause a serious burn.
- A higher level of current will charge the battery more quickly, but if it is too high, it will overheat and damage it. Never exceed the recommended charging range, and if the battery gets hot to the touch, stop the process and let it cool down before proceeding.
- Have plenty of soap and fresh water on hand in case you come in contact with battery acid. If this acid gets on your skin or clothes, wash it off immediately. In the event that it does get into your eyes, wash them with cold water for about 15 minutes and seek medical attention immediately.