You need to recharge a car battery, but you’re not sure exactly what to do. Proper charging of a dead car battery is very important to maintaining and extending the life of the battery. Charge it too slowly and it may not be ready to use by the time you need it. Charge it too fast and you may end up destroying it. In the following paragraphs, you will find a list of steps to take to properly recharge a car battery.
Removing from Car
If you’re going to take the battery out of the car to recharge it, there are certain things you need to keep in mind. First off, remove the negative cable first. This way you’re going to have much less chance of shorting the battery out when you remove the positive terminal. After removing the negative cable and setting it aside, remove the positive cable and set it out of the way. Remove the battery hold down next. Carefully lift the car battery straight up and out of the battery box. Never tilt a battery more than twenty to twenty-five degrees on any side to make sure the electrolyte isn’t allowed to leak out. With the battery out of the car, wash it down with a solution of baking soda and water and rinse it thoroughly. Place the battery on a piece of wood on the ground; never set it on the concrete. Doing so can cause the battery to lose usable life.
Clean Battery Posts or Screw Terminals
Use some light sandpaper or a battery terminal cleaner to clean the battery posts until they are shiny, and the battery cable ends to ensure they make good contact.
Check Level of Electrolyte
Whether in or out of the car, before you recharge a car battery, carefully open the vent caps and check the level of the electrolyte in the individual cells. Inside the cell, just under the cap is a neck and at the bottom of that neck is a lip. That lip indicates proper fill level for the electrolyte. If any of the cells are low, use distilled water or battery electrolyte to refill. If using actual electrolyte, use extreme caution, as is it sulfuric acid.
Connect the Charger Leads
Battery charger leads are color coded. The red lead goes to the positive terminal (+) and the black goes to negative(-). Make sure the battery charger is unplugged and turned off before connecting it.
Turn it On
With the leads connected, plug the charger in and turn it on. If your car battery charger has selectable output levels, select the lowest level to begin. Increase the output until doing so doesn’t cause an increase in charger output. Average charge times will run around two hours for a moderately dead car battery. An extremely dead car battery can take as much as four hours to receive a full charge.
Every hour or so, check the rate of charge. You want to keep the charge rate at around ten amps for as long as possible to make sure that the battery receives as much of a complete charge as possible. Once the charge indicator reads as close to zero as possible, the battery is fully charged. Turn the charger off and unplug it. Then disconnect the charger leads and reinstall the battery.
You now have the information you need to properly and safely charge a dead car battery.