Skip to main content

Car Battery Maintenance

Car battery maintenance is one of the most common and critical tasks a car owner can do to prolong the service life of the battery and keep the car running.

First, you'll need to know how to identify the positive and negative terminals on your battery.

It may seem a simple task, but once you have this knowledge, you can:

  • Remove and install the battery properly
  • Test battery terminals
  • Jump-start your car
  • Check battery open voltage
  • Use a battery charger
  • Check starting issues
  • Make sure the alternator is charging your battery

Sometimes, these tasks are part of many other diagnostics procedures you may need to do when troubleshooting starting, charging, and other electrical issues.

The following sections describe these simple tests you can do at home to take care of your battery.

Before you start, it's a good idea to have the car repair manual for your particular vehicle make and model. If you don't have this manual yet, you can buy a relatively inexpensive copy through Amazon.

Haynes manuals include:

  • Step-by-step procedures
  • Photographs and images
  • Systems descriptions
  • Diagnostics and troubleshooting instructions
  • Parts location
  • Parts and bolt torque specifications
  • Electrical diagrams
  • Maintenance schedule

Following the maintenance schedule alone can save you from unnecessary breakdowns, spending money unnecessarily, and help your engine last longer. So, you'll recoup your small investment in a short period.

Here are a few simple but essential procedures you can do at home that can help you with common troubleshooting procedures.

In This Article

1. How to Identify Positive and Negative Battery Terminals
2. How to Remove and Reinstall Your Car Battery
3. Are Your Battery Cables Properly Connected?
4. Is Your Battery Properly Charged?
5. How to Jump Start Your Car
6. Is Your Alternator Charging the Battery?
7. How Do You Connect a Battery Charger?
8. Resources to Help You With Battery Related Problems

Identify the positive (+) and negative (-) post by the signs next to them.

Identify the positive (+) and negative (-) post by the signs next to them.

1. How to Identify Positive and Negative Battery Terminals

You can identify the positive and negative battery terminals by looking for the embossed symbols next to the battery posts:

  • '+' for positive
  • '-' for negative

Usually, you'll see a red cable connected to the positive post of the battery, and a black cable connected to the negative post. However, BMW is known for using battery cables with brown insulation for the positive post. So look for the '+' and '-' symbols instead, if you are not sure.

Telling apart these two different electrical-charge connectors helps you to perform many simple but important car-maintenance tasks, diagnostics, and troubleshooting procedures at home as described in the following sections.

Corroded battery terminals can cause many electrical problems.

Corroded battery terminals can cause many electrical problems.

2. How to Remove and Reinstall Your Car Battery

Removing and reinstalling a battery is among the most common maintenance tasks that most car owners have to do, either to clean battery terminals, recharge the battery, or simply to replace it.

Once you know how to identify battery terminals, you can perform this simple task using the following safety procedure.

  1. First, before disconnecting the battery terminals, neutralize corrosion buildup around the terminals, if necessary. Besides damaging your skin and eyes, corrosion may cause a spark and ignite flammable gasses coming out of the battery. Use gloves and eye protection if necessary. You can remove corrosion using a solution of baking soda (one tablespoon) and 8 ounces (0.3 kg) of warm water. Use soft and wire brushes to clean up the terminals.
  2. Use a memory saver to preserve your car's security codes and computer memory, if necessary. Follow the instructions that come with your product.
  3. Remove the negative (-) black cable first using a box-end wrench on the nut, while holding the cable with a pair of pliers to reduce pressure on the battery post.
  4. Use a clamp puller if the cable terminal seems stuck. This prevents putting stress on the terminal post and plates attached to it.
  5. Dip the connector in a baking soda solution if you need to remove corrosion from the inner wall of the terminal.
  6. Remove corrosion from the battery post using the battery wire brush.
  7. Disconnect and remove the positive (+) red cable following the same procedure.
  8. Remove the hold-down bracket to remove the battery.

When reinstalling the battery, follow the same procedure in the reverse order:

  • Connect the positive cable first.
  • Connect the negative cable.
  • Expand open the terminals so that you don't have to force them onto the post.
  • Don't over tighten the nuts or bolts to prevent damage to the terminals and posts.

The following video shows you graphically how to go about removeing corrosion from your battery terminals. Just remember, if you want to save car codes and computer settings, connect a memory saver before disconnecting your battery cables.

Perform a voltage drop test on your battery terminals to check the connections.

Perform a voltage drop test on your battery terminals to check the connections.

3. Are Your Battery Cables Properly Connected?

Corrosion tends to creep around battery terminals and cables, sometimes between the terminal and post, without visible signs. Other times, a damaged terminal goes unnoticed.

These types of problems create all kinds of electrical issues:

  • Battery failing to charge
  • Hard-start conditions
  • Electrical problems

Once you identify the positive and negative battery terminals, you can use this information to troubleshoot and service battery cable connections.

You'll need a digital multimeter (DMM) for this test.

  1. Visually check the battery terminals for corrosion and damage.
  2. Set your voltmeter to the DC (direct current) voltage scale.
  3. Choose an appropriate setting, like 20 volts.
  4. Remove the fuel pump fuse to prevent the engine from starting. If necessary, consult your vehicle repair manual to locate this fuse.
  5. Connect your voltmeter's red lead to the battery positive post.
  6. Connect your voltmeter's black lead to the cable terminal of the same post.
  7. Have an assistant crank the engine.
  8. Check the reading on your voltmeter.

If the voltage drop is higher than 0.2 volts, it indicates a poor electrical connection. Clean, tighten or replace the terminal. Then repeat this test.

Repeat the previous test on the negative post of the battery, this time, though, connect the voltmeter's negative lead to the post, and the red lead to the terminal.

You can actually use this simple voltage drop test on many electrical connectors, including those in the starting circuit and the charging circuit. It is a simple and effective way to test electrical issues caused by connectors and wires, harder to diagnose otherwise.

Use a digital multimeter to test your battery's open voltage.

Use a digital multimeter to test your battery's open voltage.

4. Is Your Battery Properly Charged?

This is another useful and simple test you can do at home.

Use this test when one or more of the following conditions appear:

  • Battery charge problems
  • Hard to start your vehicle
  • Vehicle electrical issues appear

This test takes a couple of minutes using your digital multimeter.

  1. Set your voltmeter to read DC voltage.
  2. Choose a 20 volts setting on the DC voltage scale.
  3. Identify the positive and negative posts on your battery.
  4. Connect the voltmeter's red lead to the battery's positive post.
  5. Connect the voltmeter's black lead to the battery's negative post.
  6. Check the voltage reading on your meter.

Results

  • If your voltage reading is lower than 12.4 volts, check the battery post connections as described in the previous section.
  • If the connections are good, recharge the battery and test the charging system as described in the section Is Your Alternator Charging the Battery?.
  • If the problem continues, have the battery checked at your local autoparts store, and test for a parasitic draw, if necessary.

Consult the Resources section at the bottom of this post, and your vehicle repair manual.

Jump-start your car using a good set of jumper cables.

Jump-start your car using a good set of jumper cables.

5. How to Jump Start Your Car

Connecting jumper cables incorrectly, or in the wrong order, can cause serious damage to the battery, the vehicles' computer, electrical systems, or even yourself.

Once you identify the polarity of the battery terminals, connect jumper cables following this sequence, and don't allow jumper cable clamps to come in contact with each other while you make the connections:

  1. On the dead battery, connect the red jumper clamp to the positive (+) terminal on the weak or dead battery.
  2. Connect the other end of the red jumper cable to the positive terminal of the good battery.
  3. Connect the black jumper clamp to the negative (-) terminal of the good battery.
  4. Connect the other end of the black jumper cable to a good ground on the vehicle with the weak or dead battery. Choose a ground away from the battery, for example the alternator's mounting bracket or similar part. This will prevent a spark from igniting flammable gasses coming out of the battery.
  5. Start the car with the good battery.
  6. Try to start the car with the weak or dead battery.

You may need to wait a couple of minutes for the weak battery to receive sufficient charge to start the vehicle.

If necessary, there's a detailed article about jump-starting a vehicle in the Resources section at the end of this post. Consult your vehicle repair manual as well.

If battery problems continue, perform a simple charging system test as described in the next section. And, if necessary, have the battery checked at your local autoparts store.

Make sure your alternator is properly charging the battery.

Make sure your alternator is properly charging the battery.

6. Is Your Alternator Charging the Battery?

Often, a quick check with your digital multimeter can help you determine if your charging system is properly charging your battery.

  1. First, make sure to identify the positive and negative posts on your car's battery.
  2. Check your battery's open voltage as described in section 'Is your battery properly charged?'. If necessary, recharge the battery at your local autoparts store, or connect a charger to it as described in the following section.
  3. Set your voltmeter to read DC volts, and choose a voltage of about 20 volts on the DC scale.
  4. Ask an assistant to fire up the engine and set engine speed to about 1500 RPM.
  5. As soon as the engine starts, make a note of the voltage on the readout of your voltmeter. If this voltage is lower than 13 volts, you might have a problem with the charging system. After a few seconds, check the voltmeter reading. A good voltage reading should be about 2 volts higher than open circuit voltage, the one you measured in step 2.
  6. Ask your assistant to increase engine speed to about 2000 RPM and turn on accessories like AC, headlights, radio, wipers, rear window defrost, etc.
  7. Your voltage reading now should be about 0.5 volts higher than the open circuit voltage, the one you measured in step 2.

If you believe there's an issue with your alternator or charging system, make sure the battery terminals are properly connected. Troubleshoot the battery terminals as described in the previous section, Are Your Battery Cables Properly Connected?.

You'll find more help in the Resources section at the end of this post. Specially, check the Charging System Voltage Drop Test article. And don't forget to consult your vehicle repair manual.

Read the instructions that come with your device before charging your battery.

Read the instructions that come with your device before charging your battery.

7. How Do You Connect to a Battery Charger?

Once you identify the positive and negative terminals, you'll know how to connect a battery charger. This is a procedure that comes handy from time to time.

  • Make sure the charger is unplugged or turned off.
  • Connect the chargers' red lead to the battery positive (+) post.
  • Connect the chargers' black lead to the battery negative (-) post.
  • Plug in or turn on the charger and make the necessary adjustments, following the manufacturer's instructions that come with your particular charger.

If you don't have a battery charger, get a slow charger if possible. Also called a trickle charger or battery maintainer, a slow charger sends a small amount of current to the battery. Depending on the amount of charge needed, it may take a few hours to have the battery ready for service.

A slow charger has several advantages over a fast charger:

  • Improves chemical action.
  • Plates active materials back to the plates.
  • Helps restore a sulfated battery.

A car battery slowly degrades when not in use. If you have a vehicle or car battery that doesn't see much use, a slow charger is a must.

You can keep the slow charger connected to the battery all the time when not in use. And the battery will be ready when you need it. It'll save your battery and some money.

Make sure to follow the instructions that come with your charger.

This article is accurate and true to the best of the author’s knowledge. Content is for informational or entertainment purposes only and does not substitute for personal counsel or professional advice in business, financial, legal, or technical matters.

© 2022 Dan Ferrell