How To Test A 12-Volt Battery Charger?

A battery charger is an essential gadget given its role in recharging car batteries. If a vehicle’s battery runs out flat, the alternator should ideally not be used in resurrecting such battery, rather, this becomes the job of the battery charger.

However, if unsure of the working condition of the battery charger in terms of the resistance in its lead wires and its voltage output, its charging efficiency will remain unknown

So, how do you test a 12-volt battery charger? Thankfully, testing a 12-volt battery charger or any other battery charger follows quite a few simple steps that can be easily performed by almost anyone. 

Such a test aims to determine the charging efficiency of the battery charger. This is done by checking if the lead wires used to connect to the battery terminals have any form of resistance to the flow of current. If so, this may impede the flow of charge to the plugged battery and result in a poorly charged car battery.

Also, such a test is aimed at determining the exact voltage output of the battery charger. For a battery charger designated for a 12-volt battery, ideally, the voltage coming out of it should correspond to its designation. Values considerably lower than that could be considered a pointer to a faulty battery charger, requiring it to be replaced.

So, let’s take a look at the step-by-step approach to testing a 12-volt battery charger. Every owner of a battery charger must learn the procedure for testing for the functionality and working condition of the battery charger and do this every once in a while, to ascertain that the battery charger is in good working condition.

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Step-by-step guide on how to test a 12-volt battery charger

Here is a step-by-step guide on how to test your 12-volt battery charger with ease. Follow these steps carefully to determine whether it is time to replace your battery charger.

Step 1

Testing the voltmeter

Testing a 12-volt battery or any other type of battery mostly involves a voltmeter. Therefore, the first step is to get the voltmeter ready for this. before using the voltmeter to test whether the 12-volt battery charger is working or not, the voltmeter itself must first be tested.

So, how do you test the voltmeter? It is first to rest from volts to ohms (the SI unit of resistance). This is testing how much resistance the voltmeter’s lead wires pose to the flow of electric current.

The voltmeter has two leads, after resetting the voltmeter dial to ohms, the two leads should be used to touch each other, that is, they should be brought together while taking note of the reading on the voltmeter. Ideally, this reading should fall within the range of 0.00 to 0.05 ohms. 

When the reading of the voltmeters says 0.00, the interpretation of such reading is that there is zero resistance in the voltmeters lead wires to the flow of electric current. This means that the voltmeter’s lead wires are in good working condition and that there is no break anywhere within the wire posing resistance to current flow.

Step 2

the 12-volt battery charger has two lead wires designated positive and negative similar to those of the voltmeter lead wires. They are used to connect to the car battery when charging. Once the working condition of the voltmeter is ascertained, the next step will be to carefully connect the lead wires of the voltmeter to those of the 12-volt battery charger.

Do not stress yourself out trying to ensure a particular lead on the voltmeter is connected to a certain lead on the battery charger as this does not affect the testing process in any way. Simply ensure that one of the voltmeter’s leads is connected to the negative lead on the battery charger.

Step 3

the essence of the connection made above is to test the lead wires of the battery charger, that is, to determine whether there is any r resistance in the battery charger’s lead wires against the flow of current.

Therefore, once this connection is done properly the expected reading in ohms on the voltmeter should be within the range of 0.00 to 0.05. 

a reading of 0.00 signifies zero resistance in the lead wires of the battery charger. Now that it has been determined that both the lead wires of the voltmeter and those of the battery charger do not pose any resistance against the flow of current, you can now move to the next big step in the testing procedure.

Step 4

Remember, at the very start, the voltmeter dial was reset to read in ohms, the unit for resistance. Now, reset the dial once more to the highest volt setting on the voltmeter for the next steps to follow.

Step 5

After setting the voltmeter to measure in volts, a specific voltage can then be chosen and the battery charger set to charge at such voltage.

Step 6

the last and final step in the testing procedure involves using the power lead on the voltmeter to touch the power lead on the 12-volt battery charger.

Check the voltmeter for a lead-colored black, the represent the ground lead, while the negative lead of the battery charger represents its ground lead.

The ground lead of the voltmeter, that is., the black lead should at this point be used to touch the ground lead of the battery charger, that is, the negative lead wire.

Check the voltmeter for reading in volts once these connections have been well established. Ideally, the voltage reading expected on the voltmeter should be the same as that which was present in the battery charger before this connection.

If the reading obtained from the voltmeter is short or different from the voltage setting on the battery charger, this would mean a problem with the battery charger. such charger should therefore be replaced to avoid causing any damage to the plugged-in battery or inadequate charging of the battery.

how to test a 12-volt battery?

Similar to how the 12-volt battery charger can be tested and checked for proper working condition, the 12-volt battery itself can also be tested.

The testing process also involves the use of a voltmeter. A multimeter that can measure both voltage and amperage can also be used instead.

The 12-volt battery is a common type of battery found mostly on motorcycles as well as some cars.

Measures to take while testing the 12-volt battery

When using a multimeter for this process, remember the device can measure voltage, resistance as well as current. Therefore, ensure it is set at the appropriate scale at a time.

Also, ensure not to measure the battery voltage right after it’s just been fully charged. and put on some goggles to protect your eye during this testing.

How to test the 12-volt battery using a multimeter?

Learn the dial selection on the multimeter. The multimeter can take of three parameters, its dial can therefore be set for any of these parameters. The multimeter can take off the resistance, current as well as voltage.

Omega denotes resistance, ‘A’ denotes current while the letter ‘V’ denotes voltage. On the multimeter, the voltage reading span from about 200 millivolts to 500 volts.

Aside from omega, A, and V, the dial selection on a multimeter is also  DC and AC, that is, direct current and alternating current respectively.

While DC is denoted by a straight line or no line at all, AC is represented by a wavy line.

To test the 12-volt battery, the multimeter should be set the DC voltage within the 12-volt range. 

Step 1

The first step in testing the 12-volt battery is to remove the lead wires attached to its terminals and disconnect the battery completely from the charging circuit in the car. This way, the external source of current is tapped into and whatever reading is obtained can be trusted.

step 2

look for the lead-colored red, plug this into the port on the multimeter designated V-omega.  Similarly, the lead-colored black should also be plugged into the port designated COM. 

Step 3

Once these connections have been properly done, the black lead wire can be used to touch the negative terminal of the car battery while the lead-colored red can be used to touch the positive battery terminal. this creates a complete circuit and produces a reading on the multimeter.

Step 4

Read the multimeter. A 12-volt battery in good working condition should give a reading of 12 volts (normal range: 12-12.8)

How to test the 12-volt battery using a voltmeter

Step 1

Connect alligator clips to the voltmeter leads

Step 2

Connect the battery cables

Step 3

Connect the voltmeter leads to the positive and negative battery terminals and start the car ignition

Step 4

Take the reading on the voltmeter. Expectation: a voltage drops below 9.5. values below this imply the battery needs to be replaced

How To Test A 12-Volt Battery Charger – Conclusion 

Testing the 12-volt battery is a necessary exercise and should be done every once in a while, to ensure the charger is in good working condition and produces the required voltage output. The 12-volt battery can be tested too using a multimeter or a voltmeter.