Buzz
Knowing how to test a charger, whether it's for small electronic devices or car batteries, helps you determine if the device is charging properly. The process of checking a charger is similar regardless of the battery type. You need to connect the positive and negative probes of a multimeter to the corresponding contact points on the charger. The multimeter will then display the charger's output voltage.
Steps
Testing a Small Battery Charger
Plug in the charger. To verify if the charger is supplying the expected power, start by connecting it to a power source. Plug the power cable into an AC outlet to begin the charging process. You’ll measure the voltage using a multimeter.
- If the charger has a separate On/Off switch, make sure it is set to the ‘On’ position.
- A multimeter (sometimes referred to as a ‘volt meter’) is used to check the voltage of various electrical devices. You can purchase a digital multimeter at most electronics stores or online, typically costing between 200,000 and 500,000 VND.
Connect the probes of the multimeter to the corresponding ports. Most multimeters come with detachable red and black probe wires. These are used to measure the current flowing through the terminals of the battery or charger. Insert the black (negative) probe into the ‘COM’ port and the red (positive) probe into the ‘V’ port on the multimeter.
- Depending on the model you're using, some ports may be color-coded rather than labeled with letters.
- If your multimeter has built-in probes, you can skip this step.
Set the multimeter to “DC” mode. Look for the dial that shows different mode settings on the device. Turn the knob to the ‘DC’ range and stop at the next highest setting above the charger you're about to measure. This prepares you to test the charger with direct current (DC).
- To test an AA battery with an expected voltage of around 1.5V, select the ‘2 DCV’ setting.
- ‘Direct current’ refers to the flow of electricity from the starting point to the endpoint.
Warning: Using the multimeter on the wrong setting can result in overload, or even cause severe damage like explosions. To avoid this, make sure your multimeter is set to the correct mode for the type of current you're measuring, and adjust the voltage range to be higher than the device you're testing.
Connect the black probe to the negative terminal of the charger. If the charger you're testing connects to the battery through a power input port, place the probe on the metal terminal at the end of the jack. For a charging dock like an AA battery charger, touch the probe to the exposed metal part marked ‘-’ on the edge of the charging bay.
- Some multimeters have input ports that allow you to directly connect certain types of power jacks to the tool.
Connect the red probe to the positive terminal of the charger. Place the probe on the metal terminal at the end of the power input jack. For a charging dock, insert the probe into the exposed metal part marked ‘+’ on the edge of the charging bay.
- If you reverse the terminals, the multimeter may display a negative reading (or no reading at all). In this case, simply swap the probes and measure again.
Check the reading on the multimeter display. This number represents the DC voltage supplied by the charger. A battery charger needs to provide a voltage equal to (or preferably higher than) the battery's voltage in order to charge it efficiently.
- If you're unsure about the correct voltage, consult the manual that came with the charger or check the information on the device itself.
- For example, a standard lithium-ion battery has a voltage of around 4 volts. Larger devices may use batteries with voltages ranging from 12 to 24 volts.
- If the reading is below the recommended level, it may be time to replace your charger.
Testing the Charging Ability of a Car Battery
Turn on the car's electrical system. After turning the key to the ‘on’ position, activate the headlights to drain any surface charge that may have built up in the battery. However, do not start the engine yet. Before testing the charging capacity, we'll take a ‘static’ reading to see the current charge level of the battery.
- If you wish, you can also turn on the radio, fan, emergency lights, and other electrical components to drain more charge.
- This step helps ensure that the reading reflects the true charging ability of the alternator.
Set the multimeter to “DC” mode. Turn the dial on the multimeter to the preset mode for measuring direct current voltage in the next highest range above the car battery voltage. Similar to small device batteries, a car battery uses DC to power the engine, headlights, fans, and other electrical components.
- A car battery typically provides 12 volts, which is about six times the voltage of a household battery. To prevent overloading the multimeter, ensure it is set to a higher voltage range than the battery (usually 20 DCV).
Connect the multimeter probes to the car battery terminals. The best method is to insert the probes into the space between the battery terminals and the surrounding metal components. This ensures that the probes stay in place during the measurement. Connect the negative probe first, then the positive probe.
- Once both probes are connected, the multimeter will display a reading within the 12.6-volt range. This is the static voltage of the battery, showing that the battery is charged but not necessarily indicating its ability to charge.
Tip: You can use alligator clips to secure the probes to the terminals.
Start the car. The reading on the multimeter will drop abruptly as soon as the starter motor draws power from the battery. Allow the engine to run for about 5 minutes so that the alternator can charge the battery for a while.
- If the headlights or any electrical components dim or flicker briefly when you start the car, this could be a sign that the battery is faulty.
Turn off the engine completely and check if the reading is around 13.2 volts or higher. Turn the key to shut down all systems, including the lights, radio, and other electrical devices. The multimeter will show a new reading. If the reading is higher than the static voltage of the battery, it means the alternator is functioning properly and the battery is charging correctly.
- If the reading doesn’t change, the alternator may be damaged, and you should have the vehicle checked at a professional garage.
- If you're testing an external battery charger, a reading within the same range means everything is working fine.
Advice
- If you're unsure whether the battery is charging properly or don't understand what the voltage reading indicates, take your car to a professional to have the entire electrical system checked.
What You'll Need
Testing a Small Battery Charger
- Small battery charger
- Multimeter
Testing the Charging Ability of a Car Battery
- Car battery
- Multimeter
- Alligator clips (optional)
