Learn How to Test a Battery Using a Multimeter

How to Test a Battery Using a Multimeter

Multimeter

Figure 1: Multimeter

Knowing how to test a battery using a multimeter is important to ensure the battery is working at optimal levels and is not showing symptoms of wearing out. A battery failure can lead to seemingly increasing problems in the hardware of an electronic system or starting troubles in a car. A multimeter can be used to check the voltage and current produced by a cell which helps to recognize a faulty battery that may be replaced. The symptoms of a poor battery and how to test a battery with a multimeter are discussed below.

Table of contents

View our online selection of clamp meters and multimeters!

Symptoms of a poor battery

Test the battery for faults if any of the following symptoms show up:

  • Physical issues like leaking, heating, physically broken terminals, or bulging
  • The battery is unable to hold a charge
  • The battery appears to charge to 100 percent very quickly, only to see the charge getting drained off too fast
  • The voltage across the battery terminals is too low compared to its rated voltage on the label.

How to check battery voltage using a multimeter

  1. Disconnect the battery from the circuit.
  2. Rotate the knob of the multimeter and set it to 15-20V DC voltage (a battery generates DC power). Always set the dial to a higher range than the specified voltage of the battery. For a 9V battery, selecting the 15-20V range on the multimeter dial should work fine.
  3. Connect the plug of the red probe to the VΩmA port of the multimeter, and the black probe to the COM port.
  4. Connect the multimeter leads to the battery’s terminals (red probe to the battery’s positive terminal and black probe to the battery’s negative terminal).
  5. Take the reading on the multimeter. If the reading shows a value greater than 7V for a 9V battery, the battery is still fit to use.
  6. If the reading shows a considerably low value (say <1V for a 9V battery), the battery may be faulty or dead and needs to be replaced. The battery is typically considered dead if the multimeter reads below half the voltage level specified on the battery.
Testing a battery using a multimeter

Figure 2: Testing a battery using a multimeter

How to check battery amperage using a multimeter

In most cases, the voltage across a battery can be measured to check if a battery is working or dead. But if the goal is to ensure whether the battery can supply sufficient current to a load, make sure to measure the amperage of the battery in milliampere-hour (mAh). Amp-hours and voltage are used to rate batteries. The voltage and amp-hours of the battery can be found on the battery's label. For example, 12V 95Ah indicates that the battery delivers 12V at 95 Amperes for one hour.

The following steps explain how to check battery amps with a multimeter:

  1. Disconnect the battery from the circuit.
  2. Rotate the multimeter dial and set it to measure DC of the appropriate current range (Choose 200mA if the label on the battery reads 100mAh).
  3. Connect the plug of the red probe to the VΩmA port of the multimeter and the black probe to the COM port.
  4. Connect the multimeter leads to the battery’s terminals (red probe to the battery’s positive terminal and black probe to the battery’s negative terminal).
  5. Take the reading on the multimeter.
  6. If the multimeter reads somewhere around the value given on the battery’s label, the battery works fine. For example, if a battery designed for 100mAh gives a reading of 98.5 mA on the multimeter, the battery works fine.

How to test a car battery with a multimeter

One of the most common batteries to check are car batteries. Like any general battery, a car battery can often go bad over time or fail suddenly. Even though it is more likely to happen during extreme weather, it is always a good idea to check the car battery under normal conditions too. An automotive battery measures 12.6 V or above when fully charged, and under a running engine, the value should be 13.7 to 14.7 V.

To check if a car battery has gone bad, look out for the following symptoms:

  • Horn doesn’t sound the way it used to (or the horn appears muted)
  • The brightness of the lights decreases while using the horn or indicators
  • The battery light gets illuminated on the dashboard
  • The car has a lot of false starts
  • The vehicle requires a lot of jump-starts (connecting an external power source temporarily),
  • The battery has acid spillage leading to corrosion in surrounding areas.
  • The car doesn’t start
Checking a car battery with a multimeter

Figure 3: Checking a car battery with a multimeter

How to check the voltage across a car battery using a multimeter

A car battery is usually located in the engine compartment towards one side of the engine, but can also be placed under the wheel well, the back end of the car, or even in the trunk. Refer to the owner’s manual in case of any confusion regarding the battery location. Also, access the battery terminals by looking for metal connections on the top or front of the battery. Perform the following steps sequentially to check the voltage across the car battery when the car is off:

  1. Turn on the headlights for 2-3 minutes to eliminate any surface charge on the battery.
  2. Turn off the lights.
  3. Set the multimeter dial to 15-20V (DC voltage).
  4. Connect the plug of the red probe to the VΩmA port of the multimeter and the black probe to the COM port.
  5. Connect the multimeter leads to the battery’s terminals (red probe to the battery’s positive terminal and black probe to the battery’s negative terminal).
  6. Take the reading on the multimeter.

If the car is off, a reading of 12.2 V-12.6 V shows that the battery is in good condition and fully charged, and if the measured voltage is less than 12.2 V, the battery is weak and may have to be replaced.

When the vehicle is turned on, the battery drives the starter motor, so more power is drawn from the battery. The voltage rating drops for a moment as soon as the car is turned on, but it shouldn't get below 10 V. If the measured voltage is below 10 V, the battery may not have sufficient turnover strength and may be prone to failure soon, hence may be either recharged or replaced.

Another way to check a car battery is by ensuring that it draws power successfully by testing its cold cramping amps (CCA). CCA rating gives an estimation of how efficiently the battery powers an engine at cold temperatures (typically anything below 320F or 00C).

How to test the cold cramping amps of a car battery

  1. Connect the multimeter leads to the car battery terminals.
  2. Set the multimeter dial to 15-20V (DC voltage).
  3. Fire up the ignition of the car. Keep the engine running throughout the measurement process.
  4. The reading may drop initially (say to 10V) and then return to a higher value around 12V.
  5. A constant reading after the initial drop indicates a perfect battery.
  6. An initial reading greater than or equal to 5V and less than 10 V suggests that the battery is slowly dying.
  7. If the reading is below 5V, it is better to replace the battery.

Note: While testing the CCA of a car battery, always take the help of another person. One can control the car ignition process while the other takes the measurement.

How to test AAA and AA batteries with a multimeter

When testing a battery, it's important to observe the correct polarity (positive and negative) of the battery and the multimeter probes to avoid damaging the device or the battery.

  1. Set the multimeter to measure DC voltage.
  2. Turn on the multimeter and select a voltage range that is greater than the voltage of the battery being tested. For example, if you are testing a 1.5V AAA battery, select a range of 2V or higher.
  3. Touch the black probe of the multimeter to the negative (-) end of the battery and the red probe to the positive (+) end of the battery.
  4. Read the voltage on the multimeter display. If the voltage is close to the rated voltage of the battery, the battery is good. For example, a new AAA battery should read around 1.5V.
  5. If the voltage reading is significantly lower than the rated voltage of the battery, the battery may be drained or dead and needs to be replaced.

How to test a lithium battery with a multimeter

It's important to note that Lithium-ion batteries have a limited number of charge cycles and can become damaged if discharged below a certain voltage. It is recommended to consult the manufacturer's specifications before performing a multimeter battery test.

  1. Set the multimeter to measure DC voltage.
  2. Identify the positive and negative terminals of the lithium battery.
  3. Connect the red probe of the multimeter to the positive terminal of the battery, and the black probe to the negative terminal.
  4. Check the voltage reading on the multimeter. A fully charged lithium battery should read around 4.2 volts. If the voltage reading is significantly lower than that, the battery may be discharged or damaged.
  5. If you need to test the battery's internal resistance, set the multimeter to measure resistance, and touch the probes to the positive and negative terminals of the battery. The reading should be in the range of a few ohms.
  6. Once you are finished testing the battery, make sure to disconnect the multimeter probes from the battery terminals in the correct order: first the black (negative) probe, then the red (positive) probe.

To learn more about multimeters, read our multimeter guide. Also, learn how to test a capacitor using a multimeter in our technical article.

FAQs

What should a 12V battery read when fully charged?

When fully charged, a 12V battery should read slightly above 12V (say 12.6V).

What is the voltage at which a car battery needs to be replaced?

The car manual indicates where the car battery should lie, which in most cases is approximately 12.6 volts.

How long should you run a car to charge the battery?

It is advisable to drive the car for around 30 minutes before stopping again so that the battery continues to charge.

For how long can a car battery remain dead and still be recharged?

Under normal conditions, car batteries last for approximately two weeks without starting the car.

How to test car battery amps with a multimeter?

Set the multimeter to measure current, connect the positive probe to the positive terminal of the battery and the negative probe to the negative terminal, start the engine, measure the current draw.

How to test a battery charger with a multimeter?

Set the multimeter to measure voltage, connect the positive and negative probes to the appropriate terminals, plug in the charger, and measure the voltage output.

View our online selection of clamp meters and multimeters!