How To Find A Parasitic Battery Drain

Mobile Accessories

Are you experiencing unexpected battery drain on your cell phone? It can be frustrating when your phone’s battery mysteriously depletes faster than usual. In some cases, this could be due to a parasitic battery drain. A parasitic battery drain occurs when there is an excessive power draw on the battery even when the phone is not in use.

Finding the culprit behind a parasitic battery drain can be a challenging task, but with the right knowledge and troubleshooting techniques, you can identify and resolve the issue. In this article, we will guide you through the process of locating a parasitic battery drain on your cell phone, enabling you to preserve battery life and enjoy uninterrupted usage. So let’s dive in and discover how you can find and eliminate parasitic battery drain on your mobile device.

Inside This Article

  1. How To Find A Parasitic Battery Drain
  2. Method 1: Visual Inspection
  3. Method 2: Voltage Drop Test
  4. Method 3: Current Draw Test
  5. Method 4: Using a Multimeter
  6. Conclusion
  7. FAQs

How To Find A Parasitic Battery Drain

Are you experiencing the frustration of a constantly draining car battery? A parasitic battery drain could be the culprit. A parasitic battery drain occurs when an electrical component or system in your vehicle draws power even when the engine is turned off. This can lead to a dead battery and leave you stranded. In this article, we will guide you through the process of identifying and resolving a parasitic battery drain.

There are several methods you can use to detect a parasitic battery drain. Let’s take a look at each method step-by-step:

Method 1: Visual Inspection

The first step in finding a parasitic battery drain is to visually inspect your vehicle’s electrical components. Look for any lights, such as interior lights or trunk lights, that may be left on. Check if any electrical accessories, such as phone chargers or dash cams, are plugged in and drawing power even when the engine is off. Make sure all doors are closed properly and that the trunk is securely latched.

Method 2: Voltage Drop Test

An effective way to detect a parasitic battery drain is by performing a voltage drop test. Start by disconnecting the negative terminal of your car battery. Then, connect a digital multimeter to the negative battery cable. Set the multimeter to the DC voltage setting. If the voltage reading on the multimeter is more than 0.050 volts (50 millivolts), there is likely a parasitic drain present. In that case, proceed to the next method to identify the specific circuit causing the drain.

Method 3: Current Draw Test

The current draw test involves using a multimeter to measure the amount of current being drawn from the battery. To perform this test, reconnect the negative battery cable and set the multimeter to the DC current setting. Place the multimeter in series with the negative battery terminal, acting as a bridge between the battery and the negative cable. If the current draw exceeds the manufacturer’s specifications, you have located the source of the parasitic battery drain.

Method 4: Using a Multimeter

Using a multimeter can help you pinpoint the specific circuit or component causing the parasitic battery drain. Start by disconnecting each electrical component one by one and monitor the multimeter to see if the current draw decreases. When the current draw drops significantly, you have found the circuit or component that is responsible for the drain. Further troubleshooting may be required to identify the exact cause, such as a faulty relay, switch, or wiring.

Method 1: Visual Inspection

One of the first steps in identifying a parasitic battery drain is through visual inspection. This method involves manually checking the various components and systems in your vehicle for any signs of abnormality or excessive power consumption.

Start by inspecting the exterior of your car. Look for any lights that may be left on, such as the headlights, interior lights, or trunk light. Make sure all of these lights are turned off when the vehicle is not in use.

Next, move on to the engine bay and check for any loose or corroded battery terminals. These can cause poor electrical connections and lead to a drain on the battery. Ensure that the battery cables are securely attached to the terminals and that there is no visible damage or wear.

Inspect the interior of your car as well. Check all the switches and controls for electronics, such as the radio, air conditioning, and power windows, to ensure that they are turned off when the vehicle is parked.

Another area to inspect is the trunk. Make sure there are no aftermarket accessories, such as amplifiers or subwoofers, that may be drawing excessive power from the battery. Additionally, check for any signs of water leakage or corrosion in the trunk area, as this can indicate a potential electrical issue.

Finally, check the condition of the wiring throughout the vehicle. Look for any exposed or damaged wires that may be causing a short circuit and resulting in battery drain.

By visually inspecting your vehicle and addressing any visible issues, you may be able to identify the source of the parasitic battery drain. However, if no visual abnormalities are found, it may be necessary to move on to other testing methods to further diagnose the problem.

Method 2: Voltage Drop Test

A voltage drop test is another effective method to identify a parasitic battery drain. This test involves measuring the voltage drop across specific electrical components or connections in your vehicle’s electrical system. By doing so, you can pinpoint the exact location where the excessive voltage drop occurs, indicating a potential parasitic drain.

To perform a voltage drop test, you will need a digital multimeter. Start by setting the multimeter to the voltage measurement mode and connect the black lead to the vehicle’s negative battery terminal. Then, use the red lead to probe various components, connections, and circuits where you suspect the drain might be occurring.

While conducting the test, keep an eye on the multimeter’s reading. If you notice a significant voltage drop (typically more than 0.2 volts), it indicates that there is excessive resistance in the circuit, potentially caused by a parasitic drain. Repeat this process for other components and connections until you find the specific area causing the issue.

During the voltage drop test, it is crucial to pay attention to any unusual readings or fluctuations. These could indicate a faulty component or a wiring issue that is causing the battery drain. Remember to check both the positive and negative sides of the circuit, as a voltage drop can occur on either side.

It’s important to note that the voltage drop test requires some knowledge of your vehicle’s electrical system. If you’re unsure about specific components or connections, it’s always best to consult a professional mechanic or an automotive expert who can guide you through the process.

Voltage drop testing is a reliable method to identify the source of a parasitic battery drain in your vehicle. By systematically testing various components and connections, you can locate the problematic area and take the necessary steps to rectify the issue.

Method 3: Current Draw Test

A current draw test is a great way to identify any electrical components in your mobile phone that may be causing a parasitic battery drain. This method involves measuring the electrical current flowing through the circuit when the phone is in standby mode or turned off.

To perform a current draw test, you will need a multimeter capable of measuring DC amperage. Start by disconnecting the battery from your mobile phone. Then, set your multimeter to the appropriate DC amperage range and connect it in series with the battery and the phone’s positive terminal.

Once the connections are made, observe the reading on the multimeter. A normal current draw for a mobile phone in standby mode should be in the range of 20 to 50 milliamperes (mA). If the reading exceeds this range, it indicates a possible parasitic battery drain.

To identify the specific component causing the excessive current draw, you will need to remove and reconnect each component one by one while monitoring the multimeter reading. Start by disconnecting any external accessories, such as chargers or headphones, and see if the current draw decreases. If it does, the external accessory may be faulty and causing the battery drain.

If disconnecting the external accessories does not resolve the issue, move on to disconnecting the internal components. This includes removing the SIM card, memory card, and any other removable parts. Each time you disconnect a component, check the multimeter reading to see if the current draw decreases.

If you find that disconnecting a specific internal component results in a significant decrease in current draw, it may indicate that the component is faulty or damaged. In some cases, a software or firmware issue may also cause excessive current draw. Consider updating your phone’s software or performing a factory reset to see if it resolves the battery drain issue.

Remember to reconnect each component after testing to ensure all functionality is restored. If you still cannot identify the culprit behind the parasitic battery drain, it may be best to seek assistance from a professional technician who can further diagnose and repair the issue.

By performing a current draw test, you can pinpoint the source of a parasitic battery drain in your mobile phone. This method allows you to take targeted steps to resolve the issue and ensure you can enjoy uninterrupted usage of your device.

Method 4: Using a Multimeter

When it comes to pinpointing a parasitic battery drain, using a multimeter is a valuable tool in your arsenal. A multimeter is a versatile device that can measure voltage, current, and resistance. By using a multimeter, you can accurately detect and measure any abnormal electrical activity that may be causing a drain on your battery.

Here are the steps to use a multimeter to find a parasitic battery drain:

  1. Step 1: Begin by ensuring that your vehicle’s electrical systems are turned off and that the battery is fully charged.
  2. Step 2: Set your multimeter to the DC current setting and ensure that it is in the appropriate range for measuring milliamps (mA).
  3. Step 3: Disconnect the negative terminal of your vehicle’s battery.
  4. Step 4: Connect the multimeter in series with the negative battery terminal and the negative battery cable.
  5. Step 5: Allow the vehicle to sit for approximately 15-30 minutes to allow any electronic modules to power down.
  6. Step 6: Observe the reading on your multimeter. A normal parasitic drain should typically be around 50 milliamps or less. If the reading is significantly higher, it indicates a potential issue.
  7. Step 7: Begin the process of elimination by removing one fuse at a time from the fuse box until the current draw drops to an acceptable level. The fuse that causes the drop is most likely connected to the circuit causing the parasitic drain.

Using a multimeter allows you to measure the current draw accurately and identify the culprit responsible for the parasitic battery drain. It is essential to be cautious and follow proper safety precautions when working with electrical systems in your vehicle.

Remember to consult your vehicle’s manual or seek professional assistance if you are unsure or uncomfortable with performing these tests yourself. Electrical issues can be complex, and it is always best to ensure that the correct procedures are followed.

By utilizing a multimeter and following the steps outlined above, you can effectively diagnose and resolve a parasitic battery drain, ensuring that your vehicle’s battery remains in optimal condition and ready to go when you need it.


In conclusion, finding a parasitic battery drain can be a frustrating and time-consuming task. However, with the right tools and approach, it is definitely possible to identify and resolve the issue. Remember to start by disconnecting any aftermarket accessories and checking for any obvious signs of drain. Then, utilize a multimeter to monitor the battery drain and systematically eliminate potential culprits. Regularly maintaining your vehicle and its electrical components can also help prevent future parasitic battery drains. Don’t hesitate to seek professional assistance if needed, especially if you are unsure or uncomfortable with the troubleshooting process.


1. What is a parasitic battery drain?

A parasitic battery drain, also known as a parasitic draw, is the phenomenon where an electrical component or system in a vehicle continues to draw power from the battery even when the vehicle is turned off. This constant power drain can lead to a dead battery if not identified and resolved.

2. What are the common causes of parasitic battery drain?

There are several potential causes of parasitic battery drain. Some common culprits include malfunctioning electrical components such as a faulty alternator or starter motor, interior lights or trunk lights that fail to turn off, aftermarket accessories that are not properly installed, short circuits, or even a malfunctioning door switch.

3. How can I detect a parasitic battery drain?

Detecting a parasitic battery drain requires certain tools and a systematic process. One method involves disconnecting the negative battery cable and placing an ammeter in series between the battery and the cable. If there is a drain, the ammeter will show a current flow. From there, you can start removing fuses one by one until the drain stops or significantly reduces. The fuse corresponding to the reduction indicates the circuit where the drain is present.

4. Can I fix a parasitic battery drain myself?

While detecting a parasitic battery drain can be done by an experienced DIYer, fixing the issue may require professional help, especially if the cause involves complex electrical systems. Identifying the specific component or circuit causing the drain can be challenging, and improper repairs can lead to further issues. It is advisable to consult a qualified auto technician who can diagnose and resolve the problem effectively.

5. How can I prevent parasitic battery drainage?

To prevent parasitic battery drain, it is important to ensure that all electrical components in your vehicle are functioning correctly and turn off when not in use. Avoid leaving interior or trunk lights on for an extended period, check for any aftermarket accessories that might be drawing power, and have your vehicle regularly inspected by a qualified technician to catch any potential electrical issues early.