Have you ever left your car parked for a few days, only to return to a dead battery? If so, you’ve likely experienced a “phantom” or “parasitic” battery draw.
Like a ghost lurking in the background, it slowly drains the life from your vehicle’s battery. But what exactly is a phantom or parasitic draw, and how can you fix it?
What is Phantom or Parasitic Draw?
A phantom or parasitic draw occurs when electrical devices or systems in your car consume your battery’s power, even when the vehicle is turned off. While some battery drain is expected (like keeping your car’s clock or alarm system running), excessive electrical draw can lead to frequent dead batteries and other electrical issues.
This usually happens when items like the radio, lights, or onboard computers fail to shut down properly.
So, how can you tell if you have a phantom or parasitic draw?
Signs You Have a Parasitic Battery Draw
While spotting a parasitic battery draw can seem impossible, the symptoms are obvious. They include the following:
Frequent Dead Battery
If your car’s battery is constantly drained, something is likely drawing power when it shouldn’t. If you regularly recharge your battery or don’t use the vehicle often but still find the battery dead, you may have a parasitic draw.
Dim or Flickering Lights
Another indication that your car has a parasitic draw is if its interior lights flicker or its headlights seem unusually dim. This is due to the car’s unhealthy battery.
Unexplained Electrical Glitches
Erratic behaviour from your car’s electronic systems, such as malfunctioning accessories or inconsistent performance from built-in devices, can also signify a parasitic draw.
Now that we know the symptoms, what could be causing these problems?
Common Causes of Phantom Battery Drain
There are a few common causes for a phantom or parasitic draw. These include the following:
Faulty Wiring or Grounding
A poorly grounded or faulty wire can cause a phantom battery draw. If wiring is done incorrectly, electricity can flow where it shouldn’t, slowly draining your vehicle’s battery.
Stuck Relays or Switches
Your vehicle has loads of switches and relays. In most vehicles, relays are responsible for lower amp circuits to switch on and off higher amp circuits. If you simply wire in your car’s headlights to a simple switch, it would burn out the switch, posing a fire hazard.
But if these relays and switches fail to turn off completely, they leave an electrical circuit active, drawing power and eventually draining your battery.
Old or Defective Battery
All batteries lose their ability to hold a charge over time. An older and weaker battery is also more prone to a parasitic drain.
We’d recommend changing your older battery to solve the issue.
Aftermarket Accessories
For those looking to bring their older rides into the 21st century, you may be tempted to add new aftermarket accessories.
However, if incorrectly installed or defective, electronics like car alarms, radios, or GPS units can pull more power than expected, even when the car is off.
Also, if you’ve installed more devices, like a dashboard camera, and forget to turn them off, they can drain your vehicle’s battery.
Glitchy Control Modules
Many modern vehicles have a million and one features. These new features must be fitted with various control modules (computers). If these modules malfunction and fail to enter “sleep mode” when the vehicle is off, these systems will drain the battery.
How to Detect a Parasitic Draw
If you’re uncertain about performing voltage checks, ask one of our helpful stockists for assistance. But if you’re competent enough, here are a few methods to detect it as a parasitic draw.
Check Battery Voltage
You can use a multimeter to check your car’s battery voltage and confirm if something is draining it. When fully charged, a healthy battery should measure between 12.4 and 12.7 volts. Anything lower might indicate a parasitic draw or a bad battery.
Set your multimeter to measure amperage (current) to test for a parasitic draw. Disconnect the car battery’s negative terminal, then place the multimeter in series between the negative terminal and the battery cable. You likely have a phantom draw if the reading is higher than 50 milliamps.
To pinpoint the component causing the draw, pull fuses one by one while monitoring the multimeter. When the parasitic draw drops, you’ve likely found the culprit.
How to Fix a Parasitic Draw
When you’ve narrowed down what component in your car is the issue, you will want to do the following:
Step 1: Check for Faulty Wiring
Inspect the wiring for any signs of damage, loose connections, or frayed wires. If nothing is visible, proceed to the next step.
Step 2: Inspect Relays and Switches
As mentioned, faulty switches or relays stuck in the “on” position commonly cause a parasitic draw.
Replacing these faulty relays or switches can stop the drain.
Step 3: Uninstall Problematic Accessories
If you’ve discovered that your aftermarket accessory has caused the parasitic draw, it’s best to inspect the wiring to see if it’s done correctly or to uninstall it if the product is faulty.
Step 4: Upgrade or Replace the Battery
Once you’ve fixed the parasitic draw, consider replacing the battery, especially if it’s nearing the end of its life. A higher-quality SABAT battery will handle the workload better and give you more time to address future issues.
Preventing Future Battery Drain
To prevent parasitic draw in the future, always turn off all electrical devices when they’re not in use, including:
- Lights
- Radio
- Other accessories
Also, perform regular amp draw tests. If you plan to leave your car parked for an extended period, consider plugging the battery into a smart trickle charger. Proper battery maintenance is critical to avoiding future issues.
If you have any other questions, you can talk to us or a specialist at one of our many stockists.