Bluetooth OBD2 scanners are increasingly popular among car owners for their ability to provide real-time diagnostics and vehicle data. These handy devices plug into your car’s OBD2 port, offering insights into engine performance and potential issues. A common concern for users is whether it’s safe to leave these scanners plugged in all the time, or if it could lead to problems. Specifically, Are Bluetooth Obd2 Scanners Safe To Leave Plugged In when the car is not running?
Understanding the OBD2 Port and Power Draw
To answer this question, it’s essential to understand how the OBD2 port is powered. According to international standards, and as seen in vehicles like the BMW E46 which utilizes the ISO 9141-2 standard, pin 16 of the OBD2 port is designed to be permanently live. This means it continuously provides power, even when the car’s ignition is switched off. Consequently, any device plugged into this port, including Bluetooth OBD2 scanners, will inherently draw current.
Even when seemingly inactive or in a “sleep mode,” a Bluetooth OBD2 scanner remains powered and consumes a small amount of electrical current. While this draw is typically minimal, often around 10mA, it is still a continuous drain on your car’s battery.
The Impact of Parasitic Drain on Your Car Battery
This constant, albeit small, power consumption is known as parasitic drain. For vehicles used daily or very frequently, the impact of a 10mA drain from an OBD2 scanner is usually negligible. The alternator replenishes the battery charge during regular driving, offsetting this minor drain. In such cases, you might not notice any negative effects from leaving the scanner plugged in.
However, the situation changes for vehicles that are not driven regularly. If your car sits idle for extended periods, such as weeks or even a month, the cumulative effect of even a small parasitic drain can become significant. A constant 10mA drain, while seemingly insignificant, can gradually deplete the battery’s charge. This could lead to a noticeably shorter battery lifespan and, in more extreme cases, a flat battery, especially in colder climates where battery performance is already reduced. For instance, if your car typically experiences a 30mA sleep consumption, adding another 10mA from a plugged-in scanner increases the total to 40mA. While this might seem small, over weeks of inactivity, it can reduce the battery’s effective lifespan.
Smart Scanners and Voltage Detection
Many modern Bluetooth OBD2 scanners are designed with power-saving features. Some utilize battery voltage sensing to detect when the car is running. These devices often go into a low-power “sleep mode” when they sense the voltage drop associated with the engine being off (typically below 13.2v). This sleep mode reduces their power consumption but doesn’t eliminate it entirely. They remain connected and monitor the voltage, ready to “wake up” when the car is started again. Even in sleep mode, these scanners still draw a small amount of current to maintain this monitoring capability.
Best Practices: When to Unplug Your OBD2 Scanner
While the convenience of leaving a Bluetooth OBD2 scanner plugged in is undeniable, it’s generally advisable to unplug it, particularly if you do not drive your car frequently. For daily drivers, the risk is minimal. However, for vehicles used only a few times a week or less, unplugging the scanner when not actively in use is a prudent measure to prevent unnecessary battery drain and prolong battery life. This simple habit ensures that your battery maintains its charge optimally, especially during periods of prolonged inactivity, giving you peace of mind and avoiding potential starting issues.
