Does Leaving Chargers Plugged in Increase the Risk of Fire?
By Lakshmi Santhosh
Updated April 25, 2017
People often leave their cell phones and laptops chargers plugged in to the wall at all times for the sake of convenience, even when they are not charging or using the equipment. While electrical safety has increased dramatically, this could still turn out be dangerous. But there are easy ways to prevent any catastrophes.
Is There a Risk?
Chargers, whether for laptops, cell phones or tablets, have become a necessity of modern life. The convenience of leaving devices plugged in has made it a common practice. These chargers are constantly drawing power, though not as much as they would if they were turned on. It could lead to a risk of fire either through heat buildup or a short circuit.
Why Do Chargers Pull Power?
The risk results from the way chargers extract their power. Chargers convert alternating current, or AC, to direct current, or DC, from the outlet using transformer circuits. These consist of two coils, one small and one large that loop around and use an electromagnetic field to influence each other. When you unplug your electronic device from the charger, this breaks the circuit on the smaller coil, but the larger coil continues to move electrons. This causes a little bit of power to leak into the charger even if it is not connected to any device. Power can also be drawn out if there is an LED present in the charger, as this causes more resistance.
What Makes This Dangerous?
While pulling power does not cause an immediate danger, the side effects could be enough to cause a spark. The transformer circuit releases heat when converting AC to DC. The heat can slowly accumulate and cause nearby fabric or wood to ignite. Such an incident could be even more likely when a device is actually connected to a charger, as an unconnected charger will not accumulate enough heat for this to happen. That is why it’s safer to charge your devices on cool surfaces and away from flammable objects.
However, chargers not connected to any devices can still pull in power. If there happens to be enough water or moisture in the air, it can short-circuit the transformer. During a short circuit, abnormal connections within the circuit cause an excessive amount of current to pass through the charger, which overheats the circuits and could potentially start a fire.
How Do I Avoid This?
The best way to avoid possible short-circuits is to use a power strip, especially if you do not plan to unplug your charger between uses. While the obvious advantage of a multi-plug power strip is that you use one outlet for multiple devices, power strips also work as surge protectors and turn off when not in use. As an added precaution for short circuits you should still keep chargers away from moisture.
Lakshmi has a Masters in biotechnology from the University of Pennsylvania and Bachelor's in economics from UC Berkeley. She has written about science for "Future Medicine," RegBlog.org and "ACP Internist."