Electronic – Avoiding static shocks from vehicles


I don't entirely understand static electricity; particularly how it seems to flow through rubber shoes and paint, but seemingly not rubber tyres or car seats.

I am tired of getting shocks from my van.

I've read that those anti-static strips for vehicles that drag on the ground were banned from being marketed since they don't actually work. I also read that the strips are less effective than the tyres depositing charge as they roll on the road.

I've read that the best methods for avoiding the shocks are to either hold onto the frame of your car as you're getting out, or alternatively, once you're out of your car, before touching the door to close it, hold the metal of your key and tap it with the end. I believe I've had some success with these, but not all the time.

What different ways and where might the static electricity be building up? Why do/don't the above methods work? And what can be done?

Some ideas:

  • Cover the seat with anti-static [something]
  • Try an anti-static strip anyway

Best Answer

In most cars, you are isolated from the chassis when you're driving: everything is plastic, leather or textile. When you get out of your car, friction can rip off charges from the electrically neutral environment (this is called tribocharging) such that the potential difference between you and the ground increases drastically. When you set foot on the ground, your shoes are normally isolating you sufficiently for you to retain that charge.

On the other hand, the chassis is pretty much at ground potential: yes, it is isolated from ground by the tyres, but there is still electrical leakage through the tyres so over time, any difference of potential leaks out. Therefore, when you touch the door to close it, you are effectively triggering an uncontrolled discharge to ground. As you guessed, the so-called antistatic strips will not help you because the chassis is already pretty much at ground potential.

This is the same thing as the protection against electrostatic discharges in chips. Standard practice is to never use isolating materials (which prevent equipotentiality) nor conductive materials (which do not control discharges) for your environment, but dissipative materials instead. Now, you are not going to redo the interior of your car with dissipative mats, but you can still control the discharge the way you prefer.

Personally I would place a small metal plate in the door near the handle connected to the chassis via a 100k-1MOhm resistor (which makes it a dissipative material), or even hack the inside handle to make it nicer. Touch it after you are finished rubbing yourself against the seat and before you close the door and you should be fine.