9
\$\begingroup\$

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
\$\endgroup\$
6
  • 1
    \$\begingroup\$ If you have cloth or vinyl seats, you can generate significant amounts of static electricity as you slide across the seat while getting in or out of the vehicle. You can purchase a spray that reduces or eliminates that problem - one brand name is "Staticide". \$\endgroup\$ Apr 18, 2015 at 11:34
  • \$\begingroup\$ Although I've never used it personally, I've also read that a light misting of a liquid fabric softener can also be effective - that would be Downy or Fleecy in North America. \$\endgroup\$ Apr 18, 2015 at 11:36
  • 1
    \$\begingroup\$ Touch a piece of "Anti static foam" in contact between you and the car. This also prevents zapping computers. \$\endgroup\$ Apr 18, 2015 at 12:40
  • \$\begingroup\$ I hold on to the frame as I'm getting out and i NEVER get zapped. Works for taking clothes out of a dryer too \$\endgroup\$
    – DerStrom8
    Apr 18, 2015 at 20:08
  • \$\begingroup\$ Rather than touching your key to the van, which could scratch the paintwork, touch the van with the back of your hand first. The greater surface area means the electric current is much less concentrated and the back of your hand is much less sensitive. \$\endgroup\$ Apr 19, 2015 at 0:44

5 Answers 5

10
\$\begingroup\$

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.

\$\endgroup\$
2
  • \$\begingroup\$ Great answer. Two questions though: why though would shoes only provide insulation until I close the door? Is it that they are actually always insulating and do not play a part in dissipating the charge when I get the shock from the vehicle? Also, why do I not get a shock while in the vehicle? Is it only because I haven't been rubbing up some charge before I've exited? \$\endgroup\$
    – Jodes
    Apr 18, 2015 at 15:38
  • \$\begingroup\$ You actually could be accumulating charges while driving if you're moving a lot, because everything around you is isolating. But you don't get a shock either because there is no chance of touching anything conductive. If the leakage is sufficient that might not build up in fact. When you get out, you get charged quickly, and immediately after you short yourself to the chassis of the car. The shoes are always insulating you from the ground, you just discharge via a different path: the fingers. \$\endgroup\$ Apr 18, 2015 at 15:44
1
\$\begingroup\$

Have you tried to simply spray your seat with anti-static spray? There are also much more effective industrial conductive sprays (some of those are transparent) if a simple anti-static is not enough.

Note that many consumer-grade anti-static products simply absorb humidity from the air (and water makes fabric conductive), so they won't work if the air is dry. Incidentally, an air moisturizer could help.

Another idea is to try an air ionizer (ionized air is itself conductive and dissipates the static charges), although I don't know how effective car ionizers are. This method is used to dissipate charges in labs where conductive sprays would interfere with the experiments.

This would eliminate the problem at it source, as you're definitely get those charges from your seat.

\$\endgroup\$
0
\$\begingroup\$

Touch the metal of the car before touching the ground with your shoes.

This will make you ground through your shoes (which you won't notice) instead of through your finger.

\$\endgroup\$
0
\$\begingroup\$

The method I use is to place your finger on the metal while you are in the seat and leave it on as you get out. When your clothes rub on the seat, electrons are rubbed off one onto the other, so they become charged. The seat and your clothes, and you, form plates of 2 capacitors in series. While the plates are close, the charges attract each other, increasing the capacitance (charge storing capacity), making the voltage (pressure) low. When you move away, the capacitance decreases, like a piston decreasing the volume of a cylinder, increasing the pressure (voltage), which is coupled to you from your clothes through the capacitor formed by you and your clothes. If you place your finger on the metal while in the seat, the voltage is too low to zap you. As you get out and the voltage on your clothes increases the charge coupled to you just leaks away through your finger.

\$\endgroup\$
0
\$\begingroup\$

Besides the obvious solutions mentioned here, I want to mention a very generic method that works all the time in various situations throughout the day.

You can end up charged in a variety of situations (carpets, chairs, shoes etc.). You then get a painful zap in the following situation:

  • you retain a large static charge
  • there is a well conductive point nearby into which you can discharge
  • all the charge leaves your body fast and through a tiny point leading to a high current density

The last bullet happens if you approach the metal surface slowly and the intermediate air has time to breakdown forming an arc.

You can universally avoid the last "ingredient" by touching the discharge surface very fast. This will create a much larger contact area and will render to local current density too low to feel.

A door handle will never zap you if you slap it before it can 😉.

\$\endgroup\$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.