My car keeps shocking me! - Page 1
Forum section: electronics / general

author: edy
author_rank: Super Contributor
timestamp: June 14, 2018, 06:34:51 pm
content: Hi folks,I'm not sure what it is, maybe the weather, my clothing, my dry skin, something with my car, but lately I keep getting these massive shocks every time I am getting out after an even relatively short drive. I would like to know why this is happening and what options I have to eliminate this very annoying phenomenon from happening!As far as understanding what is happening, I'm trying to figure out the system here.... We have car, air, seat, ground and me. Somehow we are ending up at different potentials during the drive. If it is a problem of me and the seat, then I am basically losing (or gaining) electrons from the seat and as soon as I touch the car (a large reservoir of free electrons) I get zapped. Then whether or not I ground the car with a static strip, it won't help. If somehow the frame of the car is being charged by the air, then when I ground the car through myself, I conduct to ground and neutralize the car frame again. In that case, the static strip will help. I'd like to figure out what is going on.Right now when I get out of the car I use a key (without a chip) to touch the side of my door and see a huge spark fly across the gap. Then I can safely close my door. I have LEATHER seats, and I wear shoes with RUBBER SOLES. Could it be my jacket (POLYESTER)? My tires are regular standard ones for a Honda CR-V.I can install a static strip to my car chassis and see if that helps, but if it is NOT a problem with the car but with me and the seat, then I heard that won't help and I don't want to waste money on it (as mentioned before). So meanwhile can I just wrap a copper wire around my rear tow hook and have it drag on the ground behind the car? Is there some other way I can test what is causing the static discharge? Or should I try rolling down the window and touching the metal of the car while I'm still sitting in my chair and seeing if that discharges me? I want to isolate the issue so I can figure out a solution!ADDED AFTER POSTING:https://www.school-for-champions.com/science/static_materials.htm#.WyK182NKjeQSeems like leather and polyester don't make a good match... I have a suspicion it's not the car, a static strip therefore won't help. It's me and the seat and the seat gives me back the electrons through the car metal when I touch it, whether I am still sitting in the car or not, or whether I touch a door-knob or the next sufficiently grounded or conductive large metal object I find, I will get zapped. I need static strips on my shoes, not on my car!

author: CJay
author_rank: Super Contributor
timestamp: June 14, 2018, 07:42:38 pm
content: Simple trick, get into the habit of grabbing and holding the door pillar or A pillar before you get out of the car then swing yourself out and put your feet on the ground while still holding the bit of the car you grabbed.Static charge gone.

author: jmelson
author_rank: Super Contributor
timestamp: June 14, 2018, 07:46:43 pm
content: It is not accumulating while you drive. It is when you slide your rear end across the seat just before getting up.If you keep a hand on something metal (hard to find any exposed metal on cars these days, though) it will prevent the charge from accumulating.Well, of course, it could be your tires do not have enough carbon dust in them to bleed off the charge, but that would give you the zap when your feet touch the ground.Yes, the polyester jacket is DEFINITELY part of the problem, those things develop triboelectricity like crazy!Jon

author: tautech
author_rank: Super Contributor
timestamp: June 14, 2018, 08:43:37 pm
content: It's to do with the % of carbon in the rubber of your tires. Some tires give zero problems and this is generally a dry weather problem.A antistatic strip can mostly eliminate it but not always entirely.Some of us are more susceptible to this so my wife for example can exit the car no problems but pushes on the window to close a door so to not get shocked.Consult your tire supplier next time they're due to be replaced for a set that dissipate the static charge better.Notice when you return to your vehicle you never get shocked......because the carbon in the tires has had time to do its job.

author: Halcyon
author_rank: Unknown
timestamp: June 14, 2018, 08:45:06 pm
content: The same happens to me just getting up from my office chair wearing certain clothes. I find board shorts in combination with the seat material quite bad. I've got into the habit of grounding myself by momentarily placing my foot on the metal frame as I get up, I hear a loud crack but can't feel anything.

author: Benta
author_rank: Super Contributor
timestamp: June 14, 2018, 08:46:46 pm
content: Polyester jackets? I thought those were history after "Leisure Suit Larry"

author: Stray Electron
author_rank: Super Contributor
timestamp: June 14, 2018, 09:18:59 pm
content: Quote from: Benta on June 14, 2018, 08:46:46 pmNope, we are talking about Canada here!

author: IanB
author_rank: Super Contributor
timestamp: June 14, 2018, 09:27:30 pm
content: Quote from: CJay on June 14, 2018, 07:42:38 pmI second this advice. The spark is a difference in potential between you and the car. If you hold onto a metal part of the car while getting out and putting your feet on the ground then you and the car will be at the same potential, therefore no spark.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: June 14, 2018, 11:10:01 pm
content: I am sure it is you sliding across the car seat as you exit. The A-pillar method will work if you grab it before you move your body, which may be a difficult maneuver. Anti-static spray on the carpet combined with heel straps should do the trick, and might be a good experiment to confirm the hypothesis. You could also just hook an anti-static wrist strap to some point on the frame. Again more an experiment than something you want to do all the time.Seat covers? You can console your loss of the leather appearance by telling yourself that you are preserving the leather for resale time.

author: BillB
author_rank: Unknown
timestamp: June 14, 2018, 11:27:43 pm
content: I've got good news and bad news. The good news is that this can be easily solved by attaching yourself to a good ground while you drive...

author: lowimpedance
author_rank: Super Contributor
timestamp: June 14, 2018, 11:47:47 pm
content: Quote from: BillB on June 14, 2018, 11:27:43 pmAny suggestions on the best position to attach the 'probe' for maximum grounding effect !!

author: edy
author_rank: Super Contributor
timestamp: June 15, 2018, 12:57:50 am
content: Thanks for the suggestions! I'm still trying to understand the physics involved here.EXPERIMENT:I got into my parked car that wasn't even running, with my polyester windbreaker and rubber-soled shoes, and rubbed myself around on the seat (yes I got strange looks from passers-by). Then I tried different ways to get out of the car.1. When I rotate 90 degrees and step out of the car and touch the ground pretty much straight out of the seat, then I bring my hand (or a key) to the door frame, I get a NASTY SHOCK! Even when it zaps the key, like 1.5cm spark gap, I feel my clothing jump out for a second and my hair on ends.2. When I put my hands on the roof of the car or touch some metal part of the door, and then swing out and step on the ground, I no longer get shocked. ? What is happening here?3. When I am still sitting in the chair and put my foot outside the car on the ground, and place my key near the door frame and then lift my butt off the chair, I see no spark. That would seemingly be the same as #1 but apparently not.4. When I get out of the car like scenario #1, but instead of touching the car, I point my key to the GROUND (pavement) below me, I get a nasty shock!So the charge must be limited to the top of my body, it is not draining to ground until I touch it with my finger. Also, when I touch the car I must be grounding myself too. So if anything, using a static strip on the back of the car won't help this situation at all... I will simply discharge myself through the car to ground.All of these are reproducible. For now I will try to touch the metal part of the door when I open it from the inside, which is hard because the inside handle and everything is pretty much plastic. But if I can reach out and touch either the roof or the metal part of the door and then step out, I don't get a shock once I touch the handle again to close it.I will also put on some leather soled shoes and see if I get the same effects. Can someone explain to me what is happening exactly with the electrons and charges here?

author: IanB
author_rank: Super Contributor
timestamp: June 15, 2018, 01:28:38 am
content: It's really easy.When you swivel in the chair and twist round to get out, some charge is transferred between you and the car seat. So now, when you leave the car there is a large potential difference between you and the car. Naturally when you go to touch the car that potential difference wants to equalize and that is the spark that happens--you and the car have a big difference in voltage and the spark is the result of resetting the voltage difference back to zero.So how does touching the car while you get out help?In this case, because you are touching the car roof or door you must remain at the same potential as the car. Any charge transferred between you and the car seat immediately flows back through your hand to the car leaving no voltage behind. So now when you let go of the car there is no potential difference between you and the car, and so no spark when you later touch it.Bear in mind that the ground never has anything to do with this. The voltage difference is always between you and the car. The ground beneath your feet is just an innocent bystander.

author: Halcyon
author_rank: Unknown
timestamp: June 15, 2018, 01:38:41 am
content: I suppose you could just wrap a thin wire around the door handle which is connected to the car body (like one of the bolts holding the door).

author: sleemanj
author_rank: Super Contributor
timestamp: June 15, 2018, 01:44:18 am
content: Hold your keys, touch the the door with the key when you get out. That's what I used to do when we had a particularly static inducing vehicle

author: edy
author_rank: Super Contributor
timestamp: June 15, 2018, 02:16:20 am
content: Thanks for the explanation. I just drove somewhere and decided to put on a different pair of shoes (leather shoes although the sole was rubberized at some point because the leather got worn, we had a thin layer placed when the shoes were repaired). I tried hard as possible to "charge" myself in the seat, got out and couldn't get a spark to happen.So assuming I am charging up myself in the seat, the charge needs to equalize. According to the triboelectric series table, leather tends to give up electrons and polyester attracts it. So I become negatively charged (or at least my jacket does). Now if I touch the car while I am still sitting in the chair, why do I not get shocked? How is that different than touching the car when I separate myself from the chair and step outside the car?If I am negatively charged and the electrons want to jump back to the car (which is now positive or at least the seat is)... they won't go back if I touch the leather chair (e.g. if I get out of the car and touch the seat), but they will go back if I touch the metal frame of the car. I assume this is it is a less resistant path, or is it because the car has a huge reservoir of free electrons for which me touching it will make little difference to it overall? Same goes for when I get out and touch the ground. I must be discharging my electrons into the ground or whatever other large reservoir exists?And if I am stepping out of the car with conductive soles (or barefoot) would I not feel a zap in my feet when I touch the ground? Or is it because I am still sitting? Somehow I am managing to separate myself from the chair but not yet equalized with anything (either ground or car) because the shoes are rubber, and then if I touch the car metal or pavement I will see a huge spark through my finger or a key. Somehow still being in the chair when I either touch ground or car causes the problem to go away... That is, touch car with my hand (either door or roof) or touch the ground with my conductive feet (or hands if I reach done). Either way, in each case I am still planted in the seat when I "equalize".LET'S SEE... I THINK I FINALLY UNDERSTAND IT:If you charge a capacitor and then you short out the leads, you see a large "zap" across it. So if my polyester jacket is one side of the "capacitor" and the leather seat is the other side, if I touch the metal of the car (even not getting up from the chair) WHY would this not discharge me just the same and result in a zap too? Why do I have to then separate my butt from the chair?I imagine it like this: While I am in the chair, the electrons (even though they are in my jacket) are being attracted to the seat so they are pretty much "coating" my back. When I get away from the seat, the electrons spread out equality in my body as they are no longer attracted to the seat, they repel from each other and are trying to be as far away from each other as possible. If I touch the car, they are being repelled from each other and also I have excess number in my body, so they look for any opportunity to jump out of me into a much larger conductive free-electron source. If I touch another car, I assume the same would happen, just like touching the ground, or a large metal garbage bin, etc.Somehow getting out of the car and touching the ground with somewhat conductive shoes also releases them but either my feet are not as sensitive or the sole "bleeds" it out slowly (like using a bleed resistor to discharge a capacitor). Because it is discharged more slowly I don't feel the shock.Now if I am *still* in the seat, and I touch the metal frame of the car... I am also creating a path to the chair, yet it is not like shorting out a charged cap? Perhaps the path through the car back to the seat provides enough resistance (but not too much) to allow my electrons to flow back slowly, effectively discharging me "one side of the capacitor" to the leather chair. Now when I get out of the car, I am neutral so I no longer get zapped by the car. If my chair was on RUBBER supports in the car, would this still work? Now by touching the car it would not provide a path back to the chair... what would happen?Seems like as long as my butt is planted in the chair, it is like the "capacitor" plates are close together, I can discharge the system slowly this way by providing a resistant path through from one plate to the other (by touching the car). The minute I separate the capacitor plates (my jacket and the seat) and then touch them to anything else, the spark develops. Getting out of the car in conductive shoes perhaps is the same as touching the car while I am still in the seat... it also lets charge flow back through to the car by going through the ground and back up through the tires and into the seat. Both instances, I am still in the seat... i.e. the plates are in close proximity still when the discharge happens.Am I thinking this through properly?

author: IanB
author_rank: Super Contributor
timestamp: June 15, 2018, 02:49:03 am
content: If you think about a capacitor, if you separate the plates of a charged capacitor the voltage goes up. (V = Q/C and if C goes down V goes up.) So while you are sitting in the seat the capacitance is high and the voltage is low (= no spark). If you get out of the car you are separating the plates. The capacitance goes down, the voltage goes up, and now you get a bigger spark (ouch).

author: lordvader88
author_rank: Frequent Contributor
timestamp: June 15, 2018, 06:58:53 pm
content: I squat my fingers in a car door 1 time in the weirdest way, could have been a LOT worse. Afterwards I was like.....how did I do that

author: aju11
author_rank: Contributor
timestamp: June 19, 2018, 12:36:38 pm
content: Quote from: jmelson on June 14, 2018, 07:46:43 pmThat works for me too.I would also suggest to try out with different pairs of shoes.

author: HoracioDos
author_rank: Frequent Contributor
timestamp: June 19, 2018, 02:21:03 pm
content: I used to have the same problem with an old Renault. So I began to touch the car with the back of my hand first to make it less painful.

author: jmelson
author_rank: Super Contributor
timestamp: June 19, 2018, 08:21:11 pm
content: Quote from: edy on June 15, 2018, 02:16:20 amMost of the car interior is plastic, and a good insulator. If you touch plastic, you get no shock, but don't discharge any charge you may have. Only when you touch metal do you get a shock. Or, if you HOLD your hand on something metal WHILE shifting your body, charge will be dissipated as it develops, and no shock.So, the problem occurs when you are not grounded to anything and build up a charge, THEN touch metal and zap!Jon

author: vk6zgo
author_rank: Super Contributor
timestamp: June 20, 2018, 02:30:37 am
content: Back in the day, I had an old Holden car which was the "bottom of the line" model.This meant it lacked a few "frills", one of which was keyholes on both front doors.Normally, I unlocked the passenger side & reached over to "pop" the driver's side door, but sometimes, if I was in a hurry, I would just get in & slide across the vinyl bench seat to the driving position.I kept getting what felt like a jab from a sharp edge on my finger as I put the key in the ignition, so examined the key & key ring closely for anything sharp.Nothing there, so it was a mystery, until I slid into my car at night.The culprit showed up clearly-----a nice big static electrical spark.Just as in your case, nothing else was well enough connected to chassis to cause a spark, till I touched the ignition switch.

author: Jeroen3
author_rank: Super Contributor
timestamp: June 20, 2018, 06:02:41 am
content: My Honda also zaps me. It's the price you pay for not getting leather seats.You can buy better shoes, or use straps.Just make sure you touch the car before grabbing the petrol tank lid or gun.

author: GeorgeOfTheJungle
author_rank: Super Contributor
timestamp: June 20, 2018, 07:05:59 am
content: That happens to me with a chair I have in the garden, at night I can even see and hear the sparks. I charge myself and zap my wife with the tip of the finger hahaha then say you see? Sparks between us! (do it more than once and you'll sleep in the sofa)

author: amyk
author_rank: Super Contributor
timestamp: June 20, 2018, 11:39:29 am
content: Quote from: edy on June 15, 2018, 12:57:50 am1.5cm? That's roughly 45kV, given the standard 3kV/mm dielectric strength of air.Do you live in a very dry climate? Perhaps a humidifier would help.Interesting related article:http://web.archive.org/web/20110727191123/http://www.jci.co.uk/Carseats2.html