Voltage running through chassis?

[GR_TVR]

Hi,

Just had an odd experience, my ear touched a brake disc whilst I was working on the car and I felt a tingle - hooking up my multimeter I noticed that there is a voltage of around 0.3V to a couple of the brake discs and so I assume the chassis as well.

First question - is this normal?
Second question - what could cause this?

I have had the starter motor off today so if it's not normal it could be something with that I suppose.
I've just remembered it's currently got a battery charger hooked up as well, if that makes any difference!

Thanks

[Steve_D]

When you did your test what points did you test between?
The disc to what else.

Steve

[GR_TVR]

Steve_D said:

When you did your test what points did you test between?
The disc to what else.

Steve

I did the disc to a metal ground on a nearby fridge.

[Steve_D]

In that case I would say it was just static.

Steve

[GR_TVR]

Would the static be a constant? It was consistently 0.3V over time.

[Alpha Omega]

GR_TVR said:

Would the static be a constant? It was consistently 0.3V over time.

I could post you my opinion on this but I am not going to, I can't possibly discuss something that for all I know could be life threatening
If you are unsure about how you received an electric shock from your vehicle you need to speak to an electrical company and it is very likely that they will suggest that you have your households main earth checked
A forum is no place to be asking about this. speak to a professional

[GR_TVR]

Interesting view. Personally I'd like to know why you recommend this and why you think they'd want to check the house earth?

For what it's worth, I've just turned off the battery charger and the voltage disappeared, so it's obviously linked to that. I'll check connections etc tomorrow if I get a chance.

[cptsideways]

Have just helped a neighbour diagnose his tipper truck not working without a lot of smoke & sparks from a grounding brake line.

After much head scratching & testing with + coming through the chassis.


It was a bad earth line to the chassis in the end

[tofts]

He could be right BUT, It comes down to 1 question, does your main household fuse board have RCDs?

If you do, then your problem is most likely static.

I nearly wrote a huge paragraph as to why but its just too much for a forum!

[GR_TVR]

tofts said:

He could be right BUT, It comes down to 1 question, does your main household fuse board have RCDs?

If you do, then your problem is most likely static.

I nearly wrote a huge paragraph as to why but its just too much for a forum!

Fair enough!
Yes, it has RCDs - the house is less than 20 years old so the wiring should be ok. I'm having an extension starting soon with a fair bit of electrical work so suppose things will get checked then.

Thanks

[Alpha Omega]

I will never forget what happened at Newbury Racecourse several years ago, many people including myself didn't think this possible
http://www.newburytoday.co.uk/news/news/420/tests-...

[Rockettvr]

Hi
Its difficult to diagnose your problem accurately on the information given but here's a few pointers
0.3 v is not going to be enough voltage to give you a shock - as you mention it looks to be a product of having your battery charger connected- so the shock you received is most likely (but not definately) from static electricity . The connections to your battery from the charger SHOULD be putting out around 14v d.c. - easily checked with a multimeter
Mains voltage shouldn't be present anywhere - check all leads (power off) for damage
As mentioned above any power outside or in the garage MUST be RCD protected Either by an rcd in the consumer unit(fuseboard) or a plug in "power breaker" rcd in the socket outlet you're using
If in any doubt turn the power off unplug and consult a qualified electrician

As a note on rcds - many people think that an rcd will stop you getting a shock - it wont , but it will limit the shock to a non - lethal level -30milliAmps but it still bloody hurts

[bobfather]

It is current that gives you a shock. You only need minute voltage to carry that current

[Loubaruch]

bobfather said:

It is current that gives you a shock. You only need minute voltage to carry that current

But under normal conditions the human body has quite a high resistance so you need considerably more than 0.3 volt to give you any sort of shock.

If you do not believe me grab hold of the leads of a multimeter on ohms range and see the result.

As the charger is causing the problem I would suggest that due to the switching regulator inside ( transformers tend not to be used as they are bulky and expensive) there is some leakage to earth, not an uncommon occurrence with switching regulators.

Depending how you measured the 0.3 volt it could actually be considerably more than this but in very short spikes, so a normal meter would average it to 0.3 volts but it could possibly be 50 volts or so for a very short spike but zero for most of the alternating cycle.

Static I do not think so!

As AO says worth getting someone competent to check things especially your charger.

[blitzracing]

You say its on a charger? Quite simply the chargers -ve connection may not be connected to the earth wire that connects it to the mains, so you end up with a small voltage difference. Modern switch mode chargers dont have the great big earth planes of the traditional type of battery charger with a transformer, and don't even have an earth wire, as the input to the output should be completely separately isolated. In your case there must be some leakage in the battery charger between the input and output to allow any current flow at all that you can feel. And before you all jump around saying that you will die- the Americans run 115 volts as this is deemed a shock the human body can take without death- I think that's around 15ma across the heart before it stops, so you are quite safe, just get a new charger.

[Alpha Omega]

It's good to witness so many sensible posts from the majority here, this proves how good the TVR forum is, there are many posters that don't jump to conclusions about an unknown but do give good advice

[GR_TVR]

Thanks for all the replies/info.

Update to this - I contacted Ctek who make the charger (which is only a month old) about this issue, they replied to say yes, it is leakage, and it is perfectly normal and acceptable...

[Bassfiendnoideawhathp]

Absolutely ... anything that isn't directly earthed will 'float' to some degree or other.

For example my work MacBook Pro has a 'tingle' when you run your fingers over its chassis as does my iPad Mini (but only when they're plugged in on the charger) - of course the Apple Fanbois would just say that's the excitement of touching an Apple product.

You'd be surprised at the amount of 'float' that is legally allowed on any surface of a product but it has to be maintained at a safe current too ... the limits do seem quite high and for some people can be regarded as giving a frightening jolt.

I know this as the company I work for make a double insulated product that has an aluminium chassis and we do sometimes get phone calls from people complaining of exactly this and we have to assure them that it's safe... 0.3v is nothing I assure you. :-)

Phil

[QBee]

Bassfiendnoideawhathp said:

Absolutely ... anything that isn't directly earthed will 'float' to some degree or other.

For example my work MacBook Pro has a 'tingle' when you run your fingers over its chassis as does my iPad Mini (but only when they're plugged in on the charger) - of course the Apple Fanbois would just say that's the excitement of touching an Apple product.

You'd be surprised at the amount of 'float' that is legally allowed on any surface of a product but it has to be maintained at a safe current too ... the limits do seem quite high and for some people can be regarded as giving a frightening jolt.

I know this as the company I work for make a double insulated product that has an aluminium chassis and we do sometimes get phone calls from people complaining of exactly this and we have to assure them that it's safe... 0.3v is nothing I assure you. :-)

Phil

I used to hear laydees say that they got a similar tingle when I ran my fingers over their chassis, but I am married now.....

Edited by QBee on Friday 2nd June 20:17

[Alpha Omega]

Shocking