12V "Shocks"

I agree.

Phil

A scientifically qualified educator once assured me that the 'average' human only needs 100mA passing through the chest cavity to experience a life threatening episode.... the voltage required to push that small amount of energy through varies with the circumstances of course ......but I guess in this situation, the worst case scenario could easily present itself one day.

OK lets talk reality here “12 volts can kill”
Yes possibly if you penetrated the chest and connected it directly to the heart.

12 volts can kill and there are recorded cases of people drowing, due to being paralised by 12 volts from inadequately insulated underwater pool lights.

There was a major to do over it back in the mid 80's with a couple of deaths.
One situation where one person discovered another helpless at the bottom of the pool, jumped in to rescue and drowned also.

While not 12 volts but relativly low DC voltages when applied to the chest can paralyse breathing, applied to the head can casue convulsion or similar. Likewise relativly low voltages can cause uncontrollable muscle spasims.

We are not talking the relativly poor contact quality that can kill with 240v, but where there is very good contact quality, such as when water is inviolved very low DC voltages can disable and kill humans.

cheers

There are a number of accidental deaths reported each year caused by arc welding machines with an output of around 50 volts AC (AC being more dangerous to the heart) or 120 volts DC. This is common knowledge but I haven’t seen any credible reports on deaths by 12 volt DC.
It may be possible if I placed a 12 volt electrode into my chest near my heart and another into my back, both located beneath the skin and into conductive flesh.
I would have a better chance of winning Tatts Lotto than being electrocuted by 12 volt DC.

Just because you haven't heard of it, it don't mean it don't happen.

you are also failing to understand the mechanism by which death occurs.

It is very unlikely that 12 volts DC will stop your heart.

Death or injury occurs by a more round about means. such as muscular paralysis, making the victim weak or helpless, respiratory paralysis, the victim can not control breathing or struggles to breathe.

Let me tell you when a toad hops into my rust removal by electrolisis bath...running 12 volts.....it does not hop out.

The way DC acts on the body is very different to that of AC, and one of the very good reasons why our electrical grid runs AC rather than the DC that Thomas Eddison advocated.

The effect of DC current on muscles is very well understood and in fact one of the very first observed effects of electricity.

There is a very common conception that 12 volts DC is perfectly safe and can't harm you.
In most situations where we encounter 12V DC and other voltages below 32 volts that is pretty much the case.

But there are a number of very limited situations where very low volatge DC can kill very effectivly......and it ain't quick like it can be with higher voltage at AC.

Being perfectly conciuos but perfectly helpless in the water is not a nice way to go.

If you havn't heard of this Ya musn't have been listening in high school science.
It was certainly covererd when I went to trade school and in several traning courses since.

cheers

Yep, you can get electrocuted at 12v, and you can get hit by a meteor too!

At 12V your end point to end point resistance VIA the heart would have to be less than about 100 ohms. Go wet your hands in salty water and measure the resistance. I think you will find it is well over about 1500 ohms.

The reason the electricity supply is AC has nothing to do with electrocution. That's a new one. AC, DC or cross dressing, 240V can kill you. It is AC for one reason. It can be transformed to higher voltages for transmission with less resistive loss, and lower voltages for end use.

Humans aren't toads, not really a useful comparison.

Again another who fails to understand how very low voltage DC kills.

I'll say it again, it aint going to stop ya heart...the whole heart thing is nothing to do with it.

Its all to do with muscular paralysis....and there are varying stages, partial control of muscles can be lost at quite low current flows.

And another one who either did not go to trade school or was not listening.

There are several reasons why we dont use DC for reticulated power.......well not any more....many of our major cities had DC power grids in the early days....transmission loss and the ability to use transformers in only one of them

One of the reasons we don't used DC is because if you get hung up on it your muscles contract and ya cant let go, they cant even prize you off.....there is very much a tendancy that the contracting muscles will pull you into the power source making matters very much worse.

Another reason we don't distribute DC is because of the difficulty in switching it......a typical switch rated at 240v AC 5 amps will generally be rated at 10 or 20 times less voltage for DC.
because DC will draw a long arc between contacts, AC we get 100 zero crossing points every second where the voltage across the switch drops to zero and the arc goes out..

another minor issue is with water heating devices......DC in ya jug and the metal parts wont last long, it produces explosive gasses and leaves a funny taste in the water.
For the same reason corrosion is a massive problem in DC reticulation systems.

Eddison was very much an advocate of DC for power grids, and he had various methods of over comming some of the problems.

BUT at the time DC was considered far more dangerous than AC, with good reason.

The general public and many of those who worked in the early days of electricity where $#@t scared of DC for very good reasons.

110 volts DC, with huge current capacity...hell we weld at 50 volts and limit the current.

The abandonment of DC reticulation by far predated the use of high voltage reticulation.


As far as muscular function is concerned toads work just the same as humans.....with one very imporatant difference...toads are amphibians...they live in the water..... and if you can drown a toad you are doing very well.

cheers

Where do you get this stuff?

Grab two 240V AC wires and get back to me if you can let go.

Dennis...... arc welders and mig welders are DC, not AC. most metal weld better with DC..... hence why most welders are DC, aluminium welds better with AC.

DC is far more dangerous than AC.

Boobook mate where do I get this stuff.......from proper electrical training.

AC will cause various muscular reactions, but nowhere near as violent or as rigid as would be if it was the same voltage in DC.

If dealing with DC, the industry standard insulated crook in the switchboard rescue kit would be nearly useless, becuase the victim would have all their muscles clenched beyond normal human strength thus they would be nearly impossible to free from thehazard.
In fact all our current procedures for electrical rescue would not work, because of the massive muscle clenching that DC causes.

Much of the reason that you can not let go of AC sources is due to your inability to control the muscles because the AC passing thru your body makes the small electrical signals the human body works on unable to be heard by the muscles.

As per the training, in many cases the victim can be knocked or pulled free with the insulated crook, or the gloves in the rescue kit.
As I say if it was DC there would be no hope.



On the matter of welders.
Most of the older style transformer bassed arc welders where most definitely AC.
MIG and TIG rely on being DC.
The higher end arc welders and almost all modern electronic welders are DC.

They are DC because DC holds a far more stable arc than AC can.

The reason we use DC for welding is exactly what make DC so dangerous.

cheers

Hi Olcoolone
You surprise me

An arc welder is a term for a welding machine that strikes an arc between the rod or wire feed and the base metal. The most common I’ve seen are the AC stick welders (excluding the old resistance pilot arc welders).

There are a lot of DC welders in use especially the Mig and Tig type - as to what is the most common who knows, who cares.

Volt for volt, AC is more dangerous to the heart than DC – only common sense, if you look at the regulations governing their output voltage.

Hi
Lots of intersting comment,so here are mine
[1 Yes, you often can feel a very slight tingle from dc which has a ripple component as most chargers have
[2]Depending on the charger IT may put out quite high voltage pulses for such actions as desuplhation
[3]Many also have a quite rapid PWM means of maintaining the float stage
[4] 12V pure DC kill I do not think so,
BUt if DC with a high ripple content was flowing through a pole then a person in that pool may end up in trouble.

[5]Now when it comes to the accepted normally safe voltages, the Standards take this into consideration when they dtermine what constitutes "LOW VOLTAGE"

LOw voltage work is generally required to be performed by licensed electricians Because THAt is where the dangers really start
the Standards determine LOW voltage as being:[in the areas most would be concerned
[a] 'AC voltages in excess 50V but not exceeding 1000V
[b]RIPPLE FREE DC voltages in excess of 120V but less than 1500DC



NOTE THE DC VOLTAGES ARE HIGHER THAN THE AC VOLTAGES

THE STANDARDS & STATE REGULATIONS consider that up 120V RIPPLE FREE DC does not require regulatory control
It is SAFER than 50V AC
However ANY DC in which the ripple peaks exceed 50V move the DC into the LOW voltage REGULATED requirements


PeterQ

HI
Just one other point IF a tingle is fealt .it should be invesigated
Even though double insulated equipment has to pass strigent test requirement to get Aus approval ,every unit made is not tested .
There have been numerous recall of DOUBLE insulated eqiuipment due to manufacturing faults
Then of course we have Ebay !!! much of which does not have AUS approval !!
further to above post Under the right /wrog circumstances [EXTRA LOW VOLTAGE CAN KILL OR DO SERIOUS HARM
I have personally witnessed THAT with 32V AC lightiing[serous long term harm & !!the person was lucky to have survived
i
To the OP
If the tingle is from positive to negative ,[pos to chassis/frame] I would suggest it just the charger design
BUT any sign of a tingle from chassis or battery[ neg or pos] to mother earth ,then ACT NOW HAVE IT CHECKED


PeterQ

HI
Some questions of the OP
Is the camper wired for 240v ??
if so does it have a RCD [safety switch]??
Is the charger plugged into mains supply direct, or into the camper 240V wiring??
IF the charger is plugged into the CAMPER 240V ther may be MORE than one problem!
[1] The camper/s mains earthing may have a problem
[2]And you may have a charger that requires attention


PeterQ

Dennis.... yes CHEAP arc welders of today are AC and are aimed at the DIYer who doesn't know better (and wonder why their welds look like.... bad), these days and for the last 15-20 years most better quality arc welders are DC.

Tig welders come in either DC only and AC/DC, the AC/DC type are used for aluminium and are 2-3 times the price of a straight DC version.

The only real advantage a straight AC arc welder has is if you have something you don't want to become magnetised from friction like hay bailers.

Most welder will work in the 20-50v range with current up to 400amps.

Many old (2 ton and above) arc welders were straight AC.

DC offers the advantage of much easier starts with smoother flow, the arc doesn't drop out and cause rods to stick, less spatter and the welds look neater and it a hell of a lot easier doing vertical up and overhead welds.

DC+ to rod is ideal for thinner materials and general purpose and changing to a DC- rod gives about 15% more grunt for thicker materials.

To do the same with a tig or mig welder all you do is alter the gas mixture.

Hi Olcoolone

I said I was surprised that you stated;
“arc welders and mig welders are DC, not AC” and “DC is far more dangerous than AC”.
I didn’t get into a discussion on the merits of the different types of welders – that is way off thread.

I refer you to the Australian Standard which shows Allowable Voltages –Welding AS 1674.2 –2007

See also oldtracks explanation on the safety levels of AC and DC voltages

As I have stated elsewhere, the vast majority of the electrical standards work worldwide is written by and for the main stream electrical industry who have a very narrow AC centric view and experience of electricity indeed.

Those voltage thresholds are almost totally framed around stopping the heart and mostly from dry, stand up and touch with the hand contexts.

There are a whole range of risks that come into play when the context is different.

Introduce quantities of water and those thresholds listed in the standards are completely irrelevent because death can occur at very very much lower voltages.

Those listed voltage thresholds also do not account for a whole string of other well known electrical hazards......even when you restrict thinking to dry, stand up and touch with the hand situations.

Those thresholds also only account for single cause death and injury.....effects directly caused by the electricity with no other factors considered.

There is little or no consideration of chain of conequence or complicated situations.

The thresholds in the standards are for regulatory purposes and most certainly do not and can not represent a comprehensive risk assessment.

cheers

Hi Bantam,
I’ve come to the conclusion that we live on different planets.

I am having a shocking time with this thread. Hope old mate tracks where he is getting the leakage from.

I am at the point of dropping a big 12v battery on my head so there proof, 12 volts can kill.

Well Rockape, it is well known that heavy 12V batteries can kill you when they drop on your head, and of course they are DC. But not many people know that an AC Alternator can also kill in the right circumstances.

Even a small alternator can kill if conditions are right.

Many people think the minimum size is 5 kg, but in theory at least, even a 1kg alternator can kill. If the Alternator is still spinning when it hits you, you could also get electrocuted, so technically the hit on the head would not be the cause of death, especially if the electrocution is instant. Please refer to the top of the thread and read all the way down for details of circumstances of death by electrocution.

Ok I electrocuted myself to stop me typing. Luckily it was only 12 VDC, or it could have been serious.

Boobook,
no way am I putting myself through the pain of reading it again. LOL.

I shall (Mandatory), go and watch the closing stages of Bathurst, and in doing so hope I don't come in contact with the terminals of the aaa batteries in the remote.

A very interesting discussion taking me back to the days so AS 3000 theory. In answer to the question I saw, the trailer is not wired for 240v and does not have any outlets wired into it. The charger which is an extremely reputable brand is quit new and is powered via an extension lead.
Tim

And I failed to mention, the tingle is felt when touching the box, not the positive terminal, there is obviously some type of residual voltage which has a higher potential then earth.

Hi
In THAT case is the charger
[a]a Class1 device or
[b] a Class 2 ??

Does it have a 3pin or a 2pin plug??

[c] IF a Class 1 is the charger metal body contacting the metal frame of the camper??

if the answer to [a] &[c]is "yes" it is quite possible that the tingle is due to stray EARTH currents
i

PeterQ

I'm sorry Dennis..... if you have taken the time to read Australian Standard AS 1674.2 –2007 and you have no active involvement other than for personal use I suggest you seek URGENT help.

Wanttobes who read technical information for no reason always seems to have me shaking my head in disbelief.

Can I ask, why did you read that particular standards or do you read all the standards for fun?

Further more yes I know I went overboard giving reasons why one welder is better than the other....... just the same as you have done about welders giving off shocks........ the thread was about battery charging...... now what's that saying about "the kettle calling the pot black". Practice what you preach Dennis.

Hi Olcoolone,
Cool down old fella
Before I retired I had to know various Australian standards like these.
But I am not going to get into a debate over the internet about who is more qualified.
It’s a pointless exercise – you could have failed kindergarten for all I know.

One thing we know about any type of standard is that they NEVER represent a complete understanding of the matter.

They are written for regulatory purposes and without exception only deal with a very narrow view of the situation.

They do not represent a complete risk assessment and they never represent a complete undestanding of the trade they may apply to.

Standards very commonly lag technology and trade practice by 5, 10 or more years, and they often have nothing to say about significant issues that have prevailed for decades.

AND as many of us who work outside of the main line trades find on a daily basis. Much of the standards work is completely ignorant of issues that occur outside of the main line, because only the main line and the large players are consulted.

The welding standards are one of those that for most in the trade represent a fart in a sewer in comparison to daily welding practice.

cheers

Hi Bantam
Olcoolone thinks I need urgent help – psychiatric I assume.
Maybe you should book in for a check-up too.

The Bantam says:

........."One thing we know about any type of standard is that they NEVER represent a complete understanding of the matter"...........

It would seem that our industries are wasting an absolute fortune on promulgating Standards as they are a total waste of time and resources and no-one other than The Bantam has yet to perceive that.

Clearly, all that is needed is to refer to The Bantam for guidance, for in him resides the entire world's wisdom and knowledge in anything technical (and most other stuff also).

Disclaimer of sorts: ...... I think "LOL" covers it.

Some of the standards are both necessary and helpfull.

But there are a lot of them that are a complete waste of paper, time and money because all but the institutionaly office bound never read them.

There are hundereds and thousands of dollars wasted on producing standards very few read every year.

The majority of work is not conducted to their spec, and they are not compulsory.

Even worse, because of the pricing structure, almost without exception standards are inaccessable the the majority of the working population.

I have just costed the price of buying 5 standards that I realy should have, and it is going to cost me over $1000 to buy them.

Because I am conciencious I will...with protest pay the money, where as the vast majority will simply say...piss off I will not pay that for such a piddling volume of paperwork......and they will do without and remain ignorant....like the vast majority of electricians.

If you doubt me ask a few electricians to produce a current copy of AS3000.

If I baught the standards I realy would like to have on hand & would be helpfull to me, I could easily spend $2000 to $3000.

AND then I would have to spend that again when they are reviewed or ammended...which would be no longer than 5 years.

AND I can not access the whole text of a standard at my convienience any other way than buying it.

Mate as far as knowing stuff...yes I do.....if you want to waste your brain power reading murder mysteries, watching home and away and killing brain cells with alcahol...off ya go.

But don't winge to me that you know less than I do...thats not my problem its yours.

cheers

Absolute classic!

Listen up........The Oracle has spoken.

All sweet Dennis...LOL

As Bantan had said, standards are a very funny thing and in some cases doesn't represent the whole picture.

The only time I personally look at standards is to get a reference point to work from or to, most of the information in standards in my industry mean very little in real life situations and in nearly all cases we exceed the minimum requirements of the said standard.

The down side of standards is they don't cover the law side of things so what a standard may say may not apply in law or in some cases the law says different.

Standards set the minimum something has to comply with.

HI
To all those good people who want their job correctly done
DO NOT EMPLOY THE BANTAM
He cannot afford &r does not believe he even needs to have Standards let alone UPDATED ones

Perhaps he is still using the originall SAA 1934 version
It had a lot about extra&low low voltage DC!!
[low voltage bell wiring included]

The Standards AS/NZS 3000 is a MANDATORY STANDARD THROUGHOUT AUSTRALIA!!
IT IS a legal requirement mandated by the various STATE Regulations & ELECTRICAL ACTS.
ALL work started from the date of each revision SHALL COMPLY to THAT LATEST EDITION.

YES, the STANDARDS DO SET MINIMUM requirements
But that means those minimum requirements must be met!

But how does a person who does not have them or keep updated KNOW they are meeting those minimum requirements???


IT is impossible for any Standard to cover every eventuality, but understanding the INTENT of the various sections will usually allow the KNOWLEDGABLE person to FULLY understand the possible implications of doing something that is not specificcaly covered!!

Unfortunately some take the other path of seeking to find ANY possible means of avoiding the requirements & not worry about the possible consequences!!!


PeterQ

HI
A little more on the Standards since a poster believes they have no real life experience to match hisl

Regarding the Standards Committies.

Perhaps some should do some research on who makes up the various Standards commmitties

They actually consist of a wide spread of interested parties
Certainly not UNION dominated,
Not loaded with gov beaucrats
BUt by EXPERIENCED people in the MANY fields

Many/most of the rules are the results of past experiences or forseeable problems
They are both REACTIVE & PROACTIVE

Almost all are developed around SAFE use of electricity!!

But to really UNDERSTAND THAT, one does need to be able to see & undersstand the REASONING behind EACH particular rule.
THEN they will see how they ALL interlock /react

Only then do some of them make sense & one can see & understand why a single breech can cause problems

One other point the Electrical standards are far wider than just ONE Standard, AS/nzs 3000 [Wiring Rules]
I have never fully counted but there are something like 40PLUs main Standards involved covering ALL aspects
Tthen there are many cross referenced Standards for the safe design of ancillary equipment /appliances /accessories
The average domestic electrician probably can make do with jusy one As/NZS 3000
but an electrician wiring both houses & "Transportable "structures" needs TWO AS/NZS 3000 AND
AS/ NZ 3001
Then if he also does BOAT wiring he needs AS/NZS 3004
Solar? ADD another one!
& the list goes on!!
Symon can add other relaitive to mining & other fields
THe deeper one is involved in various levels , the more Standards one needs to have AND UNDERSTAND!!
AND THE MAIN CRITERIA OF ALL?, IS SAFETY

Perhaps our anti regulation posters are not aware of ANY of THAT either!!!

PeterQ

Peter Q,
just for your interest and others. This is a copy of the safe running of winders in mining. When things go wrong with them, it goes wrong in a big way. The winder at Roxby downs is one. The conveyance got within in 60 metres of the surface, and then went backwards. 50 tonne going backwards some 350 metres causes a few problems. Everything totally wrecked. As fortune would have it no one was in the area. Word was a software fault caused it.

Mine hoisting systems

These winders have a strict maintenance program and are subject to some very heavy standards and mines regs. To understand those requirements fully, you have to either operate the winder or be involved with maintenance of it. They are recommissioned every year, shaft inspections are carried out every week, also the winder is driven outside it's design parameters to test that the fail safe systems operate correctly. Monthly maintenance is also carried out to a strict program. The mines inspector will go up and inspect all documentation at any time, to see all standards are being enforced. Here is a photo of the weekly test page where all tests must pass. (Note!) the use of 110v DC and 24v DC for control. Also the brake cards operate on 24v dc being backed up in emergencies by small gell cell batteries.

Normally you can never lock out on an e/stop, but this winder can be locked out on any of it's 8 e/stops that are on many levels. This was signed off by the mines inspectorate. That is how good the supervision, adherence to standards and maintenance are.

Even the 50-1000v ac low voltage has been accepted as 50-1100v in mining by the inspectorate. All u/g mines run 1100volts u/g.

OMG!

I feel so sorry for the OP and his question which has obviously been long forgotten.

Gives him something to read, while he is throwing that charger overboard for use as an anchor.

Just giving Batam a little tickle up, he should be ready to bolt his spurs on by now.

old track mate, you have just shown how little you know about electrical standards in the real world

IF like the majority of electricians you believe all you need is AS3000 you are very much mistaken.

EVERY full ticket electricain should have daily and immediate access to AS A MINIMUM

AS3000 SAA Wiring rules.
AS3008 Electrical installations, selection of cables
AS3100 Approval and test specification- general requirements for electrical equipment.
AS3760 In service safety inspection and testing of electrical equipment.

Every full ticket electricain should carry copies of the above in their van or if confined to a building or site, available for immediate reference.

You can not work to rule as an electrician without a comprehensive knowelege and daily access to these 4 standards....minimum

If you are involved in other activities, are further qualified than the certificate 3 basic trade or you are an employer or contractor the list of standards you realy should have just becomes mind blowing.

Back 20 years ago when I was working for and with a few electricains and had mates that where young electricians, every one of them I worked with or knew, had a dog eared copy of AS3000 close to hand, good employers gave a copy to an apprentice with his first pair of pliers...back then the tables in 3008 where in 3000.
But that was before australian standards where commercialised and the price of standards skyrocketed to the current rediculous state.

Front many electricians these days and they will not even be able to produce a current copy of AS 3000....some are still scratching their heads and wondering where the tables now in 3008 went.
I know several electricains who rely on their yellow covered 1991 copy of 3000 for the tables that are not in the newer versions and you have to pay more for....if ya know 3008 exists.

Then there is the issue of the cryptic nature of AS3000 after the 1991 edition.....back when the book was yellow it was reasonably easy to read and understand how the work should be done, now most electricains need either " engineering advice" or a crystal ball.
No wonder so many older electricains still cling to their old yellow 1991 edition of AS3000

I am not a full ticket licencee, but I do own ( have paid for with my own money) recent copies of the above.
But I do not have the very latest....add a couple more specific standards of intererst to me and it will cost me over $1000 to replace those standards....go price them if you like.

That is over $1000 for six paperback books, some of them with less than 20 pages and 6 of those pages may have useful information on them.

I do have and do carry current copies of communications standards and telstra "authorisation to alter".
Which BY the way are free to down load, as all standards should be.

As for working on boats, unless you are working on commercial shipping or small boats subject to survey....there is no applicable or compulsory standard for Extra low voltage wiring in boats in Australia....AS3000 series prevails for "electrician's work".


As for those who sit on the comittees for standards......some of those comittees are very small.

Unlike most high priced Australian Standards, the communications standards actually list the names of those on the committe and who they work for, in the back.

The communications industry walked away from Australian standards years ago, because the process was simply too slow and expensive AND Australian Standards made such a mess of the first attempt at the communications standards.

So, ya got a list of names for the AS3000 comittee and what vested interests they represent....bet ya there is no one form outside the main line electrical industry

As for useless standards.

years ago when I got into TV antenna installation, I actually baught the standards.....well, what I could not get out of the Hills catalogue was pretty well comprehensivly ignored in the industry and remains so today.

Those doing work for any of the pay TV carriers, don't give a rats about the AS standard for TV systems......they care about S009 the communications standard ( did I mention that it is free) and the documents they get from the carrier they contract for.

People wonder why we have such massive compliance problems out in the real world.
Perhaps if the standards where better written and they where available at a reasonable cost, people coul be bothered with them things would be better.

cheers

Forgot to add, one of those anti static straps fro the cars on the trailer
will stop it if it's touching the ground.

Sorry but this has not a thing to do with capacatance.

And the belt you can get from a TV socket can be a lot more than a tingle.

having been involved in TV antenna installation the 50 odd volts that sits on an unterminated TV inlet can give a fair belt, particularly if you are sweaty in the customer's ceiling or 20 foot up a ladder.

and those antistatic straps do bugger all.

cheers

Having been a television repair for 35 years I can tell you the kick of a tv is caused by capactive coupling and can be a lot higher than 50V!

The tuner runs on around 12V DC, the AC bite is caused by the bypass capacitors.

The aerial connection of the tuner has to be isolated via capacitors from the live chassis (not SMPS) else you would be dead if you touched it!

Even with SMPS, in an unearthed set, the 240V live side is usually coupled to the the isolated side by suitable isolation capacitors. The floating voltage on the tuner socket is caused by the superimposed ripple on the power.

Leigh

To shorten the discussion, from a text:

The PSU (power supply unit) converts the raw 220V ~ 230V mains into low voltages for the equipment's circuitry
and isolates the mains from the low voltage side ... well ..... almost.

You see, all power transformers, whether they are designed for a switch-mode supply or linear supply, they all
leak a "small" amount of current from the primary to the secondary board earths due to stray capacitance.

In double-insulated items there is no "REAL" earth as in earth to "GROUND" per se available to use as a shield
between the input and the output, so the power supply is designed as far as possible to minimise the leakage
due to this unavoidable "leakage" effect.

Unfortunately, switch-mode supplies run at very high frequencies, so the smaller capacitance in the smaller
transformer ends up leaking just as much as the larger capacitance in a larger transformer running at 50 or
at 60Hz for example.

To the top of this page

LEAKAGE ? uh ?......

The leakage current is usually less than 1mA and is often as low as 10uA, but even at such low current, it
can still present and still can cause problems.

I have no argument that the voltage at the terminals of a TV input socket is due to capacitive coupling...my argument there is that what comes out of a TV is a lot more than a tingle and due to the high votages floating around inside....voltage in the KV.........but that has nothing to do with the battery charger.



I think is is a very long stretch that there will be sufficient leakage or voltage at the terminals of a battery charger to give a shock due to capacitve leakage.

The primary switch mode or transformer will be tied to the greater mass of earth via the neutral pin and that will surpress leakage to a certain extent.

secondly there will be DC present an all manner of electronics to load down leakage in some way

Thirdly the voltages within the charger are orders of magnitude less than those found inside a CRT TV.

If as you say the leakage is in the order of 1 to 10 mA, it takes very little to load that down and its hardly enough current to be even felt.

I have worked with all sorts of DC power supplies and battery chargers large and small, I have poked and prodded them, chased earth loops that are caused by the leakage discribed but have never, experienced a shock or even so much as a tingle between the output and earth.

But I have touched the body or frame of a vehicle and and a live 12 volt terminal and felt a most definite tingle.

Serouly folks.

get ya self good and sweaty lean on the engine block or some clean earthed metal and touch a positive battery terminal.
Carefull now don't bump ya head on the bonnet.

anybody ever touched a good 9 volt battery to their tongue.....thats a bit more than a tingle now isnt it.

Now futher evidence.
this bloke has an aluminium battery box.
the most likely thing is he is getting a tingle between the chasis (connected to the battery box) and the 12 volt terminal of the charger or the battery.

cheers

If you have read the original post If you actual read the OP you would have noted he wrote the box and the chassis are connected to the battery negative terminal, so it would be a bit hard to get a potential difference between them with a small charger.

It sounds more likely that the earthed person touching the unearthed trailer feels tingle.

Yes the trailer and the battery box are bonded to the negative terminal of the battery.

If like most people the user connects the negative terminal first.....feels nothing then holding a poorly insulated positive terminal leans on the metal battery box.......yep a decent tingle guaranteed.

cheers

Bantam, did you actually read what Tim said at 13:53..............

"The shocks are felt when touch only the aluminium box not terminals or anything like that. I would suggest that indicates a potential difference between the box and earth."

I think we are arguing over a pile of chineese wispers here.

I doubt that any of us know exactly what procedure is involved here.

is said person wearing shoes, what else is he in contact with.

What else is connected to the trailer.

Until someone goes down there are actually sees and tests what is going on its all conjecture.

The idea of an aluminium battery box don't sound to clever to me either.

cheers

The Bantam posted:
Yes the trailer and the battery box are bonded to the negative terminal of the battery.

If like most people the user connects the negative terminal first.....feels nothing then holding a poorly insulated positive terminal leans on the metal battery box.......yep a decent tingle guaranteed.

cheers
[end quote]

Ditto
The voltage peaks are normally well in excess of 12V

& that is what is fealt ,THE PEAKS


PeterQ

The power supply must have an isolation transformer else it would described a live chassis.

In a live chassis circuit the chassis floats at 325V DC, it would give you more than a tingle!

The charger willl not doubt be a SMPS unit.

Leigh

Hi Tim,

The charger will definitely have a transformer which isolates the primary and secondary circuits. But it is probably not a large iron-cored transformer but a "switchmode" type where the incoming 230v mains are firstly rectified to DC then converted to high-frequency AC, passed through a small ferrite-cored transformer to become about 20v AC then rectified and regulated to become the DC output. Isolation is maintained.

Yes, to feel a "tingle" there must be a potential difference between the box and earth.

You may feel a "tingle" without tripping the Earth Leakage Protection as they trip at 30mA and the tingle may be less than that. OR, the EL protection may be faulty and failing to trip at higher leakage.

As I have said elsewhere, if you can feel a tingle, have it checked by a qualified electrician.

A lot of the OHS documents state that AC is more dangerous than DC because AC is more effective in stopping the heart.

Because AC is a more efficient simple killer they declare it more dangerous.

There are also arguments that AC is more frequently implicated in deaths.

There have also been studies that state that the current published polocy on electrical hazards is inadequate because those making the polocy have not considered all the factors involved.

In fact the general published polocy world wide is bassed on a very narrow understanding of the risks and a largely penned by and for an industry doing a fairly narrow range of work...mostly the 50/60 Hz electrical industry.

This is an argument similar to what the most deadly snake is.

It is very clear that one or two of our snakes have the highest ability to kill humans, but there have been very few incidents with these snakes, so some people consider them less dangerous.

a semantic argument.

What can not be argues is that DC presents a different group of specific risks.

AND that DC even at low voltages can and does kill.

AND when DC does kill it is often by a mechanism that is not related to stopping the heart.

the thing to take away from this is that DC even at low voltages is not the harmless thing that many people think it is.

12 volts DC is far and away safer than 240V AC, but it is far from harmless.

Every year we have cars boats and caravans burn down because of DC electrical faults.

There are clear and well understood hazards involving high current DC circuits like we find in engine starters and winches.
Energy sufficient to blow big holes in metal if shorts occur.

We need to exercise due care with DC.

cheers

The other reason why AC may be seen as more dangerous is everybody is in contact daily with high voltage AC and AC is used for more power applications whereby DC is more industry specific.

It might be a simple fact of warning the majority of the main AC power source and not the little know DC source...... KISS theory.

I always got told anything greater than 30v is dangerous.

Maybe the debate of which is more dangerous dates back to the 1880's when Edison was promoting DC and George Westinghouse with help from William Stanley and Mr Tesla were promoting AC.

And nearly 150 years on we are still having the "Westinghouse vs Edison" debate.

The AC Vs DC debate very much goes way back to the very beginnings of electricity.

Eddison's stubborn insistance that DC reticulation was the way to go cost him dearly, like, lots of real money ( I have read a biography). His pro AC competitors played very heavily on the very real and inherant dangers of DC.

There where a couple of unfortunate and spactacular incidents in Eddison installations, which did not play out well.

DC generating plants and switch gear of the period would have been frightening to watch.
DC's tendancy to maintain long and steady arcs, that makes it excelent for welding makes it very hard to manage in machines and switch gear, particularly in high currents and voltages AND spactacularly dangerous when shorts occur.

It was argued very reasonably that DC was far more prone to causing fires than AC......this was a real problem for Eddison because he was heavily pushing the idea that Electricity was far safer than gas or oil for lighting.


so we move on to the current.

Very much the current perception and polocy on electrical safety originates from and is framed for the main stream "electrical industry" and more or less ignores a whole heap of variants used outside that industry.

Until recent times the modern main stream electrical world has had very little to do with DC and only saw it in relativly small and relativly safe applications.

Most electricans would never encounter a 2000 AH 50 Volt battery and would have no awareness of the massive fault currents and explosive consequences of short circuits in associated systems.
A 5000 Amp short at 50 volts would easily blow ya hand off and there are several ways such a system could kill or injure you....possibly the least likely is stopping your heart.

We in the public address industry have fought the electrical lobby for years, who still try to tell us the "100V" speaker lines are electricians work and subject to the same wiring requiremenst as 240V power.

Where the nominal 100V almost never occurs and is never capable of delivering the sorts of currents and resultant dangers of mains supply.
Than goodness for S009 apendix G.

Most electricians would not encounter the high voltages used in televisions, medical equipment, other electronics and certain lighting applications.

If taken verbatum and word for word, the electrical definitions and regulations would make a hell of a lot of things and activities illegal.

Electric fences for agricultrual purposes for example would be illegal.

The acts and regulations had to be specifically altered to account for certain things in modern vehicles like HID lighting.

Thus those of us outside the main stream electrical trades have struggled and faught, the mains electrical centric voltage definitions and the view of electrical hazards.

We have also faught the electrical lobby who continue to annex and control anything they possibly can and make it electricians work.

Back in the 90's there was a move by certain people in the electrical lobby to make DC electrics a licenced and regulated trade.
Fortunately that was firmly slapped down as being unnecessarily restrictive and impractical.

All of the above focuses the view of electrical risk very narrowly and very much centered on stopping the heart, to the point that as we have seen people will not even believe that other risks and modes of death and injury exist.

In many of our vehicles and trailers we have 12 volt systems capable of delivering fault currents in the reigon of 1000 to 2000 amps.
That presents a definite potential for damage, and injury.

As I have said DC electricity is far from harmless and deserves more respect than many people give it.

cheers

Hi Bantam
IMHO,you are confusing the issues.

[a]The Science of electric shock has been well researched

[b]There is NO DOUBT that under the SAME conditions .[including voltage& available power},AC is safer from an electric shock point than DC

[c]You are corect with the ARCING problem of DC
One of it's early drawbacks when high voltages & high currents are involvedwithold mechanical switching , BUT that has NOTHING todo with EL over many yearsECTRIC SHOCK

[d]The move to AC overcame the problems of Loooong transmission lines
Much simpler, less maintainenance , etc to use transformers instead of rotary convereters ,especiall with extra high voltages.


[e]RE [Quote}" Back in the 90's there was a move by certain people in the electrical lobby to make DC electrics a licenced and regulated trade.
Fortunately that was firmly slapped down as being unnecessarily restrictive and impractical."[end quote ]

Sorry, RIPPLE FREE DC above 120v is still regulated & SHALL comply to theAus Standards & has been for many many years
IF the DC has a high ripple content then it is regulated wheh it EXCEEDS 50V
Again this indicates it is the PULSEING & voltage peaks[nature /component ] that encreases the risk


[f]then to further ciompllcate matters, at very high frequencies
voltages even as high as 3000V arcing to the body may only give a slight burning sensation proved it is current limited

[g]YES, WATER & ELECTRICITY IS ALAWAYS A BAD MIX
BUT under the same physical & electrical conditions EXTRA LOW voltage DC IS less likely to be a SHOCK risk than EXTRA LOW VOLTAGE AC,


PeterQ

HI I cannot edit
So Ammend" b]There is NO DOUBT that under the SAME conditions .[including voltage& available power},AC is safer from an electric shock point than DC""

to"=========DC is safer ======than AC"


PeterQ

To Timm
I will repeat my earlierr comment & reinfonrce Brian's
ANY tingle Should be investagatec IT could be some thing potentially more serious developing .

One isuue that has not been raised may lie in answers to these questions
[1]: did this only occur in
ONE LOCATION?
[2]Was A long extension lead in use ?
[3] was the eath wet ?
[4]Was the camper making electrical contact with EARTH
[5]Through what part of the body was contact made between the camper frame & MOTHER EARTH?


IT may all be due to either a faulity extensin lead,poor eathing connection
OR Step voltages cue to ground currents !!

As if this is not confusing enough already................

Who is Brian?

Agree with you on the tingle oldtrack. Any sort of shock in a mine has to be investigated, whether it be from static, low voltage or extra low voltage. The electrical mines inspector has to be notified as well. All our welders had VRD's (voltage reducing devices) due to a welder being electrocuted. They will not supply full volts until they see a low resistance.

We had a case of long hole drillers getting shocks 300m underground, because they are always wet and the ground is very salty, shocks can be felt easily. The sparkies took it seriously and found stray 6 volts between their earth and the surrounding rock. They couldn't trace this source and turned off everything, including the HV. The 6 volts remained and miners still get a tingle in that area. Cause unkown.

Tim,
I know cheap battery chargers that change the sine wave cause big problems with boats ( these are the ones that half rectify the sine wave) . If the battery is not isolated, the anodes cop a hiding. So one concludes there is leakage. This maybe your problem as the voltage is not constant.

SO oldtrack

It may well be that when in the same conditions including available voltage and power DC is safer than AC, IF only considering electric shock assessed from the point of view of stopping the heart.

But that view ignores a range of other risks and context

Unfortunately the way AC and DC are used, they are not found in the same proportions and they are not found in the same conditions.

AND as I have said before the mechanisms for injury damage and death are different.

If by some strange twist of fate we ended up with a 110 or 240 volt DC electrical system, we would probably be less concerned with stopping the heart and more concerned with other issues like fire, electrical burns, asphixiation due to muscular paralysis and secondary injuries.

OH..wait now...are we having reports of solar installations that run fairy decent DC voltages causing fires.


IF DC was to be reticulated, high voltage reticulation would not have been used.....can you imagine even 240 volt switch gear that has to be 10 times the size of what is currently used just to deal with the DC switch arcing



The move to AC allowed a hell of a lot of things...for almost every mechanical need AC is more efficient....for distribution AC is more efficient....for generation AC is more efficient.

Eddison was very much pushing things up hill with DC

BUT the prevailing issue that spelt the death of DC reticulation was fear and a perception that it was less safe.




Yes I do know that DC work over a certain voltage is regulated just like AC work ......But there WAS a move back in the 90s to regulate and licence DC electrics in the Extra Low Voltage classification.....fortunately this failed.


We keep comming back to the reality that the original poster could have been getting a tingle because of a simple 12 volt DC source.

Like just about every fault a technician encounters.....the reality and the solution can only be arrived at by looking directly at the situation.
The customer's account of the situation is very rarely accurate.

As I posted very early on, the situation needs to be properly investigated.

cheers

Bantam,
very simple answer to the dc/ac thing is.

WHO CARES. Go and get some hash and chill out.

HI Allan


Sorry, MY boo boo
At least i did not refer to you as "rooster"smile]
Brian is ANOTHER WISE knowledgable man on another forum!

PeterQ

Hey Peter, have a look at this link. Appropriate?

Many years ago I was sent to investigate a problem whereby a housewife was getting a shock off her metal rubbish bin.
This rubbish bin was sitting on sand at the back of the house and not touching any part of the structure.
The fault ended up being a broken neutral in the incoming consumer mains.

HI
Yes THAT is quite possibly the case in this situation, which is why I asked certain questions pertaining to earthing ,extension leads, etc

Faulty neutral connections nearby are the usual cause!!
Which is a GOOD reason why such incidents SHOULD be INVESTIGATED
if left uncorrected serious shocks may ocuur anywhere in the area!!


Bantam
AS I posted" UNDER ALL like for like conditions, DC is safer than AC"

NOTE THOSE WORDS" LIKE FOR LIKE" from an electric shock point of view


Many other factors need to be considered regarding FIRE risks, etc

BUT
THIS THREAD IS ABOUT ELECTRIC SHOCK!!!

No it has been made into a thread about "electric shock".

Its a thread about a bloke getting a tingle.

Most probably either a simple 12VDC tingle or perhaps some sort of low level leakage.

If you want to expand the risk profile beyond that....."Electric Shock",particularly focused on stopping the heart, is only one of many risk factors.

Modern electrical fear and the regulatory responses to it has become so shock focused, that people, don't understand, fail to consider or as we have seen, flatly refuse to believe other risk factors exist.

They have also become so paranoid about electric shock they have conipshons at the slightest tingle...even when there is not a likely 240V source of danger involved.

we have people paranoid about electric shock on one hand but completely dismissive of the very real dangers of running portable sources of supply such as inverters and generators that have no portection in high risk locations.

Yes people are paranoid about shock, but they will not be told that certain situations are potentially hazardous, and wont be told till some one IS shocked.

its a thaught too late.

cheers

HI
OOooh, MY GOD, how much longer ?
Thecorrect responce from most has been
[1]"do not ignore a tingle
[2]Have it investigated
[3]It could be a warning of emerging problems


A tingle today could be a killer tommorrow.
It cannot be assumed that the possible fault will cause the RCD [if fitted] to trip

Certainly not if it is due toa faulity neutral connection in another part of the system
The fault can even be in the supply authorities system!!

Beyond THAT ,ALL the posts about the mechanisms& the variious causes electric shock are irrelevent
The other point is the margin between a" tingle" & SHOCK can be quite small

MY FINAL message to ALL
IF you EVER experience a tingle due to Electricity HAVE THE CAUSE INVESTIGATED
The cause may be simple & easily rectified or it could be the forerunner of more dangerous SHOCKS.

DC of the same voltage IS KNOWN TO BE SAFER under SIMILAR situations than AC

The current that can cause a tingle is only a few milliamps
But currents in excess of 10mAps can in certain circumstances kill[the reason why nursing home etc use 10mA rcds]
Currents in EXCESS of 40mA are recognised killers
[the reason why Standard domestic type RCDs are rated @ 30mA ]

Allan's link to the Dr's article is well worth while reading
He,the Dr has given permission for it to be used when ever/ where ever it may help people to undertsand


PeterQ

And NEVER go swimming in a pool with your camper trailer. At least not at night when the lights are on.

HI
Poor Mainey
Now there was another" knowledgable" one??
He seems to have completely disappeared from ALL forums

PeterQ

A warm welcome Brian, You clearly understand the subject.
What would you say to Tim, the original poster?

Thanks for the welcome Allan.
As I said in my post, the problem, based on the evidence provided, is most likely mains related.
Any "tingle" that is felt when on mains power should be treated seriously, and measures taken to rectify the problem.
Because the charger is connected via a 2 pin plugtop, then we tend to assume that it is a class 2 (double insulated device), but is it?
It is possible for there to be an isolation fault in the charger (even a double insulated one) that is permitting some crossover to the 12v side, this is more likely in a transformerless charger as this small one likely is, but it is possible in any device.
The box is grounded to the trailer, so a tingle is likely to be felt at other spots on the trailer as well.
The first step would be to test the isolation integrity of the input and output of the charger as, again based only on the evidence presented, this is about the only place the fault could be.

Exactly.
.

The "old" devices had iron core transformers incorporating an earthed screen between primary and secondary windings. This afforded good isolation between the incoming 230v mains and the Extra Low Voltage secondary circuits.

The newer Switchmode devices bring the 230v right onto the printed circuit board before converting it to the ELV output. Isolation is provided by a high-frequency transformer on the circuit board. Even with careful design & construction there is possibility for leakage from mains to the ELV section by tracking across the board due to moisture or dirt.

Such events may be rare but possible and reliance is then placed on RCD "safety switches" which themselves are not always reliable. So Lady Luck becomes our guardian angel.

Those of us who know and are prudent concur........ "If you feel a tingle, get it checked".

In my opinion RCD's give too many a false sense of security, if you are insulated from ground and make a circuit between Active & Neutral then you are a bit of toast unless you can dissipate >30ma to ground and cause the RCD to trip.

cheers