Chassis Earthing

Instead of "earthing" on a vehicle, call the chassis the "common return" instead.

Fault currents need to be disconnected with suitable overcurrent protection devices, which protect the wiring against failure and fire. Fuses seem to be the most popular devices on vehicles.

years ago there were stripes that were recommended to hang on the chassis of the vehicles... do you know why? to discharge static electricity accumulated on the metal´s! and sometimes when you place your hand in a car and get a shock, then you know it is charged!

Yes, Mr Electronick, is that used now a days? because if there will be no ground connection, such static electric charges do exists, and if we get touched in anyway, it will get discharged through our body, and another case if any wire connection gets loose, and get shorted with any similar point, this short circuited current should flow through any low resistance path before fuse blows.I dont think Chassis grounding will provide such protection.

But still the the method you were saying about the chain or any conductive strips couldnt be seen now days? So what should be done for proper earthing?

Chassis grounding doesn't provide protection - the fuse does that. Chassis grounding saves running loads of return wires back tot he battery and alternator, reducing the potential weight of the vehicle and the investment needed in cable.

they are not for protection, but to send to the ground static electricity! it is formed under certain conditions...

So, Mr PWSLack in short you are going to say that in vehicles there is no way of earthing for "our" protection against shock (connection to ground) other than Chassis grounding, ie for common potential reference/ return path for reduced connection.

There is no need to protect against shock in Safety Extra Low Voltage systems, as might be found in the electrical arrangements within most vehicles, as by its very nature and definition the Extra Low Voltage does not have the capacity to cause shock.

The wiring in most vehicles is arranged to have chassis return to reduce the amount of cable involved in forming electrical circuits, partly to save unneccessary complexity and partly to save weight.

Regardless of the above, there remains a need to provide overcurrent protection for wiring within a vehicle as with every other electrical installation. To do otherwise renders the occupants and others exposed to danger in the event of a fault that has the potential to cause fire through the conductors carrying currents larger than those for which they were designed or intended.

Regardless of the above, many vehicles are fitted with ground-touching earthing straps as a preventative measure, intended to discharge any static electricity that may build up as a result of the vehicle's motion. There are positive safety benefits for aircraft and many occupants of road vehicles claim to have a more comfortable experience in those that are so fitted.

Does that cover everything?

Thank you

People have been killed by as little as 12 volts.

OSHA (the governmental branch in the US concerned with safety of industrial workers) considers anything over 50 volts to be potentially () lethal.

So, even a 48 V forklift system can kill you. But electric vehicles in general, cars for example, can be much higher voltage than 48 V. In the high voltage systems used in electric cars, the chassis is not used as the return for the traction system. Most Curtis controllers (as used in many forklift trucks) do not use the chassis as a return.

FMVSS 305 (for electric vehicles in the US) requires that the traction pack is isolated from the vehicle's chassis.

The logic is that, with a hand resting anywhere on the frame, then contacting any traction-related terminal could cause an electrocution. The more likely event would be a conductive tool bridging a hot terminal and the frame, leading to an incredibly impressive sound and light show before the fuse blows.

Electric forklifts are not considered 'electric vehicles' they don't require registration and do not require licensing (by large and far), you might consider it a vehicle but it's not registered as one so it's not applicable. Most propane forklifts are likewise only classified as a fire hazard, they are not vehicles by the eyes of the law.

Even at 50 volts it would be incredibly difficult to generate the conditions required for human electrocution, the Osha recommendations are more for stupid people doing things in stupid conditions, like soaked in dirty oil, wet, or with large amounts of electrolyte residue around, things like that, maybe someone hold a large wrench around electrical contacts.

But outside of those specific out of the ordinary conditions even good skin contact with a 48 volts battery when the person is grounded would more than likley not be fatal. Even then the potential for human fatality isn't that great because 'possible fatality' means basically that it generates enough current through the human body to in theory stop the human heart, or under exotic conditions cause severe burns.

But death can occur with just a 9V battery - if you are dumb enough!

With due respect to the US Navy, I don't believe that story either. I am at present separated from my copy of the relevant British Standard, but the figures assume an unrealistically low value for the body's internal resistance. A better order of magnitude is the 300-1000 ohms quoted in

http://van.physics.illinois.edu/qa/listing.php?id=6793

Sonny. It does not matter whatsoever. In #13 I measured 150 Ohms, Illinois measured 300 and above. At such imprecise experiment, it is close enough for government work. So are the different standards of 30, 20, 10mA to cause fibrillation in the heart.

U= 0,01 x 150 = 1,5V absolutely worst case.

Yours: = 0,03 x 300 = 9V a definitely old fashioned optimistic worst case. I, for one would hate to rely on functioning defibrillator to trust that one. Thanks, no!

But the fellow #9 was making noises, that some 50V(?) does not make a problem for him. Well, he is dead by me or by you in a russian roulette, anyhow.

I, for one, fail to see any difference in the outcome.

There are two possibilities here. Either you have read the literature or you have done the measurements yourself. I doubt you have ever actually measured the internal resistance of the human body in your life, granddad. As I said, when I get back to the British Standard document I can bring you some science rather than fantasy figures.

Provided return path through the body is available! Person sitting in side the Fork lift does not get the same extra low voltage return path, What soever the person dumb is!

Electric forklifts are not considered 'electric vehicles' they don't require registration...

I gather you did not read the OP question, which is about " Forklifts or any Vehicles running through Battery..."

the Osha recommendations are more for stupid people doing things in stupid conditions,

Many quite competent industrial workers of average or above intelligence are killed by electrical hazards (mainly electrocution and arc blast) every year. An otherwise competent worker will take shortcuts when a machine is down, the plant is loosing $5,000 per hour, and the supervisor is breathing down his neck.

But outside of those specific out of the ordinary conditions even good skin contact with a 48 volts battery when the person is grounded would more than likley not be fatal.

Of course. But arc blast is a real hazard when working around fork lifts and golf cars. And other electric vehicles often have battery voltages in the hundreds of volts, so electrocution is also a legitimate concern.

Is this enough "earth"?

Or maybe this is?

The issue I see here is that you are assuming that a system that runs off of batteries is also part of an earth ground referenced electrical circuit as with how building electrical systems are designed where they get power from a central power transformer that's also electrically part of a larger higher voltage circuit system which all share common physical connections with each other and the earth itself.

A forklift or any other electric vehicle that caries its own internal power supply is not part of an earth referenced electrical circuit so no mater how high the battery voltage is and how much current the battery on the unit is providing during a short circuit zero volts and zero amps are being imparted to the ground that are looking for a way to complete a circuit between the ground and the machine.

Getting a static shock is not actually completing a solid electrical circuit in a normal sense. Its just static charge equalizing itself with whatever the nearest mass is that has a different static charge potential and you just happen to be the best available conductor between them.

Well SCEADVIAN #9, you are as wrong as you can be. And in matter of safety, it can bite your behind, firmly.

Depending on, whose standards you are reading, and how old those standards are, the current leading to heart fibrillations are 30, 20, 10mA. So to be on the safe side, let's take 10mA crossing your general heart area as a somewhat, but not absolutely safe limit, for our discussion here.

Long time ago, I had a proiect along these lines. The takehome info was, That the real resistance to current flow was skin, dry skin. In the neighborhood of 100kOhm. Sweaty or wet, under 10kOhm. Now in all these measurements the measurements were made with a stiff wire sharply cut. The trouble starts, when the skin is abraded or pierced by anything. With 2 such damage to your both hands, or only one, but you standing or sitting in a puddle (think rainstorm or mining) I have never measured over 150 Ohms.

At what voltage do I get 10mA thru 150 Ohms?

U= I x R = 0,01 x 150 = 1,5 Volts !!??!! NO, it is not a misprint. It is an absolutely worst case.

And no, do not take my word for it. Feel free to repeat the experiments. You will get the same results. You may have to have extreme self control to prick yourself repeatedly, or very good painkillers. I won't tell you how I did it, only that I was young and brash.....

Now, I left out intentionally a big factor, to get to this bottom line. The big factor is workplace regulations. Rubber boots, gloves, hard hats, etc, all tilt the odds in your favor. But, people bypass or ignore them at times, especially under pressure. Every time you do that, it is russian roulette.

I am eternally grateful, that I did not witness any such mishap. But, an installer of mine dropped an improperly insulated big screwdriver into a cabinet fed by 48V big submarine batteries. He did not die. He was out of his mind for days, and his eyesight did not return for days. His retina recovered later, almost completely. The screwdriver shorted the busbars and evaporated. we recovered the handle. Neither the batteries nor the fuses noticed.

You bet, that I was a stickler, and made anybody a stickler concerning water in my "low voltage" environment, and safety rules!

Dropping the screw driver on the battery bank isn't a valid point. That had nothing to do with electrocution it's the screwdriver or contacts vaporizing from the short circuit that caused an explosion which caused the mans issues.

If you follow basic common sense precautions with high voltages or large possible currents sources (regardless of voltage) the chances of directly shorting across the heart are extremely low. I'm not saying it's safe, or that you shouldn't worry around high current sources but that as long as you take basic precautions the chances of something bad happening require extreme mitigating circumstances to cause a lethal current.

Even then those limits for stopping the heart don't consider the chances of the heart spontaneously restarting or the fact that CPR in those border line cases will almost always work.

So the general point I'm trying to make would be that the only people that get killed at those voltage levels, are either doing something stupid, doing something in exigent conditions without thinking, or there is a fault in the system itself making something normally safe unsafe.

How exactly does this DC stuff create the heart fibrilation that causes death then?

The ground on a car or fork lift is the body of the vehicle and is usually the negative side. As has been pointed out its to save cost on wiring. It doesn't work that well on the fibre glass cars!

The dangly thing to ground discharges static. Not always fitted - not always an issue.

Somewhere I have a copy of an extract from an American electricians hand book where it points out that you can touch up to 230V to test whether live. Obviously the boys were tougher in those days or didn't sweat as much.

So are you guys suggesting that if I took two thumbtacks added wire to them and attached them to a common 9 volt battery or two in series I could possibly stop a persons heart with that just by tacking them under each arm into the ribs creating a circuit right through their heart?

It boggles the mind with the possibilities!

BTW would that show up as electrocution in the coroners exam or more like simple heart failure?

Yep, with some - considerable - stretch, yep. The wiseguy challenging you is simply that, nothing more, as far as knowledge involved.

Oh, never mind the heart's stoppage.

Leveles, TCM, PWSlack, PHPH01, and others...

I am not a cardiologist, physician, or biophysicist/engineer. However, with over 900 ACLS and PHTLS runs to date; and 58 CPR/Cardioversion saves; and having been a cardiac patient myself and having been defibrillated and cardioverted three times; and having been involved in field trials of six different defibrillators; and having taught Advanced Cardiac Life Support for 18 years... I'll say that I have enough experience in this area to not need to cite some made up crap I read on the internet or heard at the pub or inferred from some papers and equations and ranges of tolerance or errors. Feel free to critique, but please cite personal experience if you want to argue with me on what voltages or currents or electrical paths through the body can cause cardiac malfunction or failure.

I've carried three DRTs( Dead Right There) mechanics to the morgue via the ER. I agreed with the coroner on two - that the mechanic's time was up, and their ticker ticket got punched before we arrived on scene. The jury is still out on whether they died because of an external electrical incident (shock) or internal failure (heart). I'm sure it's possible they died from the jolt of touching the coil or battery. Nevermind. They are DEAD and all they had in the near proximity was a 13.8 volt DC source and some way to get in contact with it. Just about every medic has experience with high-voltage (lightning or utility) injuries. In my experience, the high voltage patients get burned. The low voltage patients get dead.

The third mechanic death, I believe, was caused by the asystole induced by 12 volts DC passing through the heart from the car's battery to the mechanic's hand, and out through his sweaty, saltwater drenched shirt back to the car frame.

Alternating current causes fibrillation by rapidly switching the heart's electrical state. We are not built to pump at 50-60Hz. Any voltage above microvolts easily supercedes the heart's electrical control system. Any amperage above milliamps easily causes myocardial muscle to stop paying attention to both the electrical and chemical processes and do whatever the external voltage/amperage is instructing.

There's a huge difference between the electrical influence required to cause fibrilation or asystole or other arrhythmias, and the electrical energy required to stop fibrilation (DC defibrillation via external paddles or internal electrodes) or to override malicious internal signals from faulty wiring or worn-out muscle (internal pacing or external pacing).

If anyone wants to stop by some day, I am sure we could get some people interested in testing the 9 volt battery and thumbtacks on YOU. I'll stand by with medications and Tincture of Texas Power and Light to bring you back to life. I guarantee you will not live through the experience if we were to swap the thumbtacks for a pair of defib pads, one applied ventrally and one dorsally, or in each armpit.

Please don't try tin foil or thumbtacks or bandaids and neosporin or any other electrode experiments unless you are recording the video straight to YouTube. If you really must feel what your heart would experience with the 9 volt battery, stick it on your tongue. Now, imagine that tight bound up tongue muscle is your left atrium. When there's no repolarization of the sinus node due to the LA being asystolic, you've got around 10-20 seconds of consciousness to ponder how you are going to get that SA node firing again so your left ventrical will contract.

At least, please, if you want to do the experiment, write it out in big letters on posterboard or on the wall behind you so it will be documented in the video.

As I promised, I will bring you the data from British Standard Draft 60479-1:2005 "Effects of current on human beings and livestock". I was, by the way, a consultant in anaesthesia and intensive care, and I have perhaps a little more experience than most on this forum in the electricity of resuscitation.
Figure 22 in that publication is a time-current plot showing zones of effects of DC currents. A current of 150 mA flowing for 1 sec is in zone DC-3, where "Strong involuntary muscular reactions and reversible disturbances of formation and conduction of impulses in the heart may occur..." It is likely that the involuntary muscle contraction will end the experiment much sooner than the full 1 second. If the current flow is limited to 100 msec, the DC-3 zone extends to about 300 mA. Even at 600 mA (zone DC-4.1) the risk of fibrillation is less than 5%.
Next are the questions of the internal resistance and of the current path. Unfortunately there is no definitive figure for the internal resistance, but extrapolating from the figures for body impedance in saltwater-wet conditions in Figure 4, the internal resistance to DC seems to be a bit less than 1kOhm. Furthermore, it is well established (table 12) that the current required for fibrillation between the two hands are higher than a path from hand to foot, the former requiring 2.5 times as much current as the latter. When doing Ohm's law calculations from guesses at the internal resistance it is therefore appropriate to use a higher rather than a lower guess. In short, my informed guess is that the described story is a myth. Even if the USN technician had sharpened the multimeter probes sufficiently to pierce the skin, the resulting muscle jerk would have terminated the current flow very quickly, before any likelihood of cardiac involvement. The story was probably made up by a petty officer to scare the ratings. I may add that I have encountered similarly unlikely stories of other emergency situations made up by civilian paramedics.

Thumb tacks? Not a chance, the current would travel across the surface of the skin mostly possiblt into surface muscles, you'd need to hit major artieries that connect through the heart and are very short for low resistance and very high resistance most other places. The electrodes would be more likley to kill than the battery current itself.