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Is it safe to do electrical work on car in rain or snow?

Maintenance/Repairs
#21

I also have never heard of anyone being harmed on 12 volts. But, the safety department in the electronic company I worked for, claimed there were very rare cases of people who were harmed at such voltages, usually with rings on their fingers, and then you have to get it somehow across your heart AND be a rare person who is especially sensitive.

Though the wedding ring as someone mentioned can burn your finger badly if it gets across the 12 volt connections. I stopped wearing wedding rings in the late 60ā€™s and still do not. I donā€™t need a wedding ring to keep me straight.

I say again, I never personally knew anyone who was harmed below 28 volts.

#22

I have a Van de Graaff generator the puts out 100,000 volts.

This thing actually creates lightning!

You can put your hand on it and itā€™ll make your hair stand on end. Thatā€™s because it produces no amperage.

Itā€™s not the voltage that kills.

Itā€™s the amperage.

Tester

#23

Calling electric current ā€œamperageā€ is like calling distance ā€œmileageā€.

#24

I had to go out and tuck my wifeā€™s hens in for the night. She went off to some church thingie and itā€™s a cool night. While I was out there, I remembered the theory why it might be possible to get shocked on 12 volts. At the time they told us that, which was many years ago, we talked a lot about it trying to imagine just how it could happen.

We finally realized that a really strange combination of events would have to be involved. Like one case on the planet. :smiley:

My theory was it would be like the Kettering ignition system, sort of. If you have current, and break it, it is possible to get a larger pulse than the voltage involved, like a Kettering ignition system.

And, yes, it would absolutely have to be your time to go, because such conditions would have to be extremely rare as well as the individual to be that sensitive.

#25

I donā€™t know about you?

But I use the terms of electrical science.

Tester

#26

The ampere is a unit used to measure current.
The mile is a unit used to measure distance. Other distance units are feet, meters, light years, etc.
The volt is a unit used to measure electric potential. Itā€™s the potential needed for one coulomb of charge to deliver one joule of energy.

The Coulomb is a unit to measure electric charge, an ampere is one coulomb per second.
The watt is a unit of power. Itā€™s one joule of energy per second.
The Joule is a unit of energy, itā€™s one newton of force over the distance of one meter.
The newton is a unit of force, itā€™s the amount of force needed to accelerate one kilogram of mass at a rate of one meter per second per second.

I didnā€™t need to look any of this up, Iā€™m pretty familiar with the units of science.

#27

Your car battery is capable of 100s of amps but cannot kill you by touching it. Again, it takes the right combination of BOTH to be lethal.

1 Like
#28

Among other electrical safety tests, manufacturers of electric devices must test their productā€™s leakage currents and make sure they conform to UL regulations. Leakage current is an undesirable electric current that conducts between a person touching the device with one hand and say a water pipe or other low resistance ground with the other hand. The testing assumes only the outer surface of the device is touched. For something like a hair dryer, the allowable device leakage current is around 0.2 mA IIRC, but for medical devices like an ECG machine where special electrodes are used to hook the patient up to the machine with a very low resistance connection, the allowable leakage can be as low as 10 micro-amps. Most houses use a back-up system called a ground fault interrupter circuit breaker in case something like a hair dryerā€™s insulation fails, or it falls into the sink where the electric current would conduct from inside the enclosure. Those ground fault circuit breaker receptacles commonly found in bathrooms and kitchens trip at 6 mA I think. You can get a pretty healthy shock at 6 mA, but not usually enough to do serious damage. With current above 6 mA and 60 hz power it can be difficult let go of the device thatā€™s shocking you, so thatā€™s one reason the ground fault breaker limit is set at 6 mA.

So yes it is the current that does the damage. Of course thereā€™s a relationship between current and voltage for a fixed resistance. So 12 volts across a personā€™s two arms might only rarely create enough of a current shock to do damage, while 110 volts in the same situation may well do serious damage, or worse. If thereā€™s a direct conductive path across 12 volts then that conductor could get really hot, and if you touched it (or wore it , for example a ring) you wouldnā€™t necessary get shocked, but a very serious burn might result.

#29

I almost lost a finger to a ring when I was in H.S.
In the military they hammered the dangers of jewelry and machinery into us. The only jewelry we wore on the aircraft was that under our clothing, like our dog tags & chain. Jewelry on an aircraft also creates the danger of shorting a circuit. We very, very often had to work on live circuits, and some of the switch boxes, like the Automatic Flight Control Switchbox on B52s, had open backed switches. When an aircraft is at the end of the flightline orā€¦ worse yet the runwayā€¦ with a belly full of bombs and (on the D-models) wing racks full of more bombs, and a warning light goes off, you donā€™t shut the aircraft down to fix it except in a very exceptional situation. We had over 150 BUFFs on Guam during the bombing of Hanoi and in Dec 1972 took them off continuously, leaving only enough time between takeoffs for the turbulence to clear. Iā€™ve fixed some lined up on the taxiway with a line in front and a line in the rear all waiting their turn to take off.

The military is also where I saw the stats on injuries due to reactions to even a small, minor shock, like hitting oneā€™s head when jerking back from a minor otherwise-uneventful zap. It was almost 48 years ago, however, so I donā€™t remember the details, only the point being made.

#30

It can only make 100,000 volts if the circuit is open, really open, as in the relative humidity has to be really low.
If you are across its terminals, the charge bleeds off so fast that an equilibrium is established at a very low potential. In other words, it canā€™t produce 100,000 volts while you are touching it, unless you are standing on a good insulator, then you are like a bird on a wire, the generator is not shocking you, but everything else in the room will shock you if you touch it.

When you disconnect a car batteryā€™s ground terminal, the electrical system is effectively dead. the whole car is like a bird on a wire. It has nothing to do with positive or negative either. Many older cars had a positive ground, my '54 Ford F100 for example. The British also liked positive ground electrical systems.