You can touch with your fingers both terminals on a car battery - no shock
When is a car battery dangerous?
As there is the potential for 400 - 500 amps how come it does not shock when you touch both. My own explanation ios that the volts (12 - 14) is not high enough. But how does this square with the arguement that it is not volts that kill it is current.
And if it is not volts that kill why are USA on 110V for safety? and if we want out door powertools for professional use here in UK they are usually 110V for safety reasons.
It may be that it is the crrent that kills but high voltage is required for the current to flow through a resistive medium (eg human body)...correct?
|
Its all down to Ohm's law. Current is proportional to the voltage divided by resistance (I=V/R) - I is the symbol for current.
The current is therefore given by the ratio of voltage to resistance - high resistance or low voltage means that little current flows. Drop a spanner across a battery (low resistance) then you will get your 400-500 amps. The human body, even though it has a lot of water in it, is a relatively high resistance. Even so, people do get shocks from 110V and some die. Anything over 50V is considered to be a hazard.
|
Thanks, makes sense,
But can a 12v car battery ever be dangerous to us? Say the spanner that shorts the circuit what if I was holding that spanner?
|
You would likely get burnt as the several hundred amps would first heat, then possibly melt and partially vapourise the spanner. The battery contents may also boil and if you were really unlucky , shower you with hot acid. I have no practical experience of this , just a thought experiment based on physics and hearsay. ;>)
--
I wasna fu but just had plenty.
|
|
|
... Say the spanner that shorts the circuit what if I was holding that spanner?
You'd probably end up with "King Dick" branded into your palm.........
|
|
Under charge oxygen and hydrogen gas is emitted from the electrolyte: a spark at this time and the gas may ignite within or without the battery. Energy can be sufficient to blow the casing apart, and cause injury from shards and acid. If terminals are shorted, the amps may be sufficient to destroy the link, and certainly got it very hot. I've witnessed an accident in a workshop caused by a bodged connection during charging: quite a bang!
|
|
|
|
It's volts that jolts and mills that kills. 40 volts or so can make you jump, but so can 10,000 volts as long as it can not sink too much current If you bodies resistance allows 10 milliamps DC to pass from one hand to another then you are close to getting killed or at least some permanant brain injury. 110 volts AC allows a high persentage of victims to survice a 2 second continuos exposure 2 second at 240 AV is bye bye for the majority of vistims but the body handle shoke very differently . A shock from a car HT lead can kill you but 9 out of 10 deaths are due to the hole in the back of your head where you hit the bonnet catch. God that hurts. On a more serious note 12 volts is not a problem jamming a spanner across the battery is a no no and connecting or disconnecting a bettery whilst is is being charged is a no no as the fumes as 2 of hydrogen and I of oxygen and if a spark ignites it can blow the top off the battery and spray you with acid. Bear this in mind if you charge a battery that resides in the boot or under the rear seat Merc and BMW use the charging terminals under the bonnet and leave the battery area ventilated. Regards Peter
|
when i had a mondeo the battery exploded with the first turn of the key
One hell of a bang and acid and battery fragments everywhere.
Scared me the mrs and my two little lads, thats about as dangerous as i want to see a auto battery get.
|
|
|
|
|
|
