Marine Batteries - Danger or Electrocution?

Molteni said:
You will NOT be electrocuted in the above scenario
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This is correct.

The voltage required for you to even feel it is going to be above 50VDC and this varies person to person. I have read of people touching the terminals of 96V E-Bike batteries and reporting they can just feel a tingle.
 
Molteni said:
The Opening post asks whether a 12volt DC battery powered boat risks electrocution in a capsize. The answer remains a firm NO.
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Great for you that you are so certain! I am not.

As I wrote, this is a "NO" at 99.99% meaning that to be electrocuted in such a case you should be extremely unlucky but I dare suggest that calling it a "firm NO" is not correct.
On the other hand, it is positively wrong to affirm that only AC kills.

Do you have an idea of the order of magnitude of the currents that make a human heart beat normally?

Daniel
 
Molteni said:
Correct, it's only AC (Alternating Current) that kills.
But a 12v DC system could still be unsafe, from acid spillage, short circuit etc
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Having read the above and your other posts on this thread might I suggest you watch this, it's a bit simplified (it is used in teaching at GCSE level) but it might help educate you.

 
Molteni said:
No. Do you have any evidence that a capsized 12volt DC powered boat has ever electrocuted the crew? Maybe a link to a national statistic for cause of deaths?
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Divide that by the number of 12V DC capsizable microboats (about zero?) and you get what?

I think the OP is probably more likely to get killed by capsizing and having the boat circle around and whack him on the head.
But electric shock drowning could be a possibility in fresh water?
 
Molteni said:
To answer the Opening Poster, I think an electric outboard would be a big improvement to the racket of the petrol one in the video clip. ;)
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True, but the petrol outboard was a 3hp version, an electric trolling motor won't give anywhere near the same sort of performance.
 
AngusMcDoon said:
As an aside to anyone interested, and not relevant to the use case here, but 12 Volts can kill if it gets in the wrong place in the body. This is important to medical instruments used during some types of surgery. It's important to prevent currents of more than 10uA away from the heart. The resistance of the inside of your body beyond the skin is sufficiently low that currents greater than 10uA can be conducted even at low voltages. This can be lethal if it traverses the heart. There are strict standards on medical instruments that must be adhered to to limit any currents to less than the safe level, which means low voltages. It's all a bit theoretical as the risks were identified early from animal testing and the standards have been in place for decades, so there are no reported deaths.
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Angus is right. I used to work with an ex MOD chap who had spent serious public money showing that 20 micro amps across the heart is fatal. He never said why they needed to know.
 
Paulg25 said:
This is correct.

The voltage required for you to even feel it is going to be above 50VDC and this varies person to person. I have read of people touching the terminals of 96V E-Bike batteries and reporting they can just feel a tingle.
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I recall in a physics lesson at school that the master arranged two copper plates on a bench with a lead to each supplying DC. He then got a volunteer to place the palm of a hand on each plate whilst calling to a another pupil to slowly increase the voltage. The subject called a halt to it at about 50 volts. Would never be allowed nowadays.
 
Molteni said:
Correct, it's only AC (Alternating Current) that kills.
But a 12v DC system could still be unsafe, from acid spillage, short circuit etc
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That is so so wrong. DC current can be more dangerous with regard to electric shock than AC but not at 12v DC. I can certainly feel 50v AC if my body is part of the circuit (not through shoes to earth) and it is enough to get uncomfortable but not to kill except in exceptional circumstances.
 
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AngusMcDoon said:
As an aside to anyone interested, and not relevant to the use case here, but 12 Volts can kill if it gets in the wrong place in the body. This is important to medical instruments used during some types of surgery. It's important to prevent currents of more than 10uA away from the heart. The resistance of the inside of your body beyond the skin is sufficiently low that currents greater than 10uA can be conducted even at low voltages. This can be lethal if it traverses the heart. There are strict standards on medical instruments that must be adhered to to limit any currents to less than the safe level, which means low voltages. It's all a bit theoretical as the risks were identified early from animal testing and the standards have been in place for decades, so there are no reported deaths.
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The famous - well, in the Veteran and Vintage motorcycle world - Bill Fruin of Benson, Oxfordshire had a pacemaker fitted. He told me he had to be careful around electricity.

A guy bought in a nice BTH Racing Magneto for Bill to look at with a view to him buying it.

Unable to help himself, Bill checked the spark by turning it across the bump of magnetism with the end of the plug lead 10mm from the body. We heard three nice cracks as the spark jumped this gap. Suddenly the Mag fell to the bench as Bill grasped his chest. OH - OH - $H1t - that bloody doctor told me t'er watch out fer that - OH - OH................................

He soon recovered after his wife Wynn made him a cuppa.

I never found out id it was an act - he was a well known joker!
 
As said definitely no concern re electrocution. OP seems to be concerned re electrocution in a capsize. Even if he had a high voltage dc battery ie 200volts as might be used in an electric car there still would be little concern. The current flow would be from battery terminal and wiring to the other battery terminal and wiring. Depending on salt water or fresh water current will be localised to the area between the 2. So assuming you are thrown out of the boat into the water you will be quite remote from the area where current is flowing through the water. Certainly salt water will be a far better conductor than the body fresh water not so much. You might get some conduction through your body if you were in the line of current flow. Still no concern. ol'will
 
reeac said:
Absolutely wrong. AC is more dangerous than DC because it causes the muscles to contract meaning that if you're gripping a live wire you won't be able to release it. With AC the muscles will pulsate and so there's a good chance of releasing. None of this applies at voltages as low as 12v. The voltage at which things become dangerous depends on the conductivity of the circuit ( mainly the dampness of the skin) but will be greater than about 50 volts.
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I think you mean "DC is more dangerous than AC" ...

The rest of it is fine though, certainly below 50V I wouldn't worry .. and 12V even when wet and salty is absolutely not an issue.
 
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