Safety First

christosemv said:

Which are the limits of Voltage and Ampere that an electric vehicle battery pack becomes dangerous for the human body ?

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Simple overview here - It's the current that kills

I've worked with 500A charge sources at 12V, yes I'm careful but feel safe.

Anything over 36V makes me nervous.

so for example with a simple 36 Volt battery pack and a typical human resistance between 0,5 kw - 1kw ,it can be dangerous right ?
I= 36/0,5 = 72mA
Does the capacity (Ah) of the pack plays a part to an electric shock ?

Sure, if a short is passing through YOU.

Even at 12V a large bank of high discharge chemistry will melt a crowbar.

So the capacity (Ah) of the pack plays a part to an electric shock ! right ?

christosemv said:

So the capacity (Ah) of the pack plays a part to an electric shock ! right ?

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Not really, no. You can start a fire with a 1.5v AA battery. It's all about instantaneous amps delivered (and killing a person only requires about 100 milliamps under the right conditions).

See also http://www.darwinawards.com/darwin/darwin1999-50.html where a sailor apparently electrocuted himself with a 9V battery in a voltmeter (although there is still some skepticism about this particular case).

Dry skin is a very good insulator at typical voltages so usually you don't get many amps delivered to your heart - V = IR after all. But there are many ways to violate that "dry skin" condition. So, wear insulating gloves, use insulated tools, and try to avoid current paths through your heart (the old "keep one hand behind your back" rule).

Voltage does play a part, too - something that is an insulator at low voltage may not be an insulator at high voltage - but it's the delivered amps that kill.

I believe 72V and up is what must be identified as hazardous by orange sheathing/insulation in automobiles. That's getting to the voltage where enough current can be pushed through your body to cause problems.

But as previously mentioned, you can do a lot of damage with lower voltages as well, especially if you have a lot of current capacity, as with any EV battery.

madderscience said:

I believe 72V and up is what must be identified as hazardous by orange sheathing/insulation in automobiles. That's getting to the voltage where enough current can be pushed through your body to cause problems.

But as previously mentioned, you can do a lot of damage with lower voltages as well, especially if you have a lot of current capacity, as with any EV battery.

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Good to know. I have been wondering about this as well. I am building modules for a battery pack. Each module is around 40 volts. There are 10 of them. Total system voltage is around 386 and amperage is around 325. I am assuming that I am going to have to be really careful of that last series connection.

Nothing should happen, but you can put a load in to limit current if you are worried, then take it out if there is no spark.

I would be more worried about accidental short-circuits.

christosemv said:

Hello everybody ! I would like to ask about safety to battery packs ! Which are the limits of Voltage and Ampere that an electric vehicle battery pack becomes dangerous for the human body ?

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I guess you are thinking of "electrocution" dangers ?
But it depends what you think of as dangerous.
A simple single 3.7v 18650 if shorted can burn your fingers, or face and eyes if you are close. Or if undetected it can start a fire that burns your house down whilst you and your family sleep !!
That is just as fatal as 1000v across your heart.