Broken cables on LiPo cell - how can I resolder without being electrocuted?

Hello,

I have a 3.7V/850 mAh LiPo cell and the cable got broken. I want to resolder it but I am afraid to be electrocuted even if I am not sure about the energy left in the cell (it was last used months ago).

What should I do to avoid electrocution?

Thank you in advance.

Hi, What makes you think you will get electrocuted? Where did the wire break?

Tom... :)

You will not be electrocuted from the LiPo.

I don’t know how the cable broke, but it broke at the solder point.

Isn’t there a risk of a current flowing from the LiPo to ground over the soldering iron (and me)?

1) Current needs to flow back to the source (so the other wire of the Lipo). 2) Your solder iron is insulated so no current will flow from there through your body. 3) And the power in the LiPo (even fully charged) is not sufficient to electrocute.

Take an Arduino and power it from USB; hook two wires to GND and 5V respectively. Touch both wires (e.g. with left and right hand); do you feel anything?

Take an new AA battery and hold it with thumb and pointer finger on the contacts; do you feel anything?

sterretje: 1) Current needs to flow back to the source (so the other wire of the Lipo). 2) Your solder iron is insulated so no current will flow from there through your body. 3) And the power in the LiPo (even fully charged) is not sufficient to electrocute.

Take an Arduino and power it from USB; hook two wires to GND and 5V respectively. Touch both wires (e.g. with left and right hand); do you feel anything?

Take an new AA battery and hold it with thumb and pointer finger on the contacts; do you feel anything?

Ok for points 2 and 3, but I don't agree with point 1: current flows where it can and if there's a point with a lower potential it can flow to, it will, the ground for instance.

amundsen: but I don't agree with point 1

Your choice ;)

Take a battery and connect one terminal to a lightbulb or LED and the other side of the lightbulb / led to the neutral or earth of you home power. Does the lightbulb or led light up? No because the current can't flow back to the source.

"I don't agree with point 1: current flows where it can and if there's a point with a lower potential it can flow to, it will, the ground for instance."

You are wrong, but better safe than sorry. As Sterretje states and gives multiple proof examples, you need to have a loop back to the source. That's why you have to connect the grounds when you have external component boards send signals to, or receiving signals from, the arduino. Or, different power supplies for arduino and an external circuit.

You need to do more studying on basic electronics. But, kudo's for taking the safe approach when not sure of the path to follow. Now, when the correct path is shown, stop arguing. If you still have doubt, try some of the LED/light-bulb examples given....

amundsen: What should I do to avoid electrocution?

You won't get electrocuted from a 3.7 V battery. On the other hand, starting a fire or having the thing explode if you short out the battery, overheat it, or puncture it are not out of the realm of possibility.

Take care that the terminal you are not working with is not connected to anything; perhaps cover it with tape if there is the possibility of accidental contact. Don't solder to the body of the battery, only to tabs that were previously soldered.

The most important thing is to wear eye-protection if handling a high current device - you don't want a high-energy spark in your face. You're probably OK at arms length, but soldering is not at arms length...