I have a USB type C charging cable that I charge my cellphone with. Couple of days ago I found out that it got frayed on some parts of its plastic cover. I always charge my cellphone in bed and before sleeping. I'm kinda worry right now that I might have rolled onto the frayed part while sleeping and got electrified without noticing it due to the fact that the cellphone chargers output voltage is too low to be felt ( I read this somewhere ) but being electrified for hours ( when sleeping ) even by a low voltage must be really dangerous I suppose. Something I feel heartburn and shortness of breath but I've always had these problems and don't know if they are related to the charger story or not.

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    \$\begingroup\$ You're fine. Get it replaced soon \$\endgroup\$ – DKNguyen Jun 21 '19 at 14:42
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    \$\begingroup\$ Welcome to SE.Electrical Engineering! 5V is not dangerous, even not for longer time. I'm voting to close this question as off-topic because it has nothing to do with Electrical Engineering. \$\endgroup\$ – Huisman Jun 21 '19 at 14:50
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    \$\begingroup\$ Yes, you may be electrified if you happen to touch the bare wires. You will be exposed to roughly 5,000,000 microvolts. \$\endgroup\$ – Elliot Alderson Jun 21 '19 at 14:53
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    \$\begingroup\$ The battery in the cellphone may be dangerous to have in bed with you particularly if it gets under you or the battery is overcharged. \$\endgroup\$ – Charles Cowie Jun 21 '19 at 14:59

Can 5V kill you?

Short answer: YES ...BUT....you'd have to broach the skin to subcutaneous layers or have lots of blood exposed in positions either side of the heart. So with a frayed USB cable (both ground and +5V exposed) an impossibly low risk for such local contact.
If your skin is intact the likely resistance is in the 10-100 kOhms range, so death would be impossible (insufficient current flow).

Reading this or this might help you. It's all about the current flowing.
This diagram is helpful:

enter image description here

What are the chances of a frayed USB cable killing me on contact?

Short answer: Impossibly low risk

I didn't say there is no risk because the situation is complex.
If all that is wrong is the DC cable is frayed and you are not bleeding or have open wounds for it to touch ….the risk is infinitesimally small. Current would flow only locally in the area of contact and you'd be unlikely to even feel it.
However the cellphone charger is connected to the AC mains 120/240V AC and the isolation/grounding on some chargers is questionable. Under these conditions you could get higher exposure ....but you'd need some other contact (typically a ground) on the other side of the body to get current to flow across the heart.

For example, picking up this frayed USB cord (and making contact subcutaneously) with the charger plugged in while standing in a bath of water with the taps on (where the water may well have a path to earth) could be very problematic with a poor charger design (but this is no longer a +5V problem).

Get a new charger or replace the cable. It is not worth the risk no matter how low the risk is.
...and put your cellphone on the nightstand for goodness sake....

You might also read this Q/A.

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  • \$\begingroup\$ Thank you for taking your time and answering in a detailed way. I didn't necessarily mean being killed by having contact with a frayed cable as, well I'm still alive:) I was just worried about any long term effect... There is just something that I don't understand. On my charger it's written ( output: 5.0V=2700mA/9.0V=1800mA/12.0V=1350mA ) isn't it just too much? According to Google and your diagram 0.2 mA can be deadly... And I do want to buy another cable but the thing is in my country at least 95% of cables are fake, yet they are sold as original. \$\endgroup\$ – Draku Jun 21 '19 at 16:26
  • \$\begingroup\$ @Draku The current rating of the charger is irrelevant. The voltage however is important. In the case your cellphone it is unlikely that the charger negotiates 9 or 12V since the cellphone is a single LiPo cell. If however you were attached to a tablet or laptop that negotiated a higher voltage ….then this higher voltage would impact how much current flowed through a person. Higher voltage ...higher current. Fake cables being a problem is a separate issue. \$\endgroup\$ – Jack Creasey Jun 21 '19 at 18:29
  • \$\begingroup\$ Ok I think I understand by now. Even if I got electrified, the flow would be 5 (Voltage) ÷ 100000 ( the skin resistance ) = 0.00005A or 0.05 mA witch is almost nothing I guess. \$\endgroup\$ – Draku Jun 22 '19 at 6:51

Being exposed to 5V for extended times is absolutely harmless. Nothing to worry about.

However, you should still replace the cable. A frayed cable can create partial for full shorts and these can damage the charger or the phone and result in things overheating or breaking. The cable connector itself could get hot too.

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