USB Dangers

[polygonum]

How dangerous would it be to use a phone or tablet in the bath whilst it is connected to a mains-powered USB charger?

Obviously it could be dangerous to the device itself if you drop it into the water!

Obviously a 5 volt low current supply isn't usually life threatening.

Obviously we have rules about sockets in bathrooms. But a long USB cable to a socket in another room seems a likely way round that.

But if something is wrong somewhere, such as a mis-wired USB charger, could there be any appreciable danger?

Is there in future likely to be a bathroom-safe USB socket next to the shaver and toothbrush socket?

[tabbypurr]

There is a very thin barrier between mains and usb output. If it breaks down you're fried. A great number of noncompliant chargers exist that have very inadequate insulation. I would not do it.

NT

[polygonum]

I assure you it is not my intention to do it! I expect many people do, though, and it made me wonder. If I did want to, I'd probably think to use my battery pack USB charger or, preferably, charge before bath, but I don't want to drown my phone or tablets.

I was also imagining the next generation of shavers and toothbrushes possibly having USB charging as standard? Or, wireless charging but with the charging plate being fed by USB.

[Andy Burns]

If you look at various USB charger and SMPSU teardowns on youtube, they often have a sizeable fraction of mains voltage (at a minute current) on the 5V outputs, the sort of "tingle" you can feel with an unearthed laptop when it contacts bare skin could feel a lot worse with wet skin in the bath, the leakage current won't directly hurt you, but if it makes you jump you could lose your footing or bash your head on the tiles etc

Just charge the device up in advance of using it in the bathroom?

[Halmyre]

Or, heaven forbid, do without it for half an hour or so? Fair enough if you're reading a book on your Kindle, but not if it's sheer terror at the thought of being 'off the grid' for any length of time.

[Andy Burns]

I know they make a waterproof kobo, but do Amazon make a waterproof kindle? I gather there are 3rd party kindle waterproofers.

[Reentrant]

[dennis]

And yet some of the really cheap Chinese stuff is done well, like the relay board for my arduino. They have routed an air gap around the common pin to separate it from the 5V coil which is at the same end.

It makes you wonder who designs some of the stuff.

[Bill Wright]

Yes! Good grief, there's plenty of other things to do in the bath.

Bill

[Dave Plowman (News)]

Odd, isn't it. Everything must be cordless these days - even when of little benefit. But on the *one* occasion where most would agree cordless is safest - in the bath - someone wants to run a cordless device off mains.

And you wonder why the EU seems to do odd things like labelling salmon as containing fish? ;-)

[polygonum]

I don't want to do it. I don't need to do it. I won't do it. But thoughts arose about charging shavers and toothbrushes, for which USB might be viable, which then led me to consider the worst-case. Which was charging a device, using a crap charger, while in the bath.

The start point in my mind was the need to carry specific chargers for shaver and toothbrush when travelling.

[The Natural Philosopher]

[Bill Wright]

It's all in your mind. Me and my loofah are just good friends.

Bill

[Brian Gaff]

I would ask you this, Have you ever looked inside of a usb charger. Most have no fuse and the switch mode supply is driven directly from the mains via a semiconductor driving the primary of a transformer a very tiny transformer, at a high frequency, the other side is connected to a very simple rectifier and voltage stabilising chip. You are in effect relying on a cheaply made tiny transformer to isolate you from the full mains voltage. I'd no chance it knowing what I know about these things. I have had more than one fail one very spactacularly and trash the device on it. Crap. Brian

[Brian Gaff]

Don't know about that, I've always thought that inductive chargers are pretty inefficient, even if driven at high frequencies. I suppose you could have a bit battery and a cable to your device which would be safer than a mains connection of any kind.

Brian

[polygonum]

Toothbrushes already use an inductive charger - but a proprietary one that typically has plastic "pin" that fits into the body of the brush. I don't think the inefficiencies are going to make much difference overall.

[The Natural Philosopher]

Actually, they are pretty efficient. Especially regulating ones

[F Murtz]

[polygonum]

Both of those involve the charger itself - clearly something not to be done. Relevant but what was in my mind was more the danger even if the USB lead were maximum length and the charger and socket were in another room. Or the charger were specially designed for bathroom use (like a shaver/toothbrush socket) - that is, assuming it is possible to design one that is safe.

[ARW]

Fitted 12 last week.