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blackrose

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The H&S person at work sent us this today, which applies equally to boats I suppose. Unfortunately the pictures of the house fire don't want to paste and it seems quite difficult to post a MS Word document on here, but anyway there's a picture of the aftermath of a house fire caused by an overheating phone charger.

The thing is that I see no power draw on my 12v battery monitor when my phone charger is left plugged in (on the inverter) until I connect the phone, so is the warning technically correct? 

Key Safety Tip

Never leave phone chargers switched on when not charging – at home or work

The science behind the fire:

Chargers are constantly drawing power, though not as much as they would if they were plugged into the device. Left plugged in without connection to a device could lead to a risk of fire either through heat build-up or a short circuit.

The risk results from the way chargers extract their power. Chargers convert alternating current (AC), to direct current (DC) from the plug socket using transformer circuits. These consist of two coils, one small and one large that loop around and use an electromagnetic field to influence each other. When you unplug your electronic device from the charger, this breaks the circuit on the smaller coil, but the larger coil continues to move electrons. This causes power to leak into the charger even if it is not connected to any device. Power can also be drawn out if there is an LED present in the charger, as this causes more resistance.

While pulling power does not cause an immediate danger, the side effects could be enough to cause a spark. If there happens to be enough water or moisture in the air, it can short-circuit the transformer. During a short circuit, abnormal connections within the circuit cause an excessive amount of current to pass through the charger, which overheats the circuits and could potentially start a fire.

Apart from wasting energy, leaving electrical items on standby increases fire risk.

Unless necessary, please switch off all plug sockets before leaving work

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We have a generic usb socket wired direct to the fuse box. It will take 2 usb and when I bought it I checked its maximum output was safe for a tablet 2.1 and phone, simultaneously. It wasn't a cheap Chinese thing ( or so I thought) having all the relevant standards. Started smouldering last year when iPad plugged in after about 2 years service. Fuse did not go, fortunately I smelt it and disconnected the line quickly. We used to leave it on when we boated ... Tablets seem to draw lots of power (well2.1 amps through crapy bits of Chinese electrics.

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56 minutes ago, blackrose said:

The H&S person at work sent us this today, which applies equally to boats I suppose. Unfortunately the pictures of the house fire don't want to paste and it seems quite difficult to post a MS Word document on here, but anyway there's a picture of the aftermath of a house fire caused by an overheating phone charger.

The thing is that I see no power draw on my 12v battery monitor when my phone charger is left plugged in (on the inverter) until I connect the phone, so is the warning technically correct? 

Key Safety Tip

Never leave phone chargers switched on when not charging – at home or work

 

 

The science behind the fire:

Chargers are constantly drawing power, though not as much as they would if they were plugged into the device. Left plugged in without connection to a device could lead to a risk of fire either through heat build-up or a short circuit.

The risk results from the way chargers extract their power. Chargers convert alternating current (AC), to direct current (DC) from the plug socket using transformer circuits. These consist of two coils, one small and one large that loop around and use an electromagnetic field to influence each other. When you unplug your electronic device from the charger, this breaks the circuit on the smaller coil, but the larger coil continues to move electrons. This causes power to leak into the charger even if it is not connected to any device. Power can also be drawn out if there is an LED present in the charger, as this causes more resistance.

While pulling power does not cause an immediate danger, the side effects could be enough to cause a spark. If there happens to be enough water or moisture in the air, it can short-circuit the transformer. During a short circuit, abnormal connections within the circuit cause an excessive amount of current to pass through the charger, which overheats the circuits and could potentially start a fire.

Apart from wasting energy, leaving electrical items on standby increases fire risk.

Unless necessary, please switch off all plug sockets before leaving work

I dont think many have 2 coils round a lump of iron any more so that would make me doubt the whole piece.

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Forwarned is forarmed. Thanks for all safety reminders. Its up to the individual how seriously he judges it.    Terrible in retrospect to cry  ' I didnt think it could happen to me ! '.   It didnt.   It happened to your wife, kids, old granny and the dog whilst you were down the pub  ! Take it serously please.

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18 minutes ago, Iain_S said:

The advice is aimed at 240V mains chargers, as the 12V ones don't use a transformer.

Our household 240V ones get warm, whether or not there is anything plugged in to them

My laptop chargers get warm but my mains phone charger doesn't and doesn't seem to draw any power.

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13 minutes ago, Irob said:

Forwarned is forarmed. Thanks for all safety reminders. Its up to the individual how seriously he judges it.    Terrible in retrospect to cry  ' I didnt think it could happen to me ! '.   It didnt.   It happened to your wife, kids, old granny and the dog whilst you were down the pub  ! Take it serously please.

Unplug the TV, Microwave, Sky box, Answer Phone, Digital Time clocks, washing machine, computer, printer, router, wireless telephones.  Where does it end, just think what you leave plugged in and live while you are out.

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8 minutes ago, ditchcrawler said:

Unplug the TV, Microwave, Sky box, Answer Phone, Digital Time clocks, washing machine, computer, printer, router, wireless telephones.  Where does it end, just think what you leave plugged in and live while you are out.

I have to confess I have a list as long as that of things I leave plugged in to mains (and with the wall switch on) in my house, even when I go away for a week or two boating. My theory is that as I had a proper electrician check all my wiring and install a modern RCD box when I moved in 8 years ago (the old setup was well dodgy) the risk should be very low, but am I being complacent?

Rather than go round pulling out plugs, some of which are awkward to get at, perhaps I should turn all my power off under the stairs when I go away for more than the odd day, as most of my stuff would reset itself when power came back on? The Virgin TV box takes perhaps 10 minutes to sort itself out, the computer's modem/router less than that, and the computer would be shut down first anyway and just has to catch up afterwards on automatic updates for Windows and antivirus software. In theory I think the only thing I'd have to reset myself would be the clock on my electric oven!

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Good posts and good to remind everyone. Genuine question though, a few years ago if you wanted to buy whatever product you could always buy at different prices and know you were getting differing qualities. However today when all leccy stuff is seemingly knocked out in China/Vietnam etc etc just HOW can you assure you are buying decent stuff as it doesn't always follow now does it that price is key?

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22 minutes ago, Peter X said:

I have to confess I have a list as long as that of things I leave plugged in to mains (and with the wall switch on) in my house, even when I go away for a week or two boating. My theory is that as I had a proper electrician check all my wiring and install a modern RCD box when I moved in 8 years ago (the old setup was well dodgy) the risk should be very low, but am I being complacent?

Rather than go round pulling out plugs, some of which are awkward to get at, perhaps I should turn all my power off under the stairs when I go away for more than the odd day, as most of my stuff would reset itself when power came back on? The Virgin TV box takes perhaps 10 minutes to sort itself out, the computer's modem/router less than that, and the computer would be shut down first anyway and just has to catch up afterwards on automatic updates for Windows and antivirus software. In theory I think the only thing I'd have to reset myself would be the clock on my electric oven!

I always turn the computer,router, printer off when we go away and also unplug the phone line from the router, that is after having one fry in a thunderstorm. When at home I do the same if there is a storm. A neighbour had a deep freeze fail after problems with the overhead cables putting a high voltage live to neutral, that time I lost the router power supply and the telephone base set.

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35 minutes ago, Peter X said:

I have to confess I have a list as long as that of things I leave plugged in to mains (and with the wall switch on) in my house, even when I go away for a week or two boating. My theory is that as I had a proper electrician check all my wiring and install a modern RCD box when I moved in 8 years ago (the old setup was well dodgy) the risk should be very low, but am I being complacent?

Rather than go round pulling out plugs, some of which are awkward to get at, perhaps I should turn all my power off under the stairs when I go away for more than the odd day, as most of my stuff would reset itself when power came back on? The Virgin TV box takes perhaps 10 minutes to sort itself out, the computer's modem/router less than that, and the computer would be shut down first anyway and just has to catch up afterwards on automatic updates for Windows and antivirus software. In theory I think the only thing I'd have to reset myself would be the clock on my electric oven!

And replace all of the stuff in the fridge and freezer that had spoilt :rolleyes:

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2 hours ago, Naughty Cal said:

And replace all of the stuff in the fridge and freezer that had spoilt :rolleyes:

That would be the main snag to my plan, I already run down my fridge contents before going away, but to put the power off I'd have to plan to use up everything in the freezer, or persuade a friend/relative/neighbour to store what's left.

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Interesting debunking piece here: http://www.lifehack.org/articles/technology/5-myths-about-phone-charging-debunked.html

Main points are to be safe, don't use cheapo clone chargers and be aware of the heating issues, so don't leave the phone or tablet lying on readily flammable surfaces like paper or your bedding. Purpose designed chargers for your phone/tablet have good charge controls that shut down the charger as the battery reaches full charge.

I don't believe the stuff about transformers – surely all modern chargers are switch mode these days? They're just not heavy enough to contain iron cores.

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Unfortunately because the technical parts are such complete bollox I can’t take the article seriously at all and suggest the article does more harm than good -it’s full of nonsense. 

Blackrose might be worth suggesting your elfin safety fella not distribute this sort of clap trap as is it just brings everything he says into disrepute and one day he will have something important to pass on...

 

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10 minutes ago, jonathanA said:

Unfortunately because the technical parts are such complete bollox I can’t take the article seriously at all and suggest the article does more harm than good -it’s full of nonsense. 

Blackrose might be worth suggesting your elfin safety fella not distribute this sort of clap trap as is it just brings everything he says into disrepute and one day he will have something important to pass on...

 

No I won't tell him not to distribute this stuff because as Andrew says: The advice is good. The "explanation" is rubbish. 

And since he's mainly concerned about the advice rather than the technical explanation it doesn't bring the advice into disrepute. 

However, I will tell him that the technical explanation is wrong.  

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If it is so dangerous to leave a charger plugged in when not in use, how come they can sell mains sockets with built-in always-on USB charging connectors?

It's like the oft repeated comments that leaving your TV on standby overnight will cost £££ per year (insert made up number, typically 20 or 30). My TV takes 0.1 watt on standby which is less than 1 unit of electricity per year, which is not all that unusual, and yet the myth of high consumption is constantly peddled. Of course maybe the TV will catch fire but that's a different story.

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2 hours ago, jds_1981 said:

Generally good idea but to unplug things very marginal risk reduction).

The document appears to come from this random internet site https://itstillworks.com/leaving-chargers-plugged-increase-risk-fire-12305415.html

As a rule, I tend to be very cynical about badly written warnings on the internet.

This^^^

I thought about doing some research to compare how many of the tens of thousands (at least) of phones and tablets in use in the U.K. have caused fires with how many fridges, freezers and tumble driers have done so, but decided it wasn't worth it.

Life is full of trivial risks, get over it.

ETA: silly me, it's at least 37 million smartphones alone, almost all of which will be recharged every day!

Edited by BruceinSanity
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9 minutes ago, BruceinSanity said:

This^^^

I thought about doing some research to compare how many of the tens of thousands (at least) of phones and tablets in use in the U.K. have caused fires with how many fridges, freezers and tumble driers have done so, but decided it wasn't worth it.

Life is full of trivial risks, get over it.

ETA: silly me, it's at least 37 million smartphones alone, almost all of which will be recharged every day!

And what is suspected of starting the Grenfell Tower fire

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1 hour ago, ditchcrawler said:

And what is suspected of starting the Grenfell Tower fire

Exactly. Apparently fridge freezers account for 7% of electric fires in London, and there are a lot fewer of them than smartphones.

I'm not advocating abandoning common sense here, just trying to keep a sense of proportion. Leaving your phone on your pillow or buried under papers on the desk whilst charging isn't wise, clearly. Most of the "fires started by chargers" stories I've found involve either that sort of unwisdom or else using a cheap clone charger.

One of my Apple chargers is showing its age by stopping charging prematurely (it's a bad habit they have) and I note that the replacement I'm planning to get specifically claims that it has overtemp and overcharge cutouts: https://www.amazon.co.uk/gp/product/B0793JMKGH/ref=ox_sc_act_title_1?smid=A9QYG3W21ZOKC&psc=1

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