Mobile Phone Chargers - Expensive to Run ?

Southern Electric (UK Energy supplier) have sent me a leaflet urging me to use less of their product (electricity).

In it they state:

"Unplug your mobile phone charger - these little black boxes suck 100kWhrs (sic) from your socket, even when the phone is fully charged"

Am I correct in thinking that is one hundred, thousand Watts per hour ? I didn't think it was quite that much but perhaps might explain why my electricity bills are so high ?

If a 'unit' of their electricity (1000 Watts for one hour) costs about 10 pence, then each day I am paying 24 x 100,000 x 10p = £240,000 per day. Wow !

Am I missing something here ?

--
Mike Meakin
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Mike Meakin
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In article , snipped-for-privacy@nikam.freeserve.co.uk (known to some as Mike Meakin) scribed...

:splorrf!:

If your mobile phone uses a battery pack the size of your car, then they might be correct.

Outside of that: A typical mobile phone charger pulls less than 100 milliamps when idle, and probably not much more than 200-300 or so when charging the phone.

Assuming your line voltage is 220VAC nominal, and assuming a 50mA idle draw, AND applying Ohm's Law as in P(watts) being equal to I (current) times V(voltage), we come up with the following:

Idle: 0.050 x 220 = 11 watts. Charging (worst case): 0.300 x 220 = 66 watts (and frankly, I doubt it's even that high).

For Kilowatt-hours, given that 1kWh is equal to 1,000 watts, we do this: 66 watts times 1 hour means 0.066kWh, absolute worst case (and assuming I got my decimal points in the right place), when charging.

Keep in mind that my numbers completely ignore inductive reactance, and are probably inflated. I've not taken the time to do any actual measuring of what a mobile phone charger draws.

HOWEVER -- I think whoever wrote that pamphlett needs a serious review of basic math and electrical principles. I also think that if your electric bill has suddenly increased, you need to double-check how many lights you're leaving on. ;-)

Keep the peace(es).

--
Dr. Anton T. Squeegee, Director, Dutch Surrealist Plumbing Institute
(Known to some as Bruce Lane, KC7GR)
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Reply to
Dr. Anton T. Squeegee

Only if you count world wide. And you get all of the power as heat which is nice right now.

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Homer J Simpson
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o
s

ay. Wow

Hee hee hee. I think your initial mistake is confusing the meaning of=20 "100kW-hrs". Not 100 kW *PER* hour, but more likely 100 kW-hrs in=20 total over the expected lifespan of the charger. (=3D100 x 10p =3D 10=20 pounds.) You'd need to have quite a few kettles continually on the boil=20 to achieve a figure of 100 kW per hour.

But one thing's for sure - these damn wall-warts do continue to suck power= =20 from the mains, even while they're not doing anything useful - like=20 recharging spent batteries - so the advice is sensible; always unplug=20 the buggers when they're not actualy being used. As overheating=20 wall-warts are an increasingly common cause of house fires, it makes sense= =20 from a safety point of view too.

Cheers, Pete.

Reply to
Pete Wilcox

100kWhrs

Wow

Yes you are failing to read it properly. All the phone chargers that people leave plugged in draw 100s of KWh unnecessarily. Possibly a watt or so for each one.

Reply to
Bob Minchin

The information you have is not accurate. Mobile phone chargers are very efficient. They pull about 10 to about 30 mw (milliwatts) when at idle. This is less than the average AC line operated table top alarm clock. When charging a mobile phone battery, they can pull up to about 150 to 200 mw maximum. After the battery is charged, the charger goes to an equalization state to keep the battery topped up. In the equalization state, this also avoids over-charging the battery.

If you read the electrical specification on the label on the charger unit, it should indicate the maximum possible current it can pull in the worse case possible.

1 mw = 0.001 Watt 100 mw = 0.10 Watt
--
JANA
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Reply to
JANA

Thank you all for your replies.

That makes much more sense. I just quoted what was in the leaflet and thought that I had misunderstood the meaning of the units.

So perhaps 100mW per hour (max) rather than 100kW per hour, so out by a factor of a million ?

Or perhaps 100kW per hour for all the UK phone chargers (say a million)

Reply to
Mike Meakin

Many of the older iron-core transformer ones get noticeably warm, even when not charging anything. These will use around a watt I suppose. A watt * a year = 8 KWh, which would come around 80 p or a bit above a euro - depending on cost and taxation.

The Netherlands has an energy tax that nearly doubles the cost of electricity, but also gives back 190 euro to pay this tax from. On my bill the energy tax is a net win, though my incremental energy costs are higher than they would be without tax. Which makes saving make sense.

My charger says 20 mA, x 230 volts = 2.6 watts. But this is inductive, and won't be the real power.

In any case, the modern electronic lightweight switcher chargers use very little power when idle. My laptop power brick claims less than half a watt, and that is a 65 watt output brick.

Thomas

Reply to
Zak

Sorry but you are wrong this time.

Many chargers use more than a Watt when not connected to a phone, and just about all of them use more than a watt when charging. Read the information printed on your charger if you don't believe this.

Perhaps you are confused between milliwatts and milliamps.

Chris

Reply to
Chris Jones

I too had such a leaflet- I wrote to Southern Electric, pointing out (amount other things) that it implied >4kW into the charger, and that a UK (240v, 13A) socket can only supply some 3.1kW.

To their credit, they sent me a courteous reply, the nub of which was: " I think the ink on the first batch of promotional leaflets was still wet when a circular came round to warn us advisers of the impending complaints as a result of that little "k".

We have since taken the steps to resolve this issue. "

-- Per ardua ad nauseam

Reply to
tersono

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