recharger power consumption

We have several rechargers (for mobile phones and torches) which are permanently plugged in and switched on, and the phones/torches are attached whenever they need recharging.

I'd assumed that the rechargers would use a negligable amount of power when a phone or torch was NOT attached. Howevever as there are 5 of them and they are "on" 24/7 I'd like to find out how much power they are using (and the cost!) when in use and more importantly when NOT in use.

For example, one mobile phone charger is rated as

Input: 100-240V ~ 50/60Hz 0.1A Output: 5.9V 375mA

Actually I'm not sure what figures here tell me what it's power consumption is either when recharging or with no phone attached. Can anyone clarify this for me?

Reply to
cbdeja
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The nameplate is maximum / worst case.

Reply to
Homer J Simpson

The figures they state are usually "worst case" the bottom end of the specification (most power consumed)

You can't predict the cost of operation accurately, based on just the nameplate ratings or even measuring current and voltage and computing watts. And your power company's billing criteria may further complicate reaching a meaningful answer.

If something is using a couple of watts, when it is off, the cost to me is ~$15 a year - for that amount, and depending on how often I use it, I'll usually put in a switch or unplug it to turn off the power. The switch pays for itself.

If the case gets warm when it is off - its a good candidate for a switch - in my opinion. Warm means you have some proof it is dissipating power - and it is subjective and inaccurate . . .

Large items like microwaves, VCRs, TVs, Audio systems are impossible to judge with just the feel test - the case is large with respect to the power so the temperature rise isn't noticeable. I went around with a voltmeter and ammeter and measured everything I use, on and off, put the numbers in a spreadsheet and calculated out the costs - not accurate, but better than nothing.

A switch on the water heater so you can turn if off when not in use or you're on vacation would probably do more to lower the bill than any

50 battery chargers. I have a neon light that indicates the water heater is turned on, and an LED to indicate it is actually heating water. 25% of my usage evaporated with just hot water conservation.

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Reply to
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Thanks for the comments.

So in the above, the max consumption would be

240 * 0.1 = 24 Watts

Although even when recharging a battery it may actually be less than this.

And when nothing is attached .... the only thing you can be sure of is that it will be less than that!

I th> >

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Reply to
colin.browell

Yes

yes

Yeah, it is probably wiser to leave them plugged in and eat the loss.

The newer crop of solid state switcher supplies are much more efficient and draw virtually no power when it isn't needed - the kind appearing on cell phone rechargers today. They make them in an assortment of output voltages - but they won't necessarily work with the old style battery chargers - sometimes a lossy transformer is part of the charging scheme - automatically limits the current.

The price of copper will drive out the old style transformers.

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