# Does your charger consume power when not charging



## Derick (25/9/14)

Got this excellent answer from Reddit
_The switch-mode power supply in the typical cell phone charger will use on the order of tens of milliwatts no matter what, because they are not perfectly efficient, and will constantly use some power to keep themselves switching when plugged in, providing the DC power your phone needs. Note that cheaper knockoff chargers, in addition to providing poor quality of power for your phone and being generally unsafe, can often be designed less efficiently than a branded charger and thus have a higher vampiric draw.

At the slightly above-average estimate of $0.20/kWh, using the upper bound of 0.100 watts, you can expect to pay a max of about $0.1753/year if you just leave an idle charger running. (If you want to check my math, $0.20/kWh = $0.0002/Wh => 0.100 W * $0.0002/Wh = $0.00002/hr => 8765.81 hrs/yr * $0.00002/hr = $0.1753/yr)

If it takes you 5 seconds to plug and 5 seconds to unplug your charger, for instance, you're spending just over an hour on this task every year. If we value your time at the US federal minimum wage of $7.25/hr, you're using ~4100% more time than it's worth.

So, in short, yes. You're wasting your time._

Reactions: Like 2 | Agree 2 | Winner 1 | Funny 1 | Informative 1


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## Andre (25/9/14)

Been wondering about that as my Intellicharger's plug is at a really awkward place to unplug or switch off all the time. So, seems the blue light can stay on. Thanks.


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## Jan (25/9/14)

Math seems about right for what the blue led would consume I am not sure about what the transformer consume in standby mode?
Any experts???


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## zadiac (25/9/14)

Same as my 5W LED flood lights around my place. I leave them on so I never forget to switch them on when I leave. Don't even notice it on my electric bill.
They're only 5W each, but they light up the whole place all around. Love those lights.


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## Derick (25/9/14)

Jan said:


> Math seems about right for what the blue led would consume I am not sure about what the transformer consume in standby mode?
> Any experts???


It's going to depend on the design. A good design will only pass current to the transformer if there is a load

Reactions: Agree 1


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## Silver (25/9/14)

Derick said:


> Got this excellent answer from Reddit
> _The switch-mode power supply in the typical cell phone charger will use on the order of tens of milliwatts no matter what, because they are not perfectly efficient, and will constantly use some power to keep themselves switching when plugged in, providing the DC power your phone needs. Note that cheaper knockoff chargers, in addition to providing poor quality of power for your phone and being generally unsafe, can often be designed less efficiently than a branded charger and thus have a higher vampiric draw.
> 
> At the slightly above-average estimate of $0.20/kWh, using the upper bound of 0.100 watts, you can expect to pay a max of about $0.1753/year if you just leave an idle charger running. (If you want to check my math, $0.20/kWh = $0.0002/Wh => 0.100 W * $0.0002/Wh = $0.00002/hr => 8765.81 hrs/yr * $0.00002/hr = $0.1753/yr)
> ...



@Derick, that was brilliant! Thank you


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## johan (26/9/14)

Jan said:


> Math seems about right for what the blue led would consume I am not sure about what the transformer consume in standby mode?
> Any experts???



They are all designed in a switch mode topology configuration, and therefore the high frequency ferrite transformer consumes zero energy if there is no load connected as @Derick said.

Reactions: Thanks 2


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## Derick (26/9/14)

johan said:


> They are all designed in a switch mode topology configuration, and therefore the high frequency ferrite transformer consumes zero energy if there is no load connected as @Derick said.


Cool

Arent some transformers just burning off the excess current as heat, or am I talking really old design here?


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## Marzuq (26/9/14)

Derick said:


> Got this excellent answer from Reddit
> _The switch-mode power supply in the typical cell phone charger will use on the order of tens of milliwatts no matter what, because they are not perfectly efficient, and will constantly use some power to keep themselves switching when plugged in, providing the DC power your phone needs. Note that cheaper knockoff chargers, in addition to providing poor quality of power for your phone and being generally unsafe, can often be designed less efficiently than a branded charger and thus have a higher vampiric draw.
> 
> At the slightly above-average estimate of $0.20/kWh, using the upper bound of 0.100 watts, you can expect to pay a max of about $0.1753/year if you just leave an idle charger running. (If you want to check my math, $0.20/kWh = $0.0002/Wh => 0.100 W * $0.0002/Wh = $0.00002/hr => 8765.81 hrs/yr * $0.00002/hr = $0.1753/yr)
> ...




awesome find @Derick 
this is a question that has crossed my mind all too often. thanks


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## johan (26/9/14)

Derick said:


> Cool
> 
> Arent some transformers just burning off the excess current as heat, or am I talking really old design here?



In flyback mode and hence a current source, the design efficiency is on average over 87%. Current is regulated by the PWM (pulse width modulation) ic on each cycle and will only deliver same as required by load, nothing more. The only heat produced, are in the switching device (Mosfet) and output rectifying diode due to internal on-resistance. Hope that answers your question.

Reactions: Like 1 | Informative 1


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## Derick (26/9/14)

johan said:


> In flyback mode and hence a current source, the design efficiency is on average over 87%. Current is regulated by the PWM (pulse width modulation) ic on each cycle and will only deliver same as required by load, nothing more. The only heat produced, are in the switching device (Mosfet) and output rectifying diode due to internal on-resistance. Hope that answers your question.


Googled a bit and what I was thinking about is called a linear transformer, not a switching one - but yeah, old design and not used anymore (guess I'm showing my age) 
http://www.lifesafetypower.com/tool...ing-ols-switch-mode-and-linear-power-supplies

Reactions: Like 1 | Agree 1


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## Derick (26/9/14)

Derick said:


> Googled a bit and what I was thinking about is called a linear transformer, not a switching one - but yeah, old design and not used anymore (guess I'm showing my age)
> http://www.lifesafetypower.com/tool...ing-ols-switch-mode-and-linear-power-supplies


Did you just agree to me saying that I'm showing my age?

Reactions: Funny 2


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## Silver (26/9/14)

@johan and the other electronic experts.
I have a question somewhat related to this topic.

I have low voltage 12V downlights in my ceiling. Each has one of those little transformers in the ceiling that steps down the 220V to 12V to power the incandescent (old-school) 50W downlighter bulbs. I cannot believe how hot those little box-shaped transformers get. You can't even touch them.

I was considering putting in a few of those 4W LED energy efficient bulbs. A friend "who thinks he knows everything" said to me once that changing the bulbs will not necessarily save any electricity because the transformer will still get hot and use a lot of power. He says it's the transformers that are also at fault and I should lose the transformer altogether and switch to a 220V system for the downlights.

Is he talking nonsense?

If I connect a 4W bulb to my current set up (with the transformer), will it use 4W of power? Or more?

Reactions: Like 1


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## johan (26/9/14)

Silver said:


> @johan and the other electronic experts.
> I have a question somewhat related to this topic.
> 
> I have low voltage 12V downlights in my ceiling. Each has one of those little transformers in the ceiling that steps down the 220V to 12V to power the incandescent (old-school) 50W downlighter bulbs. I cannot believe how hot those little box-shaped transformers get. You can't even touch them.
> ...



No your know-it-all friend is correct. Those transformers are poorly designed with poor core metals (cheap-n-nasty-made-in-a-hell-of-a-hurry-in-china) and the heat buildup is due to excessive Eddy currents. Heat is a sign of losses (waste of energy). If you can replace them with 220V LED's (soft white) and stick to the well known brands like Osram, Philips or GEC, don't buy cheap LED lamps, they are inefficient and loose light intensity within 6 months.

Reactions: Thanks 1 | Informative 2


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## johan (26/9/14)

Derick said:


> Did you just agree to me saying that I'm showing my age?



Apologies Derick I agreed on "Linear Transformer" - hope it makes you feel better

Reactions: Funny 2


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## Silver (26/9/14)

johan said:


> No your know-it-all friend is correct. Those transformers are poorly designed with poor core metals (cheap-n-nasty-made-in-a-hell-of-a-hurry-in-china) and the heat buildup is due to excessive Eddy currents. Heat is a sign of losses (waste of energy). If you can replace them with 220V LED's (soft white) and stick to the well known brands like Osram, Philips or GEC, don't buy cheap LED lamps, they are inefficient and loose light intensity within 6 months.



many thanks @johan

Appreciate the detailed feedback. I will do that in time!

Reactions: Thanks 1


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## johan (26/9/14)

Silver said:


> many thanks @johan
> 
> Appreciate the detailed feedback. I will do that in time!



PS. Those transformers are for the past 5 years banned in USA as well as EU countries due to fire hazard.

Reactions: Like 1


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## Silver (26/9/14)

johan said:


> PS. Those transformers are for the past 5 years banned in USA as well as EU countries due to fire hazard.



I can imagine, thanks @johan - all the more reason to lose them.

Reactions: Like 1


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## Marzuq (26/9/14)

What does this mean wrt to charging overnight. Is it safe for the battery using an intellicharger in this manner or best to remove batteries when fully charged 

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## johan (26/9/14)

@Marzuq you can safely leave your batteries in an intellicharger overnight, the charger will not overcharge batteries as it has a build in charge capacity sensing circuit and accordingly will stop charging the batteries once they are charged to capacity.

Reactions: Like 2


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## Marzuq (26/9/14)

That's great news @johan. Thanks 

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Reactions: Like 1


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