Wall wart myth?

[Volvo farmer]

Ok, so I just got a new cellphone, and it reminded me to unplug the charger from the wall when I was not using it. Being the energy conscious type of guy that I am, we measured our cellphone chargers with a kill-a-watt years ago and found that even plugged in, to a fully charged phone, or no phone, they used less watts than the kill-a-watt can measure, which is basically less than 1 watt. Sure they use power when charging a battery, but that's thermodynamics for ya.

The Trimetric on the wall measures amps out of the battery to the 1/10th amp at 24V and doesn't budge whether or not the chargers are plugged in or not. We've just gotten into the habit of leaving the wall warts plugged in, since unloaded, I cannot seem to measure their energy consumption.

So sure, I understand that a device with a constant load and a wall wart is going to draw some phantom power.. Something like a telephone answering machine or a DSL modem might apply, but I'll be danged if I can find a real reason to unplug unloaded wall warts to save electricity.

[Janne]

It depends also on the type of wall wart used. If you leave an old transformer type wart plugged in, it will get quite warm even unloaded. However, the modern switcher type warts don't seem to be consuming too much power when plugged in unloaded.

[ghurd]

I agree.

I tested my cell phone and charger, about 3 cell phones ago, with a 12V 140W 'Freedom Jazz' inverter(?).

The Wall Wart was the 'old' transformer type.

From memory, Grain of Salt,

The inverter used 100ma just being On.  Not 99 or 101, but 100, which I found strange.

Seems like-

The inverter and unloaded wall wart pulled 110ma.

The inverter, wall wart, and fully charged phone (with it's light on saying 'charge complete') pulled 115 or 120ma.

The inverter, wall wart, and 2/3rds dead phone pulled a few hundred ma, which quickly ramped down to the 250ma range, and decreased with time.

Going with the 10:1 / 120V:12V idea, and the wall wart adding 10ma at 12V, or 1ma at 120V.

The transformer wall warts get a lot warmer with MSW, leading to they waste more power on MSW than true SW.  Leading to they don't waste all that much plugged into the wall.

Remember this was the old inefficient transformer wall wart.

The new ones are all much more efficient switchers (electronics are cheaper than copper).

Probably have to test a few switchers, grid fed or TSW, with an AC mA meter.

Crap.  Now I have to do it, but later.  I will post results if you are interested.

G-

[PaulJ]

   Switchmode power supplies don't like being run unloaded; the issue isn't power consumption, it's smoking the wall wart. If it has an indicator LED you're fine, that's enough of a load to keep them happy, otherwise don't run them unloaded (experience speaking here).

   Paul.

[Junkie]

I seriously doubt any smps will release it's precious blue smoke if you leave it just plugged in (not charging, loaded). I've had many many left unloaded for long periods of time, no ill effects.

What happened to your smps ?

[ghurd]

Testing done,

http://www.fieldlines.com/story/2010/2/7/115540/5038

G-

[tecker]

Most resistive and some inductive devices can be run through a diode cap circuit to return the some of the power to a battery bank in fact it woork well for heaters .The wall worts of with small output secondarys should work .Ineed to try some to make sure.