Thinkpads Forum

Since I'm always rather lazy with plugging out the adapter from the mains when I go away with my TP and I don't take the adapter with me, my Question would be:

Does the AC-adapter pull power from the mains when the ThinkPad is not connected to it?

Does the Mini-Dock (or other portreps) use any power without the ThinkPad?

Has anyone ever messured it?

I've already tryed searching without success, so if this was already a topic a link would do.

Thanks.

Any power brick or similar device will pull a small amount of current anytime it is plugged in.

It's a tiny fraction of what it uses when it's powering your TP, but as has often been pointed out if you add up all the things that people leave plugged in all the time it's enough to power a small city.

Ed Gibbs

Yes, I just as I thought.

The exact amount would be interresting to know.

Am I right in suspecting the TP adapter are of the switching power supply type, as opposed to transformers?

I mean with them being autosensing and stuff like that, I was hoping that they shouldn't need to much power to run when unplugged from the ThinkPad.

Yes, they are switchers, and I think typically it is in the couple hunderd milliwatt range. It's not significant until you consider the billions of similar devices plugged in around the world.

Ed Gibbs

It is possible to measure the AC current draw with a meter.

There are adapters that separate the two current paths between the plug and the receptacle so that you can clamp a meter around one side and read the current. Both sides will be the same, of course.

See your local home store for meter and adapter.

Yes I know its possible, i just havent got the necessary hardware. (clamps for reading current)

There are also special meters that goes in between the adapter and the mains-plug, wich messures the used power directly. I just thought maybe someone has one or has already try'd.

That's a good question. I will try to remember when I get home, to hook mine up and quantify it.

I can't recommend strongly enough though that more people buy a Kill-a-Watt or Watts Up? meter. They are quite useful for measuring real power usage of any appliance, and gives you numbers that allow you to rationally prioritize energy-saving efforts.

Follow-up. I connect my "Watts Up?" device to a common Thinkpad 16-volt adapter. I get a reading of 0 Watts. I changed mode to the KWh setting and left it that way for a while. This mode would show you if you left it on for X hours for example, the total KWh used by a device that cycles on and off, and it remained zero.

So if it's using power without a laptop attached, it's an amount below my ability to measure with this cheap device.

Great, thank you!

Just out of interrest, could you see how much power is used when the ThinkPad is in Standby-mode?

On my T-60, I get the following measurements:

1) Power adapter unplugged from PC or PC in standby mode: .1 amps at 120 volts

2) PC on, not doing anything in particular: 2.2 - 2.4 amps, in line with the label on the adapter.

So, it draws less than 5% of the power when not connected or in standby as opposed to the power-on state.

0.1 amps X 120 volts = 12 watts base draw

2.4 amps X 120 volts = 288 watts in

4.5 amps X 20 volts = 90 watts out

Wow, thats a lot

Thats definetly got me taking them things from the mains when not used.

I don't think an adapter draws 300 watts from the mains. Mine certainly does not (I checked).

Try a test: Find a 300 watt light bulb and put it in a socket with a plug. Plug in somewhat slowly to an outlet. Watch the arc.

Try the same test with an adapter. It won't arc like that. Mine certainly does not.

My adapter says 1.4 amps under load at low mains and 0.7 amps under load at high mains. Then my machine is rarely drawing full load. So even now, if I unplug and plug back in, (wait a second ............ ) there is no arc. 300 watts draws an arc in my experience. ... JDH

A 300 watt light bulb? That must be bright!
I've never seen a normal bulb over 60 watts.

Anyway, its not not the power the Thinkpad pulls, I'm concerned about (If I want to use it I will), but the power that the the adapter uses without Thinkpad, which would just be wasted.
Not only is it bad for the environment (or so they say ), but here in Germany we have to pay for every kwh we use, so little apliances as adapters and other aplicatios on standy really add up to quite a bit of money.

I don't get an arc either from my apapter.
My 350 watt desktop on the other hand does sometimes arc.

DarkMark wrote:A 300 watt light bulb? That must be bright!
I've never seen a normal bulb over 60 watts.

Yes, it will be bright. Tri-lights go up to 300 watts. Big, Hot, Bright and must be used with care. ... JDH