Why does my electricity go the wrong way?

February 28, 2007 2:11 PM

Why does my electricity go the wrong way?

This sounds weird, but I swear I'm not making this up.

If I try and charge my cellphone, camera or mp3 player from the power strip in my office, the battery levels go down.

A few weeks ago I plugged in my Samsung D500 phone through the OEM charger and I watched the battery level indicator fall. Then today I plugged in my Creative Zen as soon as the low battery warning came on and it suddenly died and started blinking a single blue light at me.

Back at home, I plug them in to the power strip in our study and both of them start charging normally (although the zen decided it needed to rebuild its system).

Both home and office are 230v AC power. What the hell is going on?

posted by talitha_kumi to technology (12 comments total)

Do other appliances work with the office power strip?
posted by Krrrlson at 2:18 PM on February 28, 2007

The only other things on the strip are my monitor, the pc tower (same thing happens if I try and power off the usb supply) and an ancient PDA that powers down as soon as it comes off the cradle.
posted by talitha_kumi at 2:20 PM on February 28, 2007

What do you mean by "same thing happens if I try and power off the USB supply?" As in, USB devices cannot be powered from the PC?

I would suspect a short either in the power strip or one of the devices connected to it. Just unplug the tower and monitor next time you're in and see if the same behaviour occurs when using the strip alone -- then you'll know who's to blame. Make sure you check different outlets in the strip.
posted by Krrrlson at 2:41 PM on February 28, 2007

Sorry.. I'll rephrase it.

The monitor and PC both work fine. Charging my phone or zen from the power strip or via the 5v output on the usb ports of my computer both cause the devices to drain.

I use the same cables at work and at home, so it's not a short inside that side of things. A short in the power strip should be killing the pc and/or tripping the rcds on the fusebox, shouldn't it?
posted by talitha_kumi at 2:48 PM on February 28, 2007

Given that the USB ports on your PC are behaving in the same way, it's probably the PC after all. See if unplugging the PC "fixes" the power strip.

(As for shorts, they'll only blow fuses if you're actually shorting the power lines together. It's possible to imagine a situation, however unlikely, of your devices being shorted to some undesirable current sink, but not actually being connected to both of the power lines.)
posted by Krrrlson at 3:04 PM on February 28, 2007

not sure if this is helpful, but i have a plug in my home that has the polarity reversed. the home inspector found it, and i verified it with a cheap reader i purchased at the hardware store.

the plug seems to work ok, but when i plugged a power supply for a wireless phone, it fried it.

maybe that's your problem? try getting a polarity checker at the hardware store. i'd offer you mine, but it seems a bit far to walk to borrow a tool.
posted by lester's sock puppet at 3:45 PM on February 28, 2007

AC doesn't have any "polarity". ("Hot" and "common" can be swapped if the receptacle is miswired, but that has nothing to do with polarity.)

Power supplies can't run backwards.

Chargeable devices have protective diodes that prevent energy from flowing out instead of in.
posted by Steven C. Den Beste at 4:00 PM on February 28, 2007

Some modern batteries charge up by first doing a discharge, and then charging up the battery. Is it possible that you're seeing the discharge cycle first?

Also, make sure that there's sufficient power being supplied so that the charge cycle can start...
posted by Arthur Dent at 4:18 PM on February 28, 2007

you're not using a replacement radio shack ac adaptor are you? when you put the correct adaptor on the end you have to make sure the tip polarity is correct. i fried the charging circuit of an old mp3 player by getting it reversed. if it's an original charger, this couldn't be the problem though.
posted by noloveforned at 6:49 AM on March 1, 2007

You're having problems on both sides of the PC's rectifier? One at the USB port and one at the electrical mains?

There's something else wrong.
posted by cmiller at 7:22 AM on March 1, 2007

A lot of modern power adapters for things like cell phones will detect a poor-quality AC power source (be it overvoltage, the wrong frequency, noise, etc.) and refuse to charge. A computer, lamp, or other less finicky device could work fine in an outlet that doesn't meet their standards.

So you've got bad power, somehow. I doubt it's making your devices "uncharge" but it's certainly not charging them.

Start by replacing the power strip. Better yet, remove it entirely and plug your devices straight into the outlet. If that fixes it... bad power strip. If you still have trouble... call an electrician.

P.S. If this is bad enough to affect the power coming out of your USB ports, unplug that computer and monitor! It's only a matter of time before the power problem affects them.

One more note: Assuming your building power is noisy or otherwise bad, one potential fix is to buy a UPS (uninterruptible power supply), plug it into the mains, and plug your devices into it. That will give them clean power and also insulate them from damage due to whatever problem may exist. A decent one will cost your local equivalent of US $40 or so.
posted by mmoncur at 2:59 AM on March 2, 2007

Hi guys... I'm (effectively) the OP - my wife posted for me.

The devices definitely aren't draining before charging - they're liOn batteries and they charge straight away elsewhere.

The charger is a motorola charger for a bluetooth earpiece that charges via the same micro usb connector that my phone and Zen use.

The 'bad power' idea sounds plausible. As does the crappy pc concept since my sound card has just managed another exciting trick - converting all outgoing sound to mono with the left channel being subtracted from the right to create a weird kareoke style effect. Which is fun.

I'll try the power strip and check back later. Cheers guys.
posted by twine42 at 2:05 PM on March 4, 2007