Curious Find Inside AC to USB Adapter- A Coin Cell

Thread Starter

PGB1

Joined Jan 15, 2013
139
I decided that experimenting with this charger was way more important than cutting the lawn, painting the soffits, doing brick repairs on the chimney & stuff like that, so...

I de-soldered enough to get the battery out of a couple of units for some science project time. They do, indeed, work without the battery. Curiously the relay in just one of them clicks in & out while the unit is plugged in. The output voltage remains steady while it's clicking. I didn't dive in to that mystery (yet).

Next, I connected a new coin cell externally with an amp meter in series just to check drain on the cell while the charger is unplugged & idle. The meter did not show any drain, but I'm not sure my meter is sensitive enough or if the test was long enough.
I looked for voltage at the battery terminals to see if a charging current was presented to the battery while the device was plugged in. None was present, so my guess is it does not charge the cell. (It might if a load is present, but I did not test that.)

I'd have to agree with what some of you said about the unit being designed for a few years' work & then it is disposable.

The biggest downside in my view is that the end-user does not have any idea that there is a lithium cell inside, so the lithium goes with the charger to the landfill instead of the recycling center. The second biggest downside from my perspective is that it's one more instance of planned obsolescence in our Throw-It-Away culture.

Thanks Again for the great lessons everybody. These innocent appearing chargers got me to do lots of studying about PSUs. ICs & related components & circuitry. Learning's Good!

Enjoy This Day!
Paul
 

tcmtech

Joined Nov 4, 2013
2,867
I decided that experimenting with this charger was way more important than cutting the lawn, painting the soffits, doing brick repairs on the chimney & stuff like that, so...
I can definitely relate to that prioritization concept.
The biggest downside in my view is that the end-user does not have any idea that there is a lithium cell inside, so the lithium goes with the charger to the landfill instead of the recycling center. The second biggest downside from my perspective is that it's one more instance of planned obsolescence in our Throw-It-Away culture.
Lithium is not a dangerous substance.

Do some reading and you will see its everywhere. Even in our food.
 

BobTPH

Joined Jun 5, 2013
8,804
Another possibility is that the manufacturer bought a bunch of defective (or counterfeit) button cells that had nowhere near the capacity they were supposed to have.

Bob
 

Thread Starter

PGB1

Joined Jan 15, 2013
139
I knew lithium was just about everywhere (including in some plant foods, eye glass lenses, fireworks, an alloying agent in some metals, cosmetics and behavioral health medications), but I didn't know lithium ion batteries weren't terribly important to recycle. I've always taken them in with my other recyclable batteries. I'll keep doing it, tree hugger that I am.

I have seen Lithium ion batteries that split open & the mess they make when the moisture in the air reacts with the lithium. One of these chargers had a split cell & was quite a mess inside. A lab at an auto company that I do work for keeps small amounts of lithium in petroleum jelly to prevent moisture from reacting with the metal. If I understood correctly, it's so light that it would float if placed in a container of oil.
Where I used to work, the knuckleheads used to cut open lithium ion batteries & drop them into a jar of water that had a small hole punched in the lid. They'd light the hydrogen gas that came out of the hole. Once the jar exploded before the gas was even lit. Thus ended that particular break time activity.

That's a good point about the batteries being defective or counterfeit, BobTPH.
No two of the coin cells were marked the same & none of them had a manufacturer's name. I do wonder if these chargers are even real AT&T or if they're bootleg all together or. perhaps, if AT&T doesn't pay too great attention to their sub contractors.
 
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