There is no soldering to make this extremely easy tiny battery tester..

You can keep the tester in your very smallest pocket..

Take a careful look at Battery caused LED brightness.

And there are other uses for these component parts.

Step 1: Parts

Picture of Parts
Wondermagnet.com supplied the NdFeB Neodymium-Iron-Boron Rod magnets for this project.

Top  magnet  ¼"dia × ¼ "long rod
Base magnet ¼"dia × ½"long rod

Safety Notes

Please do not let little children play, mouth, or risk swallowing these attractive magnets,
a serious surgical situation may result if swallowed.
Also take care to restrict access to  the little button batteries which may contain mercury.

I take no responsibility for any mishap, or injury that may result or occur now or at some later time because of this project..
Phil B3 years ago
Is this a "go/no go" tester with no gray areas? I have used some coin batteries that seem to have a threshold below which they do not power the device, but still seem to have quite a bit of life left for other uses.
iceng (author)  Phil B3 years ago
This LED battery tester is more then a "go no/go" pictures 4, 5 and 6
in the first step are different battery conditions with different
LED intensities. 
You very are correct some applications can use the last dregs of
a coin cell like a Joule Thief light verses some radios or hearing aids
I have known.

You know our eyes respond logarithmically to light while the LED is
more linear to battery energy near its end of life curve and depends
on battery type.  That is a reason why the electric meter came about.

This tester in the best use is a comparison of the same type of coin cells.
I can easily grade a group of cells to eight levels if I put my eyes to it.

Then the magnets in the plastic compartments try to hold the cells from shorting each other out.

canucksgirl3 years ago
Looks rather handy to have. Thanks for sharing. :)
iceng (author)  canucksgirl3 years ago
Happy to do so :)

Are you going to award patches for total views for  Jayefuu and HQ

Date Joined
Hey... who told? lol

I've been working on several new ones actually including total views. Jayefuu likes that one the best right now, so I have to try and up the ante... hehe
iceng (author)  canucksgirl3 years ago
Well.... I follow you both and can read
the lines as it were..
Mighty sly of you....

I best watch what I say between the lines as it were... :)
BLUEBLOBS23 years ago
Very interesting! Both useful and compact!
iceng (author)  BLUEBLOBS23 years ago
Thanks for the nice comment.