How to test button batteries for power. Without Multimeter. 

It might work, but it doesn't tell if the battery is weak or fully charged. It' important since charged batteries are held sometimes for a while and weaken and perhaps the button battery is put into something more crucial - like a car key fob to start it.

Thanks for the video

It is usefull vedeo .It is what light and what volt tell me .

3:00 testing batteries.

where to buy that tester ?

Please be mindful that the button cells come with two different voltages. 1.5V or 3.0V. You know nothing about this and come out with this misleading video.

Crap!