testing lithium coin cells

 Stepped on the scale one morning and it started blinking Lo  rapidly.  Time to replace the two CR2032 lithium coin cells:

But I found this in the drawer:

Is this OK or what ?? (yes, I know there's such a thing as written notes but it wasn't done, OK ?)

Now I usually use the old reliable (sorta) Sears VOM for this:

in fact that's about all I use it for.  But it's not helpful in this case.

Looking at the Energizer data sheet for CR2032 I saw this figure:

For a load resistor of 30,000 ohms the voltage is very constant at just above 2.8V and then it falls off the table like a Koufax curve ball.  So why not a simple test fixture and the DVM to test the CR2032:

It's just a wood clothespin with a small 2-56 bolt through each side, wired to a 10,000 ohm resistor (1 % for some reason) and with two flying leads to the DVM.  Let's try it out, first with the bad cells just removed:

they are both below 2.8V.  Next try the unknown cell:

It is above 2.8V but just barely, the graph indicates 2.85V or so as good but this is with a load of 30,000 ohms (I mis-remembered the resistor value when making the fixture).

I had previously put two new CR2032 cells in the scale so it's not super important but at least now I have an idea of what the scale thinks a bad cell voltage is.

BTW, later I did retry the measurements (although no pictures) with a 27,000 ohm resistor as a load, the measurements were a little higher but ultimately no big difference: 2.728V, 2.743V, 2.839V

Best Regards,
Chuck, WB9KZY
http://wb9kzy.com/ham.htm