How do you tell that a 123 cell is almost dead?

[AlexGT]

Hi all!

I have several regulated lights that use regular lithium 123's and would like to know how do you tell if the cell has lost its useful life, I wouldn't want to end up with a dead light in the middle of something important.

I have a battery charger that displays voltage and a used regular lithium 123 (Not li-ion) is showing 2.87 Volts. How much juice does it have left? 50%, 40%, less? just to have an idea.

Thanks!
AlexGT

 

[andrewwynn]

you need to test it under load. I'm not sure the % dead... but usually no-load voltages don't help very much... i load up my batteries with a 1ohm or 1/2 ohm resistor and measure the voltage they hold.. then i can bin them to re-use the 1/2 empty ones that i'm not happy with anymore (at about 1/2 empty they won't run my lights on high-beam anymore).. that also can be a very good way to tell.

 

[winny]

EDIT:
Removed everything. My conclusions where all wrong.
If you can apply a known load, you should be able to tell how much there still is using the carts in SilverFox 123 battery shoot-out.

Ask SilverFox. He does know for sure.

 

[andrewwynn]

hey that's really smart about known load and compare.. better yet.. since the 'known load' in order to match those charts.. needs to be a known CURRENT load, not resistance.. the likes of simple LDO driver and resistor that will draw 'at least' say 1A.. that would do a very good job.. all you need is silverfox's chart.. a voltmeter and a 1A or 2A LDO driver and a resistor.. a pretty simple circuit could be made with PIC that would be able to be programmed with that graph and convert the votlaged to a bar-graph of charge remaining (over my head of course)..

-awr

 

[glockboy]

Get the ZTS Mini_MBT tester.
http://candlepowerforums.com/vb/showthread.php?t=130104

 

[AlexGT]

Thanks for the replies, I'll look into silverfox charts.