# 3v primary lithium cell - what voltage = dead?



## copperfox (Mar 25, 2008)

I searched for the answer, but for such a seemingly simple question I cannot find the answer!

A brand new primary lithium 3v will register about ~3.2v on a voltmeter, correct?

The reason I ask is that my new Novatac is acting very strange. I pulled the Duracell out and it measures 2.85v. When I put a new surefire cell in, the light acts normally. 2.85 isn't fully depleted, is it?


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## Raymond (Mar 25, 2008)

https://www.candlepowerforums.com/threads/67078

In the graphs, you can see most batteries start to drop real fast (=depleted) at around 2.5V under load. So if you can check your battery under load, you can find out real quick if it's still good.


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## cave dave (Mar 25, 2008)

Its hard to use a voltmeter to determine capacity of a lithium battery, but yes 2.85v can indicate a fully depleted battery.

Your novatac has a better battery capacity detector built in then almost anything you can buy so when the low battery warning kicks in its time to toss it.


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## mdocod (Mar 25, 2008)

Keep in mind that the volt meter has a practically non-existent load on the cell, so after the cell rests for a few moments, it's open circuit voltage can rebound to around 3.0V, but as soon as you put a real load on it, it can drop to a fraction of a volt. Which of course, causes the light to be very dim  Different types of cell chemistries behave differently when it comes to this, Alkaline can be tested with open circuit voltage to get a rough idea, but lithium primary can not. Li-Ion however, CAN be voltage tested to get a pretty accurate idea of state of charge.


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## copperfox (Mar 25, 2008)

You learn something new everyday, thanks guys. I guess the Novatac is now my CR123 tester.


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