CR2 Lithium Battery

dealgrabber2002

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Hello,

I found a bunch of used CR2 lithium batteries at my work place. I took it home and measured it and most are at 2.7-2.8v. Are they still good to use? Dangerous? Thanks.
 

LogicalBeard

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Are they lithium primaries or rechargeables?

Primaries can be run down to nothing, which is what I suspect you have.

Rechargeables are when it can get a little tricky.

Out of curiosity, what light are you using them in?
 

WalkIntoTheLight

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Should be fine, though I'm not sure what would happen if one got reverse-charged in a series application. Your light would probably turn off long before that happened.
 

zipplet

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If you are using them with a spacer in a CR123 light, please be aware of maximum current draw. Only use the light on low modes. Also only use a single cell.
 

LogicalBeard

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If you are using that Surefire L1 Gen5 you posted about that has a high mode of 22 lumens, then I think the high mode is safe to use. Duracell Cr2 batteries have a 1000 mAh maximum continuous rating: I'm assuming you are pulling less than 50 mAhs? But I have no idea about using two batteries at a time. Like WalkintotheLight said, if the voltage/capacity is mismatched where one battery has more capacity than the other, you can run into serious problems.

The name brand of the battery makes a difference and I'm sure you know to inspect the batteries for physical damage too; no tears in the wrapper etc.
 

magellan

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Yea, I am using it in my L1 gen 5. They are Energizier. I did check for physical damage

Okay, thanks.

As Zipplet said, probably okay for light duty, and avoid 2xCR2 configurations, as those can be problematic for old, aging, or otherwise unequal cells.
 

LogicalBeard

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The nominal voltage is 3 but they actually start off somewhere around 3.27

At 22 lumens, I bet you still get some useful runtime out of them.
 

WalkIntoTheLight

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At 22 lumens, I bet you still get some useful runtime out of them.

He will probably get about an hour runtime out of them, maybe two, at that output. Not great, but okay. IMO, I'd just use a rechargeable RCR123 in that light, if it can handle 4.2v. It will probably give him 10x the runtime.
 

dealgrabber2002

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One of the battery did 7 hrs on low. Still the same brightness from start. Haven't try high yet.

I use 3.2v lifep04 in my L1. Just found all these batteries with some juice, just want to make them useful.
 

archimedes

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You can take a look at the Energizer CR2 spec sheet, if you like, to get an idea of the voltage curve under continuous load ....

Just guesstimating based on that, it looks like a ~ 30 mA drain will run ~ 35 hrs total, dropping from ~ 3.1V to 2.8-ish V within first hour, then a further drop from ~ 2.8V to ~ 2.5V over the next 30 hrs.

Pretty empty past that, with voltage falling from 2.5V to < 1.5V in the next 5 hrs.
 

WalkIntoTheLight

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You can take a look at the Energizer CR2 spec sheet, if you like, to get an idea of the voltage curve under continuous load ....

Just guesstimating based on that, it looks like a ~ 30 mA drain will run ~ 35 hrs total, dropping from ~ 3.1V to 2.8-ish V within first hour, then a further drop from ~ 2.8V to ~ 2.5V over the next 30 hrs.

Pretty empty past that, with voltage falling from 2.5V to < 1.5V in the next 5 hrs.

That is under load, though. He's measuring the voltage at rest. 2.8v resting is probably pretty close to empty. 90% drained? I dunno, could be more juice left in it that what I'm guessing. Only way is to run a test and see.
 

archimedes

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Yes, measured under load.

Open circuit voltage is not especially informative for state-of-charge in lithium primaries (due to passivation, among other reasons)
 
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LogicalBeard

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Good point. I have a ZTS battery tester and a Fluke 117 multimeter but I never test under a load with the fluke. How many ohms do you recommend for a load on a CR2?
 

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