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eftychia: Me in kilt and poofy shirt, facing away, playing acoustic guitar behind head (Default)
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Drained Beyond Zero?

posted by [personal profile] eftychia at 11:29pm on 2004-06-17

I found a handfull of AA cells not in their packaging nor in one of the places where I usually put effectively-dead ones, so I checked them with a meter. Given that I use AA cells mostly in camera flash units, and change them when the flash starts taking longer to cycle than is convenient (usually around 1.3 - 1.4 V (a bit of trivia: a "1.5 V" battery (can I really call it a "battery" when it's only one cell? -- okay, okay, nitpicky and obsolete...), when new, is usually 1.6 V, and a 12 V car battery in good condition and fully charged is more like 13 V)), and hang on to them to give to a friend who finds not-dead-but-not-new cells useful ...

Sorry, I'm feeling kind of scattered ... Anyhow, given the way I use AA cells, I was rather startled to find two that were reverse-polarized. One was -0.3 V and the other was -0.1 V. I'd heard of the phenomenon but have no idea how I managed it with the way I use batteries.

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There are 5 comments on this entry. (Reply.)
 

(no subject)

posted by [identity profile] juuro.livejournal.com at 09:43pm on 2004-06-17
Sometimes it is possible to shock the cell back into right polarity.
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posted by [identity profile] dglenn.livejournal.com at 04:27am on 2004-06-19
Would that turn -0.9V into +0.9V, or would it be part of a recharging operation?
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(no subject)

posted by [identity profile] juuro.livejournal.com at 09:35am on 2004-06-19
What I've done sometimes is take a 100 uF capacitor, charge it to 4..5 times the nominal EMF of the recalcitrant cell, and discharge the capacitor to the cell, at its nominal polarity. Repeat a couple of times, and then recharge.

The procedure will either rejuvenate the cell or render it rather completely hopelessly defunct.
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posted by [identity profile] bkleber.livejournal.com at 05:29am on 2004-06-18
can I really call it a "battery" when it's only one cell?

I try not to, but it's such common parlance at this point that it's essentially a lost battle. But when I tutor circuits, I get to go on about how *every* household battery is made up of some combination of single 1.5V cells, and so only the 9V is actually a "battery" of 6 of them, &c. Hee.
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posted by [identity profile] dglenn.livejournal.com at 04:29am on 2004-06-19
And the 6V lantern battery, of course...

I'm relieved to not be the only one who thinks that way.
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