Stephen wrote:
> On Tue, 02 Dec 2008 12:58:51 -0500, Tom Austin <taustin> wrote:
> 
>> A internal resistance may build due to age, but I think that is 
>> different that what I am referring to.
> 
> Yes, I agree it is different. I'd not heard of a film on the electrode before.

I was using the term 'film' because I lacked a better term at the 
moment.  It's a buildup of 'something'

I got curious and looked up a few sources
I'm not crazy - I actually found something.


apparently it is called a 'passivation layer'

http://www.spectrumbatteries.com/id6.html
http://www.electrochemsolutions.com/pdf/Passivation.pdf
http://www.bealecorner.com/trv900/battery/lithium.html

I believe it has to do with low current draw.
Low current does not burn off the passivation layer that forms, yet you 
do not see much affect because the current draw is low and the internal 
resistance drops little voltage.
But as soon as you need a higher current from a battery with a big 
passivation layer, the voltage drops due to the internal resistance.
Most electronics sense the low voltage and indicate low battery and shut 
off.
If they would stay on for a couple of minutes the passivation layer 
would be burned off and the voltage would return to normal.


I don't know what 'chemistries' of Li-ion batteries have this problem - 
apparently someone thought the SONY Infolithium batters did.




Tom

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