I wouldn't do that. Always match. It's a real problem with rechargeables. They 
will self-discharge at a different rate than the others, and they won't be used 
equally. I see that all the time and am meticulous about keeping 'matched 
sets', and even then, one will discharge differently and I'll either charge it 
separately for a few times (it often helps) or turn a 4-set into a 3-set and be 
done.

Sanyo has a new series out called Enerloop (I think - or something like that) 
that keeps a charge for years - a few % per year loss. It might be a good 
candidate.

The reason might have been it wasn't matched in packaging (an older cell got 
put in perhaps by a worker in China) or it had a defect, or maybe, since there 
was corrosion, there was moisture and the physical configuration gave that cell 
a watery discharge path from condensation or rain or such.

A couple mA a day makes the charge go away... ;)

-Skip


Jinx wrote:
> 
> Well, as sure as you can be about any battery these days. It does
> say Made In China, and came from the same blister as all the others
> that didn't suddenly go flat. They seem a reasonable weight compared
> with carbon-zincs and other alkalines. If that's anything to go by. I just
> don't know whether to feel insecure, as I've seen this many times with
> NiCd but not an AAA pack
> 
> I've put a new one in place of it, left the other two and will monitor
> what happens to them
> 
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