I can well imagine that low quality cells are the major worry, but what I’m reading by people far more knowledgeable than I am is making me nervous.
Look at this for example:
“If say your battery terminated at 4.2v [ Normal ] , and after one hour is still holding 4.2v , then your battery is in good shape . If say the battery drops to 4.19v after one hour , then this is rather normal , as would be 4.18v , well within acceptable levels of voltage sag after charging .
Now lets say the battery sags to 4.15v after terminating at a measured 4.2v , then the battery quality - condition is really not so great , and is showing sign of more internal resistance than should be considered normal . If the battery were to sag to 4.12 or lower , then I would suggest replacing the battery or keeping a very close eye on it . ”
Scource:
http://old4570.com/extra/batterywarning.html
What strikes me about this is that we are talking about just hundredths of a volt. The tolerance margins seem slim.
Multi-cell lights appear to be a particular problem, needing a Digital MultiMeter to take battery voltage readings.
You raise an interesting point about laptop batteries.
In order to remain “on topic” without veering off too much, it looks to me as if Li-Ion is still very much the favourite, but that Nickel certainly has it’s supporters, and there may be fertile ground for a certain smallish level of drift away from Li-Ion.
What type of percentage increase in AA cell capacity and brightness are we talking about?