Niles H.

I've heard a similar figure for lithium-ion batteries -- three or four years. But it depends on a number of factors, including the manufacturer and model, and the storage conditions. When stored at 40-60% charge and under refrigeration, IIRC, they can last much longer.

Apparently Toshiba and others have the ability to make longer lasting lithiums.

I have heard that some of the high-charge-rate lipo packs do not have terribly long cycle lives and shelf lives, but I haven't yet come across hard data on this, and some of these sorts of packs are fairly new on the market.

Sanyo NiMHs do have clear, multiple independent reports of surprising longevity. I wouldn't be too surprised to see these go twenty or thirty years, with proper care.

Laptop batteries are typically just lithium-ion 18650s connected in series and encased in plastic. I verified this with a couple of old packs I found for a dollar. Sometimes these are recycled by Chinese sellers of cheap 18650s. It's a crapshoot -- some are fine, others are DOA.

It would be interesting to survey a series of computer techs, or just ask a few of them how long they've seen laptop batteries last. They seem to do pretty well at times.

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If the shelf life of a particular battery model were so short that you would only use 10% of the available charge cycles, then you could fast charge even if fast charging shortened the cycle life considerably, and still not lose out. The shelf life would be the determining factor, whether slow charging or fast charging -- as long as the fast charging didn't shorten the cycle life too severely.

At the other end of the spectrum, there are some batteries that do seem to have the longer shelf lives.