Quote:
Originally Posted by AnotherCat
That is the nub of the matter for ereaders and can be easily shown by looking at charge cycles.
Lithium Ion batteries are usually claimed by their manufacturers to have a usable life of 500 or more full charge cycles. Even if one goes mad and says that an E Ink ereader gets the equivalent of 1 full charge per week (for example, one 30% charge and one 70% charge in the week) then the battery is claimed to remain usable for 500 weeks, say 10 years.
My experience is that the 500 charge cycles is conservative and I suspect that most ereaders need charging less frequently than I set out so it seems that in the above simple look there is little need for ereader batteries to be user replaceable as on charge cycles one can expect a life greater than 10 years.
But I suspect for most people their ereader battery life will be time limited through aging or left discharged or close to discharge, so that the battery is damaged by self discharge taking it into full chemical discharge, rather than ever reaching the full number of charge cycles.
An interesting case is Citizen Eco-Drive watches, for example, as they are claimed to be able to run for 6 to 12 months on a charge without solar charging in that period. So if one takes the recharge period as being 6 months, for example, and the battery manufacturer's specified usable charge cycles (500 if I recall correctly for the Panasonic batteries that have been used) then one comes up with a battery life of 250 years based on charge cycles. Of course the batteries last very much less than that if only just through aging issues.
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And what do the same manufacturers claim for a lifespan time? For example, one of my lion devices is about 3 years old, and it appears its life is decreasing dramatically, and it probably goes through about one charge cycle a week.