Quote:
Originally Posted by rgeorg
Am I correct in remembering that it is good to discharge lithium batteries all the way about once a month, or perhaps once every 10 charges on the long-life batteries?
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Nope. Lithium batteries should never be fully discharged, even under normal use. You can ruin a Lithium battery by doing deep discharges. I don't remember the source, but a few years ago I read a very detailed writeup by a major battery manufacturer about the proper charging of lithium batteries. They specifically warned against deep discharging.
The practice of periodically deep discharging rechargable batteries comes from the days of NiCad batteries, where it sometimes helped with what was called "memory effect". The newer NiMH batteries are not prone to this "memory effect" and don't require periodic deep discharge. Although not needed, I understand that this practice will not destroy a NiMH, as it will a lithium.
Lithium batteries are usually rated about 1000 recharge cycles. From what I read, a partial recharge only counts partially toward one of these recharge cycles.
From my own experience with cell phones, which I charge every night, I typically get 3+ years before the capacity of the battery drops significantly. The battery is not dead, but it no longer has the capacity of a new battery. If you take the 1000 hour figure and divide by 365 days, you get 2.74 years. From this, it seems that the 1000 hour figure is probably conservative.