Re: Completely discharging LION batteries

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I'm using Linux 2.4.20 together with the acpi patches
20021205-2.4.20 on a
Thinkpad T20. If I use two batteries (the builtin and a
second in the Ultra-
Bay), the second battery first gets discharged _completely_
and after that the internal battery is used.

That's normal, but yes it is not the smartest idea to do.

What I'm wondering about is that in the Windows 2000 Help of
the Thinkpad Laptop, IBM advises that it is better to discharge
the battery sometimes completely to refresh the full capacity
at least partly. That advise is completely the opposite of what
I've seen. But it could be an mistake in their documentation or
they could target NiMH batteries.

Interesting informations about Li-ion batteries can be found at 
http://www.buchmann.ca/. It seems to be not available at the moment. But here 
are a few tips from the page:

- Charge the Li-ion often, except before a long storage. Avoid repeated deep
  discharges.
- Keep the Li-ion battery cool. Prevent storage in a hot car. Never freeze a
  battery. 
- If your laptop is capable of running without a battery and fixed power is
  used most of the time, remove the battery and store it in a cool place. 
- Avoid purchasing spare Li-ion batteries for later use. Observe manufacturing
  date when purchasing. Do not buy old stock, even if sold at clearance
  prices.

But there is also a note on the site that a deep discharge cannot bring back I 
higher full charge level. On this list I once found the tip that it should
work. I tried it and my battery was again able to charge to full capacity.
btw: DO NEVER COMPLETELY DISCHARGE A LI-ION! Normal electronic devices can not 
discharge a Li-ion completely. So it should be ok to discharge until the 
device powers of. There is still enough power in the battery to lit a lamp 
for a long time. But that would discharge it definitively to low!

Jochen


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