From: Kevin Jarrett (kevin_jarrett_at_hotmail.com)
Date: Sat Feb 02 2002 - 08:06:50 EST
Disclaimer: I did not write this, but thought it was worth sharing.
Thoughts?
-kj-
>>>
Topic: IBM's incorrect advice for handling Li-ion battery (1 of 1), Read 9
times
Conf: ThinkPad T20,T21,T22,T23
From: viper2001
Date: Saturday, February 02, 2002 04:11 AM
I've just gone thru' this EXCELLENT website with information on how to
maintain batteries:
The online book is free, just sign-in with your email address. In there, the
author compared different types of batteries and how to maintain them.
Accord to him, the proper way to maintain a Li-ion battery is:
- Li-ion batteries perfer swallow discharge cycles. It's best to discharge
80% then perform a full recharge. This is the way to maintain full charge
capacity. Deep discharge will cause the battery to lost full charge capacity
and is not recoverable.
- Li-ion batteries has a shelf life. The cell's internal resistance will
increase over time, and eventually the batteries will no longer be able to
deliver the current. Even if the battery is in storage, this inevitable
chemical process will occur. So it is best not to buy new Li-ion battery and
put it in storage. Best to buy fresh ones with recent manufacturing date.
- If you plan to storage Li-ion battery, the best way is to store it at 15
deg C with a 40% charge. You can store it in the fridge, but not freeze it.
Freezing Li-ion battery will also destroy the battery. Storing a Li-ion
battery with 100% at 25 deg C will cause the battery to lose 20% full charge
capacity in 1 year. Storing the battery at 15 deg C at 40% charge for 1 yr
will only cause the battery to lose 2-4% of full charge capacity.
The fact that if you put a battery in a TP with AC plugged in all the times
means you're effectively storing the battery at 100% charge at 25 deg C. In
1 yr's time, the battery will lose 20% capacity. This is consistent with
what I observed with my 1 yr old T20 battery. Full charge capacity is down
to 31W as opposed to 38.88W (20% lost). I've also done a test on my new T20
battery. Recharge at 8% capacity also does not reduce full charge capacity.
The fact that the battery alarm is set to standby at 3% capacity will cause
full charge capacity lost.
I've also done a test on my X21. If I left the new battery drained to 3% or
1%, the battery will lose about 1W of full charge capacity. I can repeat
this and get a consistent result. If I recharge when battery is at 20%, no
full charge capacity lost is observed.
So what IBM is recommending is 100% wrong. They recommend deep discharge for
Li-ion batteries and store the battery at 100% full charge.
The fact that T20 will not run at full CPU speed (silly Intel SpeedStep)
without the battery is a BIG conspiracy. This means you have to replace your
battery once a yr even if you're on AC most of the time.
For some reason, my X21 is able to run at full CPU speed without the
battery, but not my T20. I hope IBM can release a new BIOS for the T20 so
that I can run at full CPU speed without the battery.
I think that a class action suit against IBM and/or Intel is a possibility
here.
Albert Shan
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