Could my old battery really be in such good shape?

[hobbes]

I recently purchased a T42 and was able to pull an old battery out of storage to use in it. The battery was from a previous T40 I had and the battery was a backup that was never used. Plus I haven't had the T40 in 2 years, so the battery hasn't been used in all that time.

After putting the battery in my T42 I charged it up and checked the battery health. I was surprised to see the following:

Full Charge Capacity: 46.74 Wh
Design Capacity: 44.00 Wh
Cycle Count: 3

First Used Date: 2003-07
Manufacture Date: 2003-06-04

I thought Li-ion batteries degraded over time. How is it that a three-year old battery that has been stored at room temperature and not used at all can have such a good capacity? Can this battery really be as healthy as those numbers would indicate, or am I missing something?

[christopher_wolf]

Yeah, I have had some old T4X batteries, from around the time of the T40s and T41s, sit in storage up until a year ago when I first used them. They happened to be in pretty good shape despite the age. It depends on how much use they had and how much charge they had when they initially went into storage.

[terry_mccann]

Well, easiest answer would be to let your notebook run on the battery and see how long it lasts....would be interesting to know.

[bigtiger]

I have had similar stories on my X24, X40 and T41. I think cycles count more than the first usage.

[underclocker]

After a couple of rundown cycles below 10%, the battery may adjsut. I've seen this happen, too.

If, however, the capacity remains high, congrats.

[Rose]

try maxing out your thinkpad with something performance-intensive on both your cpu and your graphics. Most probably your battery wont hold its voltage for as long as predicted and it will drop its remaining power in just a matter of seconds.

[hobbes]

Well I ran it on the battery with some moderate use and web surfing and got a little over 2.5 hours out of the battery. The capacity numbers have changed a bit:

Full Charge Capacity: 46.74 Wh - now 41.38
Design Capacity: 44.00 Wh - now 47.52

I'm going to give it a full charge again and check the health one more time to see what I've got. Will those numbers keep changing if I do the test multiple times?

Seems to be a good healthy battery though. I'm a bit surprised.