Can old batteries still be good?

Here is the story. I bought a used Lenovo T500 in January. It came with a battery which I didn't even bother using because I bought a brand new one instead. I just figured the old one would be crap based on the 2008 mfg date on it. Well, I then left home and just came back yesterday. I saw the battery lying there and decided to put it in my computer yesterday. Lo and behold, it seems brand new, even though it isn't. It was made in October 2008, first used in March 2009, and had 25 cycles on it. Design capacity is 56.16wh and current capactiy is 53.6wh. I thought something had to be wrong, so I did the battery maintenance test in the Lenovo power manager, and it all checks out. How is this even possible for such an old battery? I thought that the lithium-ion cells would degrade over time. The battery was made just shy of 6 years ago. It doesn't make sense.

 

It’s just not so. Batteries degrade with charge-discharge cycles. They don’t degrade with mere passage of time (nearly so much as you think). On a now ancient laptop of mine which I had run nearly exclusively on AC power, the battery would retain at least 80 % of its original capacity after eleven years.

As I see it, batteries degrade especially fast if they are often charged and discharged partially at random—as is common in business settings where the clueless or indifferent users just don’t care (to either nearly fully discharge a battery once it has begun discharging, or to fully complete charging once the battery has begun charging).

 

I am running a Dell D610 from that era, I would guess at least 300 full discharges, and still get about 1.5 hours (I used to get 2 hours). But I had to test out at least 10 batteries to find one that lasted this long (I used to work in IT and we upgraded all of the D610's back ~ 2009).

 

Lithium batteries, like a number of other things, operate on a bell curve regarding how fast or slow they lose their charge. The same factors influence the outcome (temperature, charge state, cycles, time), and the majority will have similar charge reduction patterns (down to 80% of maximum after rated number of charge cycles and/or 18-24 months of use, continuing lower as charge cycles and time increase). But there are some that fail much earlier than they should, and others that last much longer than seems believable. It is based on the specific chemical components in each battery, and minute variations can make a difference. You just got lucky and got one of the really good ones.

 

Sanyo batteries usually go bad very fast, LGC can sometimes last a long time, panasonics last the longest for me.

 

The ancient battery I was giving as example is indeed Panasonic.

 

The battery I'm talking about is also Panasonic.

 

I've got two 9-cell Panasonics for my T43p which are from 2006/2007, still hold 80%+ charge after 300/500 cycles respectively.

My QXGA FrankenPad also sports a '08 Panasonic with less than 20 cycles that holds the designed charge.

These batteries were well-made, to say the least. The same holds true for a variety of Panasonic batteries that I've had in my (both work-issued and personal) Let's Note units and ToughBooks.

 

I guess I will stick to Panasonic 18650 cells to fix a few old batteries!

 

Batteries *DO* and *WILL* degrade over time if just left idle. Recent (i.e. In last 5-7 years or so) batteries just don't have the issue if/when you charge it at whatever capacity. You don't need to discharge a battery fully, that's old battery tech. The latest ones are not sensitive to requiring full discharges all the time. The only reason a full discharge is needed in modern batteries is to calibrate the battery sensor. Batteries left plugged in or disconnected will degrade 3-5% per year with no charge/discharge cycles, all depending on quality of the battery material/manufacturing, temperatures, %RH, etc.

An eleven year old battery is likely not Li-Ion but NiCd or NiMH, which had memory issues and required frequent discharge and recharge cycles otherwise it would lose significant capacity. I don't know of any NiCd or NiMH batteries that can hold an 80% charge after 11 years. Even commercial grade batteries have a 7 year max shelf life where they can guarantee the capacity and usefulness of the battery. It's just a matter of physics.

As a matter of fact, I've had a battery that I drained to 40% (recommended for storage) sitting in my basement (below 65F most times) for the last 4 years and soon (4 years in October actually), I will plug it in the laptop I have, do a full discharge and recharge and see what the battery life is then. Compared with the battery that has been plugged in to the laptop for the last 4 years used occasionally on battery, with a couple dozen discharges and recharges.

 

Yes, it is Li-Ion. It’s Compal-assembled BAT30N3L, or Panasonic P/N CGR-B/840AE, if you’re interested.
Rated 14.8V, 3900mAH.
Manufactured most likely in 2002, used since 2003.
If I recall correctly, Li-Ion batteries were already common by then.