Over a year back, the writer have see some IBM fans complain that their battery is disabled between 1 year to 2 years of usage, even it still last more than one hours before it fail. Actually, many branded battery only last less than 2 years nowaday, not just IBM.
The IT product become cheaper and cheaper over the years, silicon chip is one that can be done much more complicated but at the same surface area. But battery isn't one that advancing so quickly, reducing the cost can somehow related to reducing of the raw material usage like reduced Cobalt used, which in term will reduce the usable duration.
What the writer found out and assume that, the battery lock the power input and output to prevent it from overheat! The manufacturer have learn the lesson from history, if you want to use it till last juice, it is more tend to show a phenomenon of overheat after the cell lose balance in state of charge. They usually only give one year waranty to battery, promising customers within what they can do is better that promising customer something that is more risky and impossible.
The writer have try to discharge a T61 battery produced year 2008 which not more usable after it have been use 174cycle, which stay at near 100% but not functioning.
See it still manage to discharge 2436mAH (note, it do not hold 100% at the beginning, since it is start discharge at around 12.4V), it rise back to ~3.7V per cell after it reach end of discharge, cell 1,2 reach 3.2V, cells 3 reach 3.0V. So it is not manage to output most of the power it have. The right picture, that is what the curve of end of discharge a new cell look like. One thing the technician manage to notice, the cells is self-balanced if user let it rest some time before recharge it, there have not clear proof of this, but user can try this to pro-long their IBM battery life.
Purposely charge it a while (blue circle) to turn on the battery and allow it to discharge again, See the cell have different voltage 3.36V, 3.401V when discharging, but this time it is more balanced after it do self balancing.
See, another 355mAH discharge, this mean the cells is not in real empty, just that it impedence is too high to output all the energy it suppose to deliver. This time it reach lower end of discharge voltage than before since the cell is self balanced. But still green circle show that it it around 3V for cell 2,3, 3.225V for cell 1 (which mean it have slightly different capacity). This could be the reason why the battery lock it power output itself.
UPDATE: 04thSEPT09
Customer feedback, a picture worth a thousand words...
"Battery been discharged completely once and fully recharged. So far so good."
For those advanced notebook with many feature and more graphical power, 2 hours is really good enough. Some older notebook without so many power hungry feature can last 3 hours plus or more, don't worry.
UPDATE: 30thSEPT09
Lenovo X61 series also can be fixed now, no problem. 100% can be realt if ur battery still can be used. 90% above if can not used anymore.
