As I just post I’ve been working on installing a new R51 laptop. While working on this I discover that IBM have an option where you set the level were is starts charging the battery. It also has an auto-adjust feature. Thinking about this I realised that:
* Li-Ion batteries discharge very slowly when not under load and have no memory.
* When plugged into the wall, the batteries are not under load.
* IBM is clever and don’t charge the batteries when the TPs are plugged into the wall. Unless the charge level fails below the configured %.
This probably why their batteries do so well, and actually age very well. The R40 isn’t as clever, but after 2 years of use after some discharge/recharge reconditioning the primary battery still holds 90% of its original charge and the UltraBay battery about 85%, or about 6-9 hours total life. The R50 has a large screen, but a better processor. It will be interesting to see how well that performs.