Laptop Battery Charge Limiter

My 4-5 years old IBM Thinkpad R50e laptop had a software "Thinkpad Battery Maximizer", that software had a feature through which you could limit the battery charge to a specific percentage, for instance, the battery will stop charging once it reaches 40% charge, while plugged in.

Now I wan't to use the same feature in Dell Inspiron N5010, but Dell doesn't give any such software.

Is there any software that can control battery charging ? or is there some way by which we can control battery charging in windows 7

That is really a great software, where from to download it?

Batteries have changed. The new Li-Ion batteries should not be discharged to very low levels, that's bad for their health. You're also not supposed to run it 24/7 plugged in either. Let it discharge to 40-50% minimum couple of times a week and it'll stay in good shape I guess. I have a 2 year old Dell 1525 and its battery has 78% health according to Battstat. People had different practices with NiCad and NiMH batteries that they keep recommending but they actually damage these batteries.