I think an upcoming patch is meant to greatly improve this, at least judging by this, aside from solving the boot parameter requirement issue: https://www.reddit.com/r/thinkpad/comments/4c6q6w/fixing_int...
> I have finally compiled a patched kernel myself and couldn't be happier with results. Not only battery life increased (~1 additional hour), but what's more important, performance on battery improved significantly.
(Note: I have not tried this myself yet...maybe this weekend)
Some other possibly useful links I just came across related to this patch:
- https://www.reddit.com/r/thinkpad/comments/4d6qj5/psa_linux_...