Has anyone tried upgrading cells in the battery pack?

[wrybread]

I have the 9 cell battery pack in my W530, and I get about 1.5 hours of life from it on average. And everytime I buy one off ebay I get similar capacity. I'm guessing they all contain ancient first gen 18650 cells.

I'm wondering if anyone knows how easy it is to swap the cells with some new 18650's?

Guessing it requires a spot welder?

How hard is it to disassemble the battery pack?

I have a good old donor battery pack so no biggie if it winds up in the garbage.