I have now souped up my chainsword... Replaced the old homemade battery pack (six 3V CR123A cells) with 18 1,2V Sanyo 1500 cells. This runs the B+D motor at 21,6V instead of the original 18V!
Now this thing is as powerful as I hoped it would be. No more jamming in soft material and such.
Also, the 900 gramm (about 2 lb) "pommel" makes a great counter balance.
Here you can see it next to the old, lame battery pack.