You say .focus does not want to know, So from that, I would say over 5yrs old, as that is the time limit for service on equipment, They only need to provide service parts etc for about 5yrs after end of sales.
I would say have a look at other drills, some are probably the same size and fit. Most drills etc whatever the make, the battery packs fit similar. Other thing, Something I would do, although not recommended, is pull the thing apart. the packs are made up of several 1.2v cells for a 18v pack, 15 cells, the problem is connecting them, they are dot welded. You may find that if you open it up, only 1 cell is faulty, so replacing that 1 cell, will get it back to normal. Another thing you could try is to cycle the battery. Connect a lamp across the terminals, to discharge it fully, (normal use does not do that) then charge fully, Then discharge it fully, and repeat. You might need a few goes, But sometimes works, and gets the battery back to full operation. I have done it in the past, It works sometimes.
SD, August 2012