have an 18V 2.4AH battery pack for Ryobi power tools that will no
longer take a charge and that the charger indicates is defective.

I've taken it apart and found that it has five pairs of cells that are
labeled:

"LS IMR-18650BB
YT0288.different numbers on the ones I can see Made in China"

I see on line numerous variants of the 18650 cells with various mAH
ratings but nothing with the "BB" suffix.

Four of the pairs of paralleled cells show a voltage of 4.1x; the other
pair shows 2.1mV.

Is it worth the effort of trying to replace the defective pair, or is
there a way that I could try to restore them to life?

If I want to replace the defective pair, I assume that any 18650 cells
with at least 1200mAH capacity will work -- but in fact I don't see any
that low.

I don't have a spot-welder. If I use a Dremel cutting wheel to cut the
tabs on the defective pair, would it be OK to solder new ones in place
using copper flashing?

Perce