On 12/10/2015 08:22 AM, Clifford Heath wrote:

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

18650 is the physical geometry: 18mm diameter, 65mm long, 0=round.

Any Li-ion 3.7V 18650 will do as a replacement (peak charge voltage
4.2V) - but get a matched set of 5.

If I have to get a matched set -- of ten (five *pairs*) -- rather than
of two, I might as well get two 4AH ones for $99.

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

It's meaningless as far as you're concerned.

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?

No. Replace the lot - you don't want a mis-matched string.

See above.

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?

Buy replacements with tabs on. Soldering can damage the cell internally
unless you're very skillful and swift.

Avoid Ultrafire and other *fire Chinese brands and their Chinese clones
(often repackaged dead cells). They make fantastical claims of capacity,
but you're lucky if you get 1000mAH, and never as much as 2000mAH (they
often claim 4000 or 6000; no-one can build that).

If you can afford it, buy Panasonic NCR cells - about $12-$15/ea - which
if genuine will produce about 3400mAH at a much better sustained
voltage. Chalk and cheese against the Chinese cells.

Clifford Heath.