I also have salvaged 6 18650 from notebook battery packs for twice. First set was Samsungs and was ok as they could even supply 3 amps for my XMLs. Only the capacity was dropped from 2000 to 1200 in this set. The second set was in bad condition. I checked the capacities and they were only 700mah. Two were over heating while charging and regular chargers didn’t finish as they should. Just check if any of the batteries you gained heat in the charger. I was lucky that it didn’t set the house on fire.
Last December wanted some free unprotected 18650s for my Ebay portable USB charger so I resorted to "Dumpster Diving" several battery recycle bins. Scavenged several Dell, HP, Acer and Toshiba laptop batteries about 10 total. First rule is don't waste time on any pack over 3 years old. Second rule is after disassembely of packs, discard any battery with less 3.0 volts. Although it is possible to get usable batteries by NOT following rules 1&2 generally 90%+ are junk. My total yield from 10 packs less than 3 yrs old was 24 execellent batteries. 6 Sanyo2600 that checked @ 2450+ma, 6 Panasonics 2200+ma, 6 Sony 2200+ma and 6 Sanyo 16650s 2000ma. Had several batteries (8?) that were older low spec 1100-1200ma. Took the bad ones back to the recycle bins. IMO this is true recycling. YMMV
Our firm has an old battery collection point to recycle and this is just in front of my door. There sometimes people leave their used up alkalines, old cellphone batteries and laptop batteries. I once found an almost new Nokia battery that I still use. If a laptop battery is dropped there, I kindda fly over and loot it at once. I once had 6 Samsung batteries with 1500mAh measured capacity (at 1A) those can still push up to 3 Amps for my 8xAMC lights. The second one was a bit poor, 6 Sanyo batteries with 800-1000mAh capacities left. The last time was a surprise. A small battery pack had 9 Sanyo batteries, 6 totally exhausted, with 800mAh capacities left, but 3 were very good indeed, with 1800mAh capacities measured at 1Amp discharge.
It takes some time to measure and mark them all but it is a good effort that pays you 3 good batteries out of nothing. I now use the exhausted ones in a 3x18650 SolarForce L2 fitted with a 3-18V XML drop-in with 400mA tail current for 12V giving 2 hours of 400 lumen light, while the other three make a good working set for stronger lights.
While measuring their capacities I also charged them with my Accucell 6 balanced charger. As normal, after reaching the 4.20 V barrier the current drops and the process turns into a constant voltage regime, but the strange thing is, the battery seems to heat up a bit at this point and the current rises again. Ok it doesn't heat up to dangerous measures but it doesn't seem to be safe to charge these old batteries overnight either.
but in a similar vein, there are several u tu be vids on reviving sub voltage rechargeable bats. i have tried it on aa nicad and i'll be damed if the bat didn't take a charge and come up to the rt v. i haven't done any more experiments on different bats because i didn't have any, but i plan remember after i accumulate them.
4 recessed torx screws, sometimes with the security pin so it might be necessary to cut through the housing and screws to open it up. Then just desolder the charge balance/protection/dock board and snip the nickel plated connection strips.