It's probably better for lithium batteries
Got this cause I bought some random tools off an auction and there was no charger for the 2x batteries and 1x drill. This will charge Ni-Cd batteries until it reaches 20-21V and then it stops completely. You can leave it in the charger while the battery drops to under 18V, more like 16-17V and it will not detect that drop and leave it in that state without charging it back up. That only happens if you are trying to resurrect a NiCd battery from the dead, and the internal resistance of the resurrected battery burns through the stored energy until it is done being resurrected, although it is better to burn through the charged battery immediately to get more capacity back. Battery university has an article on NiCd restoration against the memory effect crystallization . I believe you need to make the battery at least 6V for the charger to detect it through any means, as long as you don't burn the house down.
This charger probably will work far better with a lithium type battery as there are controllers on the battery, while the older NiCd batteries are dumb batteries with no charge controllers. It will say fully charged in around 5-10 minutes, which is a complete lie from a capacity standpoint, based on NiCd batteries. You can also re-insert the battery quickly to sort of top it off, but it's probably still better to burn through the battery and recharge it again.
If you guys can, try to buy this charger for under $15, including shipping+tax, cause it is definitely not worth tossing out $20+ for something like this. And also especially because it appears the SB18 style batteries look like they are being phased out for the pwrcore 20V type ones.
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