This is the design I've shown and discussed
elsewhere, now realized in non copper-clad-prototype form as well.
Powerful enough to suck down an 18650. Not sure if these cells are in need of a charge, or just old and weak, but I'm only getting 50% of rated power out of these. Nothing wrong with that, of course -- the undervoltage limiter circuit prevents brown-out failure. That's why I know I'm getting only 50%.
Very hackable design. Lots of test points. Two resistors change it to a portable, adjustable bench supply!
Tim