The one I'm using is the Schumacher Speed/Charger (maintainer/mantener).....sem1562a 6v/12v
At first I didn't think it was working but it turns out, that at that time (4 months ago) I wasn't using enough salt and the spoons were not right. Now everything works great. I do get a little concerned at how much red sluge is coming out, even after 8 or more baths and doing the alternate polarities really speeds it up. I would think other things would start showing up besides the small amount of black stuff and gobs of red. There is a little off white stuff that floats on top during and after the bath but it settles to the bottom after awhile. I always let it settle so that I can check for any new stuff.