I just got an e-mail from a friend who bought two C-Tek chargers a while back. One quit and he said that the company really couldn't care less. I haven't had problems with the ones I have in the garage. Time will tell I guess.
I think what they mean is that it will maintain a bigger car battery but wouldn't be good for charging one from dead. The ones I have are the Multi US 3300. It has settings for big, small batteries etc and did charge a battery that was so dead that the interior light wouldn't even glow. Over night and it was good to go. The one advertised is the cheapest in the C-Tek line. If memory serves me correctly, I paid about this same price for our 3300 series units last year when CTC was getting out of them. http://smartercharger.com/battery-chargers/