Having worked at a battery shop we sold this line of chargers. Many shops and garages bought them with little return or defective. It's not the best, but this little home unit would probably last you forever in home usage. Everyone needs a unit like this.
You might also consider instead getting a jumper box. This will allow you to jump your mower, car, or whatever immediately without having to charge the battery first. I have also left the jumper box on a battery all night (plugged in to the AC) so as to trickle charge the dead battery through the jumper box charging circuit. It works great.