I have a few chargers but i only charge batteries that are sitting every couple months. Even an actual battery tender I don't trust the cheap chinese electronics to leave them plugged in and hooked up all the time.
A friend of mine has one of those ctek chargers. It works with regular batteries too and is nice that it tells you how charged it is and also the battery condition. I'd pick one up the next time i need one and want to spend that money on it.