I left this charger plugged in 24/7 for 4 years, and unlike some other garbage chargers, it never over- or under-charged. I started with a couple other brands, including one from "Moto-power" and I was concerned because either it didn't charge when it was supposed to be charging, or else it was over-charging - first time I used the Moto-power charger on a (new) battery set on float, it was charging the minute I hooked it up and still charging 12 hours later! Pretty sure that isn't what it was supposed to do, and not willing to gamble a $200 battery on a bad charger, I got the Cen-tech from Harbor Freight.
![battery charger cen tech battery charger cen tech](https://i.ytimg.com/vi/09ZDG4Rf1iw/maxresdefault.jpg)
![battery charger cen tech battery charger cen tech](https://m.media-amazon.com/images/I/51wZnhYsMyL._SL500_.jpg)
I had to keep up the battery on a 1999 Mercedes that is driven less than 50 miles a year. I've tried several others, this Cen-tech is the only one that consistently works.