The instructions caution you not to overcharge the batteries as you may damage them and provides guidelines for the charging time for specific batteries, but the product does not shut off when the batteries are charged leaving you with the hassle of starting the charge cycle only when you can be sure that you will be able to remove them from the charger in a timely manner. Additionally, the 1.5 volt batteries only charge to about 1.3 volts.
Product is a simple and easy way to charge and recharge up to four AA bateries. This product was recommended by the maker of my golf GPS unit. Since the unit only needs two batteries at a time I always have a spare set charged and ready for use.