If you have batteries that are only slightly discharged, this product will work properly and will turn off when finished. However, if your battery is very low, this charger will literally weld the battery together. I tested this on 30 12V 9AH batteries in different states of discharge. He didn't try to charge batteries with a voltage below 8.5 (which he shouldn't, since the battery is chemically altered and destroyed). Batteries between 8.5 volts and 11 volts got very hot and the first one Iโฆ