You turn your existing box upside down, undo the screws so you can lift off the lid and replace the two batteries in there with these, once complete and lid back on you use your existing charger, very well made mowers these and keep going so worth messing around and proper recycling. the other alternative is to but one of the brand new pretty lithium cordless mowers and find out the following year that nobody makes batteries for them and have to throw it away.