The smart tweezers are operated with alkaline button batteries type L736H or AG3 (dia. 7.8 x 3.4mm). To replace the batteries unscrew the battery and light compartment with a coin on the upper side of the smart tweezers (you see a button with a slot in it). Remove the old button batteries and insert the new batteries with the negative side pointing forwards. Screw the battery and light compartment back on.