There is a tiny watch size battery cell on power board, top right side (view from LCD side) under top cover. Little challenge to replace as it's really small and It is welded to a two flat steel lines (not soldered). Not sure the voltage as mine is also dead and shows 0.6v and it has no any markings on it. Could be around 1.5v but can also be a 3v. But seems that there is an extra room around for a larger size cell may fit.