A battery unit includes a housing, an electrode core, a first electrode terminal, and a second electrode terminal. A chamber is defined in the housing. The electrode core is arranged in the chamber, the electrode core includes a first electrode tab and a second electrode tab, one of the first electrode tab and the second electrode tab is a positive electrode tab, the other one of the first electrode tab and the second electrode tab is a negative electrode tab, the positive electrode tab is physically and electrically connected to the housing, and each of an end of the first electrode tab and/or an end of the second electrode tab away from the electrode core includes multiple connection pieces spaced apart. The first electrode terminal is electrically connected to the first electrode tab. The second electrode terminal is electrically connected to the second electrode tab.