Compared with ordinary commercial motherboards, industrial motherboards are mainly powered by mains; in the case of continuous development of demand and increasing functions, many portable products have requirements for industrial motherboard characteristics. Because the mains cannot be powered by mains electricity outdoors, and the mainboard does not have the charging circuit of the spare lithium battery and the related conversion and switching circuits, it is impossible to directly match the conventional lithium battery to facilitate the direct use of portable products outdoors. Under this circumstance, miniature portable products with the function of charging and discharging batteries on industrial motherboards have become a mainstream model. The desktop POS machine 12V charge and discharge backup battery is specially developed for this kind of 12V mains-powered industrial motherboard to meet the outdoor use of portable devices. This solution integrates related charging circuits, buck-boost circuits, and input-output conversion circuits to achieve The same port has the function of charging and discharging, no need to operate separately for charging and discharging, and the maximum power can meet the power supply requirements of industrial motherboards within 100W.