This battery cable adapter is to be used with the Respironics 12-volt DC power cord. This product will adapt your DC power cord to allow for a direct connection from your Respironics CPAP or BiPAP machine to a 12-volt, 100AH, deep cycle marine battery. Great if you do not have a working cigarette lighter power source or would like to keep an emergency back-up power source for your home. If you would like to purchase the DC power cord AND the battery cable together for your Respironics machines, please see our Respironics Shielded DC power cord system.Please note: This product must be used in conjunction with the Respironics 12-volt DC power cord. It will not work without this additional piece.