Do you need to opperate a CPAP or Bi-level machine from 12V battery with exposed terminals? When connecting your CPAP or Bi-Level machine to a free standing 12 volt battery, there are 2 required cables. The item pictured is a 12v battery adapter cable. This battery adapter clamps directly to your free standing batteries positive and negative terminals. The other end of this cable connects to a DC Shielded Power Cord, which then connects directly to cpap or bipap machine. Although this 12v battery adapter cable is made by Respironics, it is universal and will work with any brand machine. The DC sheilded lighter style cord however is machine specific and looks like this: If you do not already own the DC shielded cigarette lighter style cord you will need to first determine the model machine you have. Please look on the top or bottom of your machine to locate your model.DC shielded cigarette lighter style cords: Older REMstar cpap machines: Click Here Respironics M Series CPAP Machines: Click Here Respironics PR System One 50 Series (DS150,DS250,DS450,DS550,DS650,DS750): Click Here Respironics PR System One 60 Series (DS260,DS460,DS560,DS660,DS760): Click Here All ResMed S8 CPAP Machines: Click Here ResMed S8 VPAP machines (VPAPS,VPAP ST,VPAP Auto,VPAP Auto 25): Click Here ResMed VPAPIII ST-A: Click Here All ResMed S9 CPAP and VPAP S and VPAP Auto: Click Here You can use any 12V battery that have their battery terminals exposed. A car battery can be used, however a deep cycle marine battery is the best choice.